Review

Degradation of β-carotene during fruit and vegetable processing or storage: reaction mechanisms and kinetic aspects: a reviewCaroline PÉNICAUD, Nawel ACHIR*, Claudie DHUIQUE-MAYER, Manuel DORNIER, Philippe BOHUON

* Correspondence and reprints

Received 30 June 2010Accepted 3 December 2010

Fruits, 2011, vol. 66, p. 417–440© 2011 Cirad/EDP SciencesAll rights reservedDOI: 10.1051/fruits/2011058www.fruits-journal.org

RESUMEN ESPAÑOL, p. 440

Article published by EDP Scien

Degradation of β-carotene during fruit and vegetable processing or storage: reactionmechanisms and kinetic aspects: a review.Abstract — Introduction. Food processing significantly lowers the quality of fruits and vegetables, whichis a major concern for the food industry. Micronutrients are particularly affected, and among them β-carotene,which exhibits very interesting sensory, nutritional and biological properties. The literature concerningβ-carotene degradation is extensive, but the conclusions are very different as a function of the biological,chemical and food transformation points of view. This paper proposes a synthesis of complementaryapproaches in the study of β-carotene during food transformation and storage. Degradation reactions.Degradation compounds are numerous, including isomers, epoxides, apocarotenones, apocarotenals andshort-chain cleavage products, among them some flavour compounds. A detailed reaction scheme of iso-merisation and autoxidation of β-carotene could be deduced from the literature data. The main pathwaysare well documented, but the global reaction scheme is still incomplete. Furthermore, most of the mechanisticstudies are carried out in model systems, thus data may misrepresent β-carotene behaviour in real food pro-ducts. Kinetics during processing and storage. The determination of degradation kinetics permits theidentification of the fastest reactions, i.e., generally those with the greatest impact, and also the quantificationof the effect of the factors which can lower β-carotene content. Temperature, occurrence of oxygen, foodcomposition and food structure are shown to affect the β-carotene loss rate significantly. However, the metho-dologies used to obtain the kinetic parameters are of major importance, and finally, most of the results foundin the literature are specific to a study and difficult to generalise. Discussion and conclusion. Mechanisticand kinetic approaches each provide interesting data to improve understanding and monitoring of β-caro-tene. The combination of all this data, together with thermodynamic and analytical considerations, permitsthe building of observable reaction schemes which can further be transcribed through mathematical models.By this multidisciplinary approach, scarcely used for the time being, knowledge could be capitalised anduseful tools could be developed to improve β-carotene retention during food processing and storage.France / fruits / vegetables / storage / processing / carotenoids / isomerisation / oxidation /degradation / chemical reactions

La dégradation duβ-carotène au cours de la transformation ou du stockage desfruitsetdes légumes:mécanismesréactionnelsetaspectscinétiques :unerevue.Résumé — Introduction. La diminution significative de la qualité des fruits et légumes au cours de leurtransformation est une préoccupation majeure de l’industrie alimentaire. Les micronutriments sont particu-lièrement affectés, et, parmi eux, le β-carotène qui présente d’intéressantes propriétés sensorielles, nutri-tionnelles et biologiques. La littérature traitant de la dégradation du β-carotène est très dense, mais la naturedes conclusions diffère en fonction de l’approche biologique, chimique ou technologique du problème.Notre article propose une synthèse de points de vue complémentaires dans l’étude du β-carotène pendantla transformation et le stockage des aliments. Réactions de dégradation. Les principaux composés dedégradation du β-carotène identifiés sont les isomères, les époxides, les apocaroténones, les apocaroténalset les produits de clivage à courte chaîne, dont des composés d’arômes. Un schéma réactionnel détaillé desréactions d’isomérisation et d’auto-oxydation du β-carotène a pu être déduit des données de la littérature.Les voies principales sont bien documentées, mais le schéma réactionnel global reste incomplet. De plus,la plupart des études mécanistiques sont menées en système modèle, donc les données peuvent mal repré-senter le comportement du β-carotène dans des aliments réels. Cinétiques pendant les procédés et lestockage. La détermination des cinétiques de dégradation permet l’identification des réactions les plusrapides, c’est-à-dire généralement celles qui ont les impacts les plus forts, ainsi que la quantification de l’effetdes facteurs qui peuvent diminuer la teneur en β-carotène. La température, la présence d’oxygène, la com-position et la structure affectent significativement la vitesse de perte en β-carotène. Cependant, les métho-dologies employées pour obtenir les paramètres cinétiques sont d’importance majeure et, finalement, laplupart des résultats trouvés dans la littérature sont spécifiques d’une étude et difficilement généralisables.Discussion and conclusion. Les approches mécanistiques et cinétiques fournissent chacune des donnéesintéressantes pour améliorer la compréhension et le suivi du β-carotène. La combinaison de l’ensemble deces données, avec aussi des considérations thermodynamiques et analytiques, permet de construire des sché-mas réactionnels observables qui peuvent ensuite être transcrits en modèles mathématiques. Par cetteapproche multidisciplinaire, rarement utilisée actuellement, les connaissances pourraient être capitaliséeset des outils utiles pourraient être développés pour améliorer la rétention du β-carotène pendant les trans-formations alimentaires et le stockage.France / fruits / légume / stockage / traitement / caroténoïde / isomérisation / oxydation /dégradation / réaction chimique

Cirad-Persyst, UMR 95Qualisud, TA B-95 / 16,73 rue Jean-François Breton,F-34398 Montpellier,France

nawel.achir@cirad.fr

Fruits, vol. 66 (6) 417

ces and available at http://www.fruits-journal.org or http://dx.doi.org/10.1051/fruits/2011058

418

C. Pénicaud et al.

1. Introduction

Carotenoids are among the most importantpigments in fruits [1]. These tetraterpenessynthesised by plants are secondary metab-olites essential for photosynthesis and toprevent photo-oxidation induced by lightintensities. These functions are a conse-quence of the light-absorbing properties oftheir polyene chromophore. Carotenoidsconsist of two classes of molecules: (i) thecarotenes, which are strictly hydrocarbons,and (ii) the xanthophylls, or oxycaroten-oids, which contain one or more oxygenfunctions [2]. β-carotene, which belongs tothe first class, is the most widespread infoods. β-carotene is encountered at highconcentrations in many fruits and vegeta-bles such as carrot, spinach, sweet potatoes,plantain (Musa spp.), apricot, orange, etc.[3]. One of the richest fruits is palm fruit, witha concentration of 200 mg β-carotene·kg–1

(table I).

β-carotene’s chemical formula is C40H56.It is composed of eight isoprenic units withspecific end groups or two β-ionone rings(figure 1). β-carotene is lipophilic, insolublein water and soluble in organic solventssuch as petroleum ether, hexane, etc. Itsphysical, chemical and biological propertiesare mainly derived from its large sequenceof conjugated double bonds. Firstly, the sin-

gle and double bond alternation causes thedelocalisation of the π electrons and makespossible the absorption of light within therange of the visible spectrum. β-caroteneabsorbs blue and purple light with a maximaat 450 nm and therefore has a strong red-orange colour [4]. These chromophoreproperties were initially used for its isola-tion, characterisation and quantification onthe laboratory or the industrial scale [5].β-carotene is also currently used as a foodadditive belonging to the colouring family,with the European denomination E 160; itis increasingly employed because of the ten-dency in the food industry to replace syn-thetic colouring agents with natural ones.This additive can be produced by palm oilconcentration or extraction of paprika ole-oresin [6, 7]. β-carotene is thus an importantcomponent of the organoleptic quality offood, not only because of its colour, but alsodue to its precursor role of aroma com-pounds such as norisoprene and monoter-pene during fruit ripening [1].

The role of carotenoids in human nutri-tion is not based upon the light-absorbingproperties of these molecules but on thenutritional activity as provitamin A [8].Along with α-carotene and β-cryptoxan-thin, β-carotene is a vitamin A precursor,because of its perfect structure of vitamin Adimers. Therefore, it is stoichiometrically

Table I.Composition of some β-carotene-rich fruits and vegetables.

Fruit β-carotene content(mg·kg–1)

β-carotene of total carotenoids(%)

Reference

Apricot 11 84 USDAa

Carrot 65–83 67–70 USDAa [92]

Lettuce 10–14 47 [90]

Orange 0.1–1.4 1–9 [95, 96]

Orange sweet potato 85–93 90–100 USDAa [17, 90]

Palm fruit 200 54 [76, 93]

Plantain 4–10 44 [95]

Pumpkin 12–31 55 USDAa [5, 91]

Spinach 9–19 30 [90]

a USDA, Nutrient Database for Standard Reference, http://www.nal.usda.gov/fnic/foodcomp/search/

Fruits, vol. 66 (6)

Degradation of β-carotene during processing or storage

equivalent to two molecules of retinol [4,9]. The enzyme, β-carotene 15,15’ monoox-ygenase, present in the human intestinalcells and liver, acts on the 15,15’ bond, thusforming two equivalent-retinol moleculesfrom one molecule of β-carotene by centralcleavage [10]. β-carotene is the main impor-tant source of vitamin A, particularly indeveloping countries. This molecule also

has the ability to be an efficient antioxidantbecause of its highly delocalised electronswhich can stabilise by resonance reactiveintermediates such as carbocations or radi-cals. β-carotene can thus protect cellular tis-sues by quenching singlet oxygen andscavenging active free radicals that areinvolved in potentially lethal processes,such as lipid peroxidation [2, 11–13].

FTis9

Fruits, vol. 66 (6

igure 1.rans-β-carotene and its mainomers: 15-cis-, 13-cis- and-cis-β-carotene.

) 419

420

C. Pénicaud et al.

Because of this antioxidant activity, β-caro-tene is often used in food complements orfor pharmaceutical applications. On thefood scale, because of its lipophilic proper-ties, β-carotene can be used in oils where itcan protect unsaturated lipids against per-oxidation [14].

β-carotene, by its structure, exhibits veryinteresting sensory, nutritional and biologi-cal properties. However, its significantnumber of double bonds makes it very sen-sitive to degradation and particularly tooxidation. Indeed, while β-carotene concen-tration increases during fruit ripening [15],its concentration stagnates or decreases dur-ing post-harvest storage at rates varying asa function of the temperature [16]. However,the main critical step for β-carotene lossremains during fruit processing, i.e., juice orpuree production. Indeed, the loss of tissueintegrity, contact with oxygen and light, andthe elevation of temperature during thermaltreatment dramatically increase the rates ofdegradation reactions [4, 17].

The main degradation products identifiedafter food processing are isomers, oxidationand cleavage products [18, 19]. These com-pounds may lower the sensory and nutri-tional properties of the resulting foodproducts. For instance, it was demonstratedthat the cis-isomers of β-carotene havelower antioxidant properties than trans-β-carotene [3] and generate about two-foldless vitamin A [20]. In addition, some studiesreported the increase in oxidative stresscaused by end products of carotene β-oxi-dation [21]. These results show how a foodprocess can be damaging and the importantissue is to control conditions such as tem-perature, light or oxygenation in order toimprove β-carotene retention in processedfood.

The aim of our paper is to present a lit-erature synthesis about the theory ofβ-carotene degradation and its applicationduring food processing and storage. The lit-erature concerning β-carotene degradationis extensive, and the approaches are verydifferent as a function of the biological,chemical and food transformation points ofview. Biological and chemical studies focuson the degradation mechanisms, whilefood-processing work is more devoted to

degradation kinetics in order to optimiseprocess design. Although these approachesare complementary to improve β-caroteneretention during food transformations, dataare actually dispersed and they need to begathered. The first part of this review willdeal with the current knowledge about thechemistry of the β-carotene degradationmechanisms. The second part will be dedi-cated to the study of reaction kinetics, andespecially the different approaches to mon-itoring kinetics in food processes and theeffects of storage or process conditions.Finally, the conclusion will evidence theimportance of both approaches to improvethe comprehension and the prediction ofβ-carotene degradation to further prevent itduring food processing.

2. Degradation reactions

β-carotene is a very reactive compound dueto its highly unsaturated structure, whichrenders it electronically rich by delocalisa-tion of π-electrons. Consequently, it is alsoprone to degradation and more precisely toisomerisation, especially at high tempera-ture, and oxidation, due to the occurrenceof oxygen in food [4]. Molecular oxygen isa diradical, so it cannot react directly withfood components, except if the food com-pounds become radical compounds or ifactive forms of oxygen are produced. Mordishowed that the products of β-carotene oxi-dation by molecular oxygen are similar tothe products obtained in the singlet oxygenoxidation (one active oxygen specie) [22].The involvement of radical species wouldexplain the similarity in product formationin the two reactions. Current thinking is thatthe whole process involves first isomerisa-tion of the all-trans to the cis-isomer,followed by the formation of a diradical, orthey may both occur simultaneously andreversibly (figure 2). The involvementof cis/trans isomerisation in β-carotene oxi-dation was more recently noted byMohamed et al., who showed that the lowestenergy configuration may occur from oxi-dative attack of 9-cis-β-carotene and then 13-cis-β-carotene, before trans-β-carotene [9].These findings show that isomerisation and

Fruits, vol. 66 (6)

Degradation of β-carotene during processing or storage

oxidation are closely linked and must gen-erally be studied together.

2.1. Isomerisation

Trans-β-carotene is predominant in nature[23]. However, significant amounts of the cisforms can be found in processed foods. Cisisomers present one or two configurationchanges at the level of one or many doublebonds (figure 1). These molecules have thesame molecular weight as trans-β-carotene.Separation by HPLC was, however, madepossible by the recent use of the stationaryphase (C30) which provides a good separa-tion of cis isomers [6, 24]. The cis isomersare identified on the basis of their spectralproperties. Indeed, in comparison with thetrans-β-carotene spectrum, their maximalabsorption wavelength is decreased andthey have an absorption band, called the‘‘cis’’ peak, at a characteristic position about142 nm below the longest-wavelengthabsorption maximum [19, 25]. Cis isomeri-sation mainly takes place because of heat.As a consequence, many studies havereported the decrease in trans-β-caroteneand the concomitant increase in cis isomers

in vegetables rich in β-carotene because ofthermal processes such as blanching, pas-teurisation, sterilisation and air drying [18,26]. Light can also favour β-carotene isom-erisation but to a smaller extent in compar-ison with the temperature effect. Forinstance, in the experiments of Chen andHuang, isomerisation of β-carotene in hex-ane reached the same level in 40 min at70 °C in the dark and in 12 hours at –5 °Cunder 2000 lux [27]. Theoretically, depend-ing on the number of double bonds, a mul-titude of mono- and poly-cis isomers can beformed from a given carotenoid. However,in the case of β-carotene, the major cis formsof β-carotene found after thermal process-ing were 15-15’-di-cis-β-carotene, 13-cis-β-carotene and 9-cis-β-carotene, but with amore significant amount of 13-cis-β-caro-tene [18, 26, 28–31]. A molecular modellingstudy of Mohamed et al. showed that trans-β-carotene configuration was the lowestenergy structure but, among cis isomers, thelowest energy configurations were 9-cis-and 13-cis-β-carotene [9]. This more signifi-cant stability may explain why both cis iso-mers are found in high amounts inprocessed food. Based on the apparition

Δ

FFoispap

Fruits, vol. 66 (6

igure 2.irst steps of β-carotenexidation including firstlyomerisation, secondlyroduction of radical species,nd then apparition of cleavageroducts [22].

) 421

422

C. Pénicaud et al.

order of compounds, which can give an ideaof the succession of intermediary products,Marx et al. also stated that, among the cisisomers, the 13- and 15-15’-di-cis-β-carotenewere predominant at low temperature,while 9-cis-β-carotene was formed undermore severe conditions [26]. The amount ofthe different isomers formed is thus verydependent on the thermal conditions butalso on the solvent and the state of β-caro-tene (see section 3.).

2.2. Oxidation

In comparison with isomerisation reactions,the resulting products of oxidative reactionsare much more numerous and different interms of molecular weight, chemical func-tions, etc. β-carotene can be oxidisedaccording to three pathways. Indeed, oxi-dation of β-carotene can be either autoacti-vated (autoxidation), or induced by light(photo-oxidation) or catalysed by enzymes(enzymatic oxidation). Enzymatic oxidationcan occur in fruits essentially because oflipoxigenases. However, bleaching caninactivate these enzymes. For instance,Dutta et al. observed higher β-caroteneretention in bleached pumpkin than in freshpumpkin puree due to enzyme inactivationby heat [5]. Also, during the storage of dehy-drated carrot slices, Koca et al. found lowerdecoloration rates for blanched thanunblanched products [32] (table II). Regard-ing photo-oxidation, Chen and Huang com-pared the effects of temperature and light onβ-carotene degradation and found a kineticconstant increased by a factor 24 duringoven heating at 150 °C compared with illu-mination of 2000 lux at –5 °C, proving thatthe effect of light was negligible comparedwith that of temperature [27]. Also, Rod-riguez and Rodriguez-Amaya did not find amajor impact of light exposure on β-caro-tene degradation in the time scale chosen(21 days) [19]. In addition, photo-oxidationcan be easily avoided during a process bypreventing light around the product, andalso by dark packaging during storage.Finally, autoxidation is the most difficultphenomenon to prevent during foodprocessing and storage and some authors

have attempted to improve knowledgeabout the reaction scheme.

As suggested in the detailed reactionscheme deduced from the literature (fig-ure 3), it is supposed that isomerisationcould be the first step of oxidation, leadingto a diradical of β-carotene which can easilybe attacked by oxygen on either side of thecis bond. This radical attack followed byhomolytic internal substitution gives theepoxides, which appear as initial products.The stable final products, the apocaroten-ones and apocarotenals, could be formedfrom the epoxides.

2.2.1. The initial oxidation products:the epoxides

The oxygen can attack the β-carotene mol-ecule either on the β-ring or on the chain.The homolytic hydrogen extraction couldbe easier at the level of the β-ring. Indeed,the molecular modelling study of Mohamedet al. showed that this position was prefer-ably attacked by oxygen species because ofits long lifetime and low energy [9]. Thiscomputational study also showed that theoxygen attack could be preferentially doneon the trans-isomer, the more stable formof β-carotene. To identify the resulting prod-ucts of epoxidation, Rodriguez andRodriguez-Amaya carried out a controlledoxidation of β-carotene in a model systemwith chloroperbenzoic acid in ambient con-ditions, in the presence and absence of light[19]. They identified β-carotene-5,6-epox-ide, β-carotene-5,8-epoxide, β-carotene-5,6,5’,6’-diepoxide, β-carotene-5,6,5’,8’-die-poxide and β-carotene-5,8,5’,8’-diepoxide.The 5,8-epoxide groups are also known asfuranoid groups. The supposed relationshipbetween these different epoxides and die-poxides is presented in figure 4. At the levelof real food, analysis of carotenoid degra-dation products during thermal processingof citrus juice (75 °C–100 °C) confirmed thatthe isomerisation of the epoxide function inposition 5,6 into a furanoxide function inposition 5,8 was a common reaction for sev-eral xanthophylls [33]. Organic acids liber-ated during the processing of fruit juices arestrong enough to promote rearrangementsof 5,6-epoxide groups into furanoid groups.To the contrary, no evidence was found on

Fruits, vol. 66 (6)

Degradation of β-carotene during processing or storage

Fruits, vol. 66 (6

Tab

leII.

Kin

etic

valu

esof

β-ca

rote

ned

egra

dat

ion

for

diff

eren

tp

rod

ucts

and

pro

cess

esac

cord

ing

toth

elit

erat

ure.

Pro

duc

t[β

-car

oten

e]d

eter

min

atio

nP

roce

ssP

roce

sste

mp

erat

ure

rang

e(°

C)

Kin

etic

dat

aR

efer

ence

k(m

in–1

)E

a(k

J·m

ol–1

)D

(min

)z (°C

)

Sw

eet

pot

ato

chip

str

ans-β-

caro

tene

(HP

LC)

Sto

rage

10–4

02

×10

–6

–2.7

×10

–564

.21.

1×

106

–8.2

×10

423

[17]

Deh

ydra

ted

carr

otsl

ice

Tota

lcar

oten

oid

s(a

bso

rban

ceat

450

nm)

Sto

rage

afte

rb

lanc

hing

27–5

72.

7×

10–6

–3.6

×10

–566

8.3

×10

5

–6.4

×10

425

[32]

Sto

rage

with

out

bla

nchi

ng27

–57

1.5

×10

–5

–5.9

×10

–539

1.5

×10

5

–3.9

×10

443

[32]

Sto

rage

with

out

bla

nchi

ng50

–80

–32

–60

[97]

Ora

nge

juic

etr

ans-β-

caro

tene

(HP

LC)

Mic

row

ave

heat

ing

70–8

50.

02–0

.65

188

100

–3.

511

[49]

Col

our

Ohm

iche

atin

g50

–90

0.02

–0.5

779

125

–4

25[5

3]

Infr

ared

heat

ing

50–9

00.

07–0

.61

5332

–4

37[5

3]

Mic

row

ave

heat

ing

100–

125

0.58

–0.7

814

4–

317

9[5

3]

Car

rot

juic

e–

Hea

ttr

eatm

ent

104–

132

––

–25

[98]

Citr

usju

ice

tran

s-β-

caro

tene

(HP

LC)

Ther

mal

trea

tmen

t75

–100

0.00

2–0

.01

110

1300

–85

20[3

3]

Pum

pki

np

urée

Tota

lcar

oten

oid

s(a

bso

rban

ceat

450

nm)

Ther

mal

trea

tmen

t60

–100

0.00

4–0

.008

2757

5–

287

77[5

]

Pap

aya

pur

éeTo

talc

arot

enoi

ds

(ab

sorb

ance

at45

0nm

)Th

erm

altr

eatm

ent

70–1

050.

002

–0.0

0621

1150

–384

104

[99]

Frie

dp

lant

ain

tran

s-β-

caro

tene

(HP

LC)

Dee

p-f

atfr

ying

120–

180

–87

–34

[48]

Saf

flow

erse

edoi

ltr

ans-β-

caro

tene

(HP

LC)

Ther

mal

trea

tmen

t75

–95

–11

0–

20[1

00]

Oil

tran

s-β-

caro

tene

(HP

LC)

Ther

mal

trea

tmen

t12

0–18

0–

88–

34[4

7]

) 423

424

C. Pénicaud et al.

the ability of β-carotene to form furanoiddirectly without going through the 5,6-epoxide intermediate.

If the attack of the oxygen molecule isdone on the polyene chain of β-carotene, in-chain epoxides are formed. In this case,oxygen attack is preferentially done on cisisomers (figure 2), due to the higher avail-ability of the π-electrons in these cis config-urations. The in-chain epoxides have beenidentified as precursors of cleavage prod-ucts [34], namely the apocarotenones andthe apocarotenals.

2.2.2. Apocarotenonesand apocarotenals

Cleavage can occur (i) from a chain epoxidewhich can be formed directly from a cis iso-mer, or (ii) from a second oxygen attack on

a 5,6-epoxide or furanoid compound, inwhich case the cleavage products are namedepoxy-β-apocarotenals and epoxy-β-apoc-arotenones (figure 3). The complete rangeof β-apocarotenals and β-apocarotenones aswell as diapocarotene-dials that canpossiblybe formed from trans-β-carotene have beendetected during an experiment of mild oxi-dative cleavage by dioxygen induced by aruthenium tetramesitylporphyrin catalyst[34]. All these cleavageproducts arepresentedin figure 4. In the experiments of Rodriguezand Rodriguez-Amaya, epoxidation with m-chloroperbenzoic acid and oxidative cleav-age with potassium permanganate led toproducts identified as β-apo-8’-carotenal,β-apo-10’-carotenal,β-apo-12’-carotenal,β-apo-14’-carotenal and β-apo-15-carotenal, alongwith semi-β-carotenone and monohydroxy-β-carotene-5,8-epoxide [19]. These products

5,6-epoxi-β-ionone

Figure 3.General overview of thedegradation scheme ofβ-carotene.

Fruits, vol. 66 (6)

Degradation of β-carotene during processing or storage

were detected in model systems and someof these products were also found in mangojuice, acerola juice and dried apricot.Increased cis isomerisation was alsoobserved and cis isomers of the oxidationproducts were detected.

2.2.3. Short-chain cleavage products

Some authors concentrated their work onshort-chain cleavage products (maximum of9 atoms of carbon) and mostly on noriso-prenoids, known as flavour compounds.These compounds are issued from β-caro-tene, apocarotenones or apocarotenalcleavage. Most of the works aimed at char-acterising the products formed by degrada-tion of β-carotene. For instance, in oakwood, β-ionone, 5,6-epoxy-β-ionone anddihydroactinidiolide were identified [35]. Inbiological tissues, Sommerburg et al. iden-tified 5,6-epoxy-β-ionone, ionene, β-cyclo-citral, β-ionone, dihydroactinidiolide and

4-oxo-β-ionone as cleavage products formedafter degradation of β-carotene mediated byhypochlorous acid [36]. Non-enzymaticcleavage of carotenoids was supposed to becarried out primarily by oxidants liberatedby polymorphonuclear leukocytes.

From a mechanistic point of view, onlythe dihydroactinidiolide was submitted toinvestigations on its formation pathways,and at least two reaction pathways could beevidenced (figure 3). Bosser and Belindescribed a system able to generate free rad-icals to cleave β-carotene, giving rise toβ-ionone, 5,6-epoxy-β-ionone and dihy-droactinidiolide [37]. Under these conditions,in another study and at 37 °C, two main reac-tion pathways could be put forward [38]: onewould involve a free radical oxidising mech-anism, leading to β-ionone, then to 5,6-epoxy-β-ionone, and then to dihydroacti-nidiolide. This way links the 5,6-epoxy-β-ionone to its precursor β-ionone. The

FD[1βd

Fruits, vol. 66 (6

carotenone

in chain epoxides

igure 4.etailed formation of epoxides9] and β-apocarotenals and

-apocarotenones [34] from theegradation of β-carotene.

) 425

426

C. Pénicaud et al.

second would involve a thermal process,leading from the 5,6-epoxy-β-ionone to thedihydroactinidiolide exclusively, at 37 °C.Free radicals and variation in pH value didnot modify in a significant manner the yieldor the kinetics of this reaction. From a moretheoretical point of view, according to pre-dictions from calculations of minimal freeenergies of oxidation [39], for β-carotene, thefavoured cleavage would be β-cyclocitral(C7) and β-apo-8’-carotenal (C8’) whereasfor the 9-cis-isomer, the favoured cleavagebond would be the cis bond (9-10), givingrise to β-ionone (C9) and β-apo-10’-carote-nal (C10’). Experimentally, Wache et al.showed that higher ratios of 9-cis-β-caroteneincreased the formation of dihydroactinidi-olide [39]. However, the authors were notsure whether the 9-10 cleavage site wasfavoured, as proposed by the prediction, orif the 9-cis-isomer was first transformed intoits epoxide and then cleaved at the 8-9 level.All these studies support the idea that at leasttwo ways can be followed to produce dihy-droactinidiolide, as shown in figure 3.

2.2.4. Unclear reaction pathways

Whilst this general degradation scheme (fig-ure 3) is supported by the findings of Mordiet al. [40], some other compounds were alsofound. Epoxides, dihydrofurans and carbo-nyl compounds, but also carbon dioxide,oligomeric material, traces of alcohols, andprobably carboxylic acids were formed. Themain products in the early stage of the oxi-dation were shown to be 5,6-epoxy-β-caro-tene, 15,15’-epoxy-β-carotene, diepoxides,and a series of β-apo-carotenals and β-car-otenones. As the oxidation proceeded,uncharacterised oligomeric material and thecarbonyl compounds became more signifi-cant while the epoxides degraded. In thefinal phase of the oxidation, the longer-chain β-apo-carotenals were themselvesoxidised to shorter-chain carbonyl com-pounds, particularly β-apo-13-carotenone,β-ionone, 5,6-epoxy-β-ionone, dihydroacti-nidiolide and probably carboxylic acids.The oxidation of β-apo-8’-carotenal and ret-inal under similar conditions was studiedbriefly, and the main products from theformer compound were characterised.

Some compounds identified in the liter-ature are not in figure 3 because their modeof apparition/degradation remains unclear:dioxetanes [22], monohydroxy-β-carotene-5,8-epoxide [19], ionene and 4-oxo-β-ionone [36], dihydrofurans, carbon dioxide,uncharacterised oligomeric material, tracesof alcohols and supposed carboxylic acid[40], and polymers of β-carotene [41]observed together with degradation whenβ-carotene was heated and exposed to air.

As all the compounds found as degrada-tion products could not be integrated, fig-ure 3 is necessarily a simplification of thereal reaction scheme. Moreover, this schemedoes not take into account the radical natureof the reactions. Indeed, the initiation, theformation of the epoxides, the β-apo-caro-tenals and β-carotenones, the successivechain shortening of the aldehydes to theketones, and the formation of dihydroacti-nidiolide have been explained in terms offree radical peroxidation chemistry [40].Epoxide formation has been shown to beaccompanied by the release of an alcoxylradical that may continue the chain oxida-tion [22, 42, 43]. Also, more β-carotene per-oxyl radicals are formed at higher concen-trations of β-carotene. Thus, both epoxideformation and β-carotene peroxyl radicalformation enhance the chain oxidation.

The studies which allowed building thisreaction scheme also have their own limits.In most cases, experiments were carried outin model systems. This is a good way toinvestigate a research area from a theoreticalpoint of view, but does not necessarily fitreality in food, as illustrated by the work ofRodriguez and Rodriguez-Amaya, who didnot find in mango juice, acerola juice anddried apricot all the products detected in themodel systems [19]. The lack of studies inreal food products renders impossible theestablishment of clear correlations betweenfood nature and composition and the pre-ferred reaction pathways. Moreover, massbalances are never complete in studiesabout carotenoids, especially in real foods,due to the very high number of compoundsinvolved in the overall reaction scheme. Itis obviously very hard to fully quantify allcompounds during one experiment, notonly due to the time needed for the analysis

Fruits, vol. 66 (6)

Degradation of β-carotene during processing or storage

itself, but also because some of these com-pounds can stay in the product; so an extrac-tion stage would be necessary beforeanalysis, or can go in the gas phase, whereloss can easily occur between their produc-tion and their quantification. Even though,nowadays, the use of HPLC, mass spectrom-etry and Electron Spin Resonance (ESR)makes the identification and the quantifica-tion of a very significant quantity of degra-dation products possible [44]. However,analytical techniques still have their currentlimits, especially in quantification limit,which may prevent full quantification of allcompounds.

Considering all these difficulties to estab-lish a complete degradation scheme ofβ-carotene, and above all the influence ofthe food’s nature and composition on thereaction pathways, the examination of deg-radation kinetics appears to be completelynecessary in order to i) identify the mostimportant reactions in terms of rate, and ii)quantify the factors which can affect thekinetic values.

3. Kinetics of β-carotenedegradation during fruitprocessing or storage

The level of β-carotene in processed fruitsand vegetables is essential in nutritional andcommercial terms for the industry sincefruits and vegetables are the principalsources of β-carotene and vitamin A precur-sor. The guarantee of a maximal preserva-tion of β-carotene is thus an interestingcommercial argument. But labelling a fruitjuice with a guaranteed content of β-caro-tene after processing and during storagerequires good knowledge of β-carotenedegradation kinetics for the determinationof the optimal shelf life. Indeed, significantlosses occur during processing and storage,and many factors such as time, temperatureor occurrence of oxygen can significantlyaffect β-carotene retention. For instance, inorange sweet potatoes Wu et al. found from8% up to 66% of β-carotene loss by usingdifferent food cooking processes [45]. Thequantified knowledge of the parameters

which impact β-carotene degradation istherefore important for the choice and thedesign of a process or the selection of thebest storage conditions to provide productswith higher nutritional potential.

3.1. Kinetic model for β-caroteneloss

Most of the studies in real food report a one-order reaction with respect to the concen-tration of β-carotene:

[ ] (1),

where is the content ofβ-carotene, k the reaction rate constant, andt the time given in s (SI units), or more fre-quently in min.

Some authors also use the representationusually used for microorganism inactivationkinetics during thermal processes:

[ ] (2),

where D is the decimal reduction time inmin, i.e., the time required to reduce theβ-carotene concentration by 90%. D isrelated to the reaction rate constant byD = [ln(10) / k].

The use of a one-order kinetic is realisticin many cases. From this model, the degra-dation rate constant or decimal reductiontime can be easily calculated. However,some studies tested superior reaction ordersby linearisation methods [46] or non-linearregression [47] and found a better fit ofexperimental data with orders superior thanone for trans-β-carotene degradation innon-polar solvents. This fact may beexplained by the competition with isomer-isation reactions particularly important inthese types of solvents [27].

The concentration of β-carotene can beobtained by HPLC [17, 33, 48, 49]. However,in kinetic studies, the spectrophotometricmethod after extraction is more usuallyemployed because of its lower time andmoney cost [5, 32, 50]. However, this methodmay evaluate not only trans-β-carotene

β carotene–[ ]t

β carotene–[ ]t 0=------------------------------------------------⎝ ⎠

⎛ ⎞ln k t⋅–=

β carotene–[ ]

β carotene–[ ]t

β carotene–[ ]t 0=------------------------------------------------⎝ ⎠

⎛ ⎞log tD----–=

Fruits, vol. 66 (6

) 427

428

C. Pénicaud et al.

concentration but also its cis-isomers andoxidised products which also absorb at450 nm and with different response coeffi-cients than that of trans-β-carotene [4].Lastly, some kinetic studies also propose akinetic evaluation of β-carotene loss fromthe monitoring of a physical property sup-posed to be correlated with β-carotene con-tent, such as colour. This measurement ofβ-carotene content is convenient since itavoids a significant experimental effort.However, the resulting kinetic data are quitemeaningless from a chemical point of viewsince colour may come from other pigmentsand, during thermal processes, other reac-tions such as Maillard reactions are sup-posed to occur at the same time and alsoimpact the product colour. Therefore,before using colour as a representativeproperty for β-carotene loss, a correlationstudy must be done. Lastly, Zepka et al. pro-vided both carotenoid concentrations and acolour parameter to evaluate β-carotenedegradation in a cashew apple juice model[51]. They evaluated and correlated bothresponses via the same kinetic constantrates. The resulting kinetic data provideduseful information for the quality control ofcarotenoids and the related juice nutritionalvalue during the thermal process. Forinstance, it could be calculated thatΔE* = 1.9 (E* being the total colour meas-urement), which is visually perceived, pro-motes a 16% reduction of provitamin Avalue, whereas ΔE* = 3 implies a more rel-evant 36% loss of the provitamin A value.This is obviously a result of interest for thejuice industry, due to the ease of controllingcolour changes in comparison with the time-consuming chemical analysis. This type ofinformation is also available for orange juice[52] and papaya puree [53]. Other authorssuggested that in model systems, the light-ness index (L*) seemed to be a good indi-cator of the decrease in β-caroteneconcentration, while the changes in the red-ness/greenness index (a*) coincided withthe production of the volatile compoundβ-ionone [54].

The majority of the kinetic models usedto describe β-carotene degradation areuniresponse kinetic models represented byequations (1) or (2). However, as detailed

in the previous section, β-carotene is sup-posed to degrade in various products,mainly cis isomers, and oxidised and cleav-age molecules. The real reaction scheme ismuch more complex, reactions are of highdynamics and are therefore hard to monitor.Indeed, the evaluation of kinetic constantsis complicated by the simultaneous appari-tion and disappearance of intermediaryproducts whose lifetimes can be very short,rendering tedious their detection and thustheir quantification over time. To overcomethese difficulties, Zepka et al. proposed asimplified multi-response model accordingto the reaction scheme in figure 5 to repre-sent carotenoid degradation in a modelcashew apple juice [51]. The mechanisminvolves parallel irreversible and reversiblecoupled reactions of both trans-β-cryptox-anthin and trans-β-carotene to yield, respec-tively, degradation compounds and mono-cis-isomers. Therefore, thanks to the globalmonitoring of the two types of products(volatile and non-volatile, respectively),they could have access to the different con-stant rates, discriminate the two pathwaysand even evaluate the temperature effect.

In many food systems, the most impor-tant extensive variable toward the reactionrate is temperature. Therefore, the temper-ature dependency of a reaction is importantand useful information to design and deter-mine time and temperature couples duringcommon processes such as pasteurisation,sterilisation, canning, etc. In the literature,the temperature dependency is often givenby the Arrhenius law, resulting in the calcu-lation of an activation energy:

[ ] (3),

where k is the kinetics constant rate (s–1), k0the Arrhenius pre-exponential factor (s–1)(for a first-order kinetic), Ea the activationenergy (J·mol–1), R the ideal gas constant(8.314 J·K–1·mol–1) and T the absolute tem-perature (K).

The temperature dependency may alsobe given by the Bigelow model:

[ ] (4),

k k0

Ea

RT--------–⎝ ⎠

⎛ ⎞exp=

D1

D2-------⎝ ⎠

⎛ ⎞logT 2 T 1–

z-------------------=

Fruits, vol. 66 (6)

Degradation of β-carotene during processing or storage

where D1 and D2 are the decimal reductiontime for the temperatures T1 and T2, respec-tively, and z is the temperature sensitivity orthermal resistance constant in °C.

Conversion of Ea and z is obtained usingthe following relationship:

[ ] (5).

3.2. Kinetic data for various productsand conditions during storageor processing

The literature gives kinetic data for severaltypes of products, liquid, solid and for dif-ferent process or storage conditions. Thanksto the previous equations 1 to 5, kinetic dataobtained with the D-z and the k-Ea modelswere summarised for several processes andtemperatures (table II).

Firstly, it can be observed that reactionrates k or decimal reduction times D are verydifferent when obtained during storage orduring processing. Indeed, during storage Dvalues can be easily expressed in months[17, 32], while they can be expressed inhours or minutes during processing [49, 53].These large differences are due to the sig-nificant temperature dependency of thedegradation reaction to temperatures.Indeed, storage usually occurs at tempera-tures below 50 °C, which is not the case ofthermal processing whose temperature mayvary from 60 °C, for pasteurisation treat-ments, to 100–120 °C for sterilisation, andeven to 180 °C for deep-fat frying treat-ments. However, temperature is not the onlyfactor influencing kinetic rate constants.Indeed, even for similar products and/orprocess conditions, rate constants can bevery different (table II). For instance, for thesame product and the same drying temper-ature, kinetic data may be different becauseof the use of a blanching step inducingenzyme destruction (see section 2.2.). Moremarkedly, for orange and citrus juices, theD values obtained for conventional heatingare much higher than those obtained formicrowave, ohmic or infrared treatments.This fact may be due to the much more effi-cient heat transfers with these non-conven-

tional heating methods leading to shorterprocessing time but also higher β-carotenedegradation. For instance, Fratianni et al.found a β-carotene degradation of about50% after 1-min microwave heating at 75 °C[49], while Dhuique et al. found the samedegradation after 250 min [33]. The D valuesare even higher for products such as papayaor pumpkin purees, having high viscositiesthat limit the heating.

For each process (table II), the kineticstudy of β-carotene degradation at differenttemperatures enabled the calculation of thereaction temperature sensitivity, expressedin activation energies (Ea) or the thermalresistance constant z. Nine values of calcu-lated activation energies are higher than50 kJ·mol–1, corresponding to z values infe-rior to 34 °C. This can show a peculiar tem-perature sensitivity of β-carotene towards anelevation of temperature, which is not nec-essarily the case for all vitamins. Forinstance, Dhuique-Mayer et al. found acti-vation energy of 35 kJ·mol–1 for vitamin Cdegradation against 110 kJ·mol–1 for β-car-otene in citrus juice [33]. Heat seems to acti-vate nearly all β-carotene degradationpathways. It has been evidenced that heatinduces isomerisation of the all-trans-β-car-otene to the cis forms, which can beexplained by the more elevated electronmobility with temperature increase. Heatalso favours oxidation. Indeed, the forma-tion of a free radical is a reaction presentinga high activation energy (from 146 kJ·mol–1

to 272 kJ·mol–1) so it can be facilitated byhigh temperatures [55].

However, despite this tendency, activa-tion energies (Ea) and thermal resistancevalues (z) are supposed to be independentof products or process conditions. However,values of Ea range between (14 and188) kJ·mol–1 and z values from (11 to179) °C. They exhibit therefore a significantdispersion. Therefore, sensitivity to heat isobviously very dependent on the processand product. Indeed, the β-carotene reac-tion is very dependent on the presence ofco-substrates (see section 3.4.1.) which maybe found in very different concentrations indifferent food matrices. Lastly, a globalmeasure such as colour may include otherreactions. In addition, activation energies

Ea2.03 T min T max R⋅ ⋅ ⋅

z-------------------------------------------------------=

Fruits, vol. 66 (6

) 429

430

C. Pénicaud et al.

found under 100 °C with a significant tem-perature range (50 °C to 90 °C) [33, 53] maybe hard to compare with a process above100 °C with a narrow temperature range(100 °C to 125 °C) [53]. Therefore, activationenergies found in the literature must betaken with precaution. In many cases, theyare calculated empirically and are valuableto design process conditions only for a givenapplication. In addition, they give no furtherinsight into the degradation mechanismand, therefore, no transposition can bemade for other products or processes.

Some studies followed not only β-caro-tene degradation but also degradation prod-uct apparition. Zepka et al. identified thereaction rates according to the reactionscheme of figure 5 at different temperaturesfrom 60 °C to 90 °C in a cashew apple juicemodel [51]. From the values of kinetic con-stant rates they obtained on the basis of bothcarotenoid level and colour parameterchanges (table III), it was clear that k3 waslargely superior to k1 and k2, indicating that

the formation of degradation compoundswas much faster than the isomerisationprocess. From these data, a rough estima-tion of the activation energy Ea,i of each indi-vidual reaction was possible (table III),assuming a linear behaviour of the classicalArrhenius equation between both tempera-tures. The activation energies of the irrevers-ible formation of degradation compounds(reaction 3) and of the cis → trans back-isomerisation reaction (reaction 2) werealmost the same, and are both lower thanthat of the direct formation of the mono-cisisomers (reaction 1). That means that reac-tion 1 is the less favoured one, while reac-tions 2 and 3 are equally favoured.However, the [k3 / k2 ] ≈ 30 indicated thatthe formation of degradation compoundswas a highly entropic process, probably dueto breakdown of the large all-trans mole-cules into shorter-chain derivatives. In addi-tion, the present mechanism allowed thecalculation of the overall activation energyfor the thermal degradation of the main

.

Table III.Values of kinetic parameters obtained for the simplified β-carotene degradationscheme of carotenoids in a model cashew apple juice [51] described in figure 5.

Kinetic parameter Reaction 1C → I

Reaction 2I → C

Reaction 3C → P

k60 °C (s–1) 8.3 ± 2.8 × 10–7 5.8 ± 1.1 × 10–6 15.4 ± 1.1 × 10–5

k90 °C (s–1) 3.1 ± 0.6 × 10–5 6.1 ± 1.4 × 10–5 18.5 ± 2.2 ×10–4

Ea (kJ·mol–1) 114.2 ± 18.8 78.2 ± 10.5 82.8 ± 8.4

Figure 5.Simplified β-carotenedegradation scheme ofcarotenoids in a model cashewapple juice by Zepka et al. [51]

Fruits, vol. 66 (6)

Degradation of β-carotene during processing or storage

all-trans carotenoids in the cashew applejuice model as (Ea,1 − Ea,2) + Ea,3 =118.6 kJ·mol–1, a value comparable with thevalues detailed in table II.

Such an approach is very interesting froma mechanistic point of view, since it suppliesevidence to complete theoretical calcula-tions and studies carried out in model sys-tems. In this study, the authors proposed amodel which tends to refute the idea thatβ-carotene degradation would preferen-tially go through a first step of isomerisation.It would have been of great interest to com-pare their results with those obtained witha model in which the isomers would havebeen the intermediary products betweentrans-carotenoids and cleavage products.This could have been a way to discuss thetwo supposed reaction mechanisms. Whatis certain is that degradation productsincrease with processing time and temper-ature. That is the case for isomers [18, 19,56] and also for oxidative products, althoughthey are more reactive and harder to meas-ure [19].

3.3. Effect of oxygen

The antioxidant activity of β-carotene con-sists either of physical quenching of singletoxygen or scavenging reactive oxygen spe-cies. This antioxidant activity being partof the degradations that β-carotene canundergo, occurrence of oxygen in food canobviously impact the β-carotene degrada-tion rate.

However, at first, the effect of oxygen wasmostly studied from a mechanistic point ofview. In the self-initiated oxidation of β-car-otene with molecular oxygen, the rate ofoxygen uptake was shown to depend on theoxygen partial pressure [40]. Perez-Galvezand Minguez-Mosquera also stated that oxy-gen was the more important limiting factorin carotene degradation in lipid systems [12].Tsuchihashi et al. even proposed reactionpathways for the reaction of β-carotene inlipid systems [43]. Peroxyl radical was sup-posed to add to β-carotene to give a stableβ-carotene radical which may undergo sev-eral competing reactions. It may react withanother radical to give a stable product. It

may react with oxygen to yield a β-caroteneperoxyl radical, which may react withanother radical to give stable products,attack another β-carotene molecule toinduce an autoxidation of β-carotene, orattack a substrate such as lipid to generatelipid radical and induce chain oxidation.The β-carotene radical may also undergoβ-scission to give an epoxide and alkoxylradical, which may continue oxidation. Theeffect of oxygen is thus a major one.

In real food products, most of the studiesconsist of comparisons of carotenoid deg-radation (or retention) level when food issubmitted to different oxygen levels. Forinstance, high oxygen concentrations havebeen associated with high levels of carote-noid degradation during storage in driedsweet potato flakes [57], in pasteurisedmango puree [29] and in semi-preservedtomato sauces [58]. The occurrence of oxy-gen during processing has also been inves-tigated: it was found that low-pressuresuperheated steam drying and vacuum dry-ing led to less degradation of β-carotene incarrot than hot air drying because this lastprocess was the most aerobic [18].

Some authors attempted to define moreprecisely the relationship between oxygenand carotenoid loss and thus related theirdegradation kinetic constant rates to theoxygen level around the sample. Driedsweet potato chips stored at 40 °C andflushed with nitrogen had a degradation rateconstant of 12.4 ± 2.4 × 10–8 s–1, whilstthose flushed with 2.5%, 10% and 21% oxy-gen had respective degradation rate con-stants of 3.51 ± 0.61 × 10–7 s–1, 5.95 ± 0.25 ×10–7 s–1 and 9.87 ± 0.44 × 10–7 s–1 [17]. In oilof gac fruit, a Southeast Asian fruit, the rateof β-carotene degradation was found to be5.0 ± 0.5 × 10–8 s–1 and 1.04 ± 0.17 × 10–7 s–1

at 45 °C and 60 °C, respectively, when sam-ples were flushed with nitrogen, whereasthey were 8.3 ± 0.2 × 10–8 s–1 and 1.57 ± 0.5 ×10–7 s–1 at 45 °C and 60 °C, respectively, incontrols [59]. Decreasing the oxygen level inthe atmosphere around the food unmistak-ably decreases the β-carotene loss rate.

Unfortunately, few data are available con-cerning the quantified impact of dissolvedoxygen on β-carotene degradation rates.The authors who worked on this subject

Fruits, vol. 66 (6

) 431

432

C. Pénicaud et al.

generally carried out their measurements inorganic solvents or oils, taken as model sys-tems for carotenoid degradation because thedegradation pathways were more eluci-dated in lipids than in fruits or vegetables.Some authors experimentally studied andkinetically modelled the autoxidation ofβ-carotene in n-decane as a solvent undervarious conditions of temperature and initialdissolved oxygen content [60]. The kineticmodel was based on a chain reaction mech-anism composed of 7 reactions: 2 initiationreactions, 2 propagation reactions (includ-ing 1 reversible reaction) and 2 terminationreactions. In another study, Takahashi et al.presented a kinetic model of β-carotene oxi-dation in the presence of an antioxidant (α-tocopherol) in n-decane (19 reactionsincluding the co-oxidation of both caroten-oids) under various conditions of tempera-ture and constant oxygen level varying foreach temperature between (20 and40) mol% [61]. The kinetic model proposedtook into account the concentration of allreactants including oxygen and quantita-tively described the oxidation of both β-car-otene and α-tocopherol over a wide rangeof temperatures, oxygen contents and initialantioxidant concentrations.

The same approaches were carried outnot only in n-decane but also in oleic acid.The authors observed that, when oleic acidwas the solvent of the reaction, internal oxy-gen mass transfer from the atmosphere intothe oil had to be taken into account, prob-ably because, in this case, oleic acid alsoconsumed oxygen due to its own oxidation,and thus oxygen transfer was the limitingfactor. Internal oxygen transfer was thusincluded in the proposed kinetic model,which was based on the reaction mecha-nism consisting of the oxidation of β-caro-tene (7 reactions), the oxidation of oleicacid (2 reactions), and the cross-reaction ofβ-carotene with oleic acid (1 reaction), i.e.,a total of 10 reactions [62]. In a last study [63],oxidation experiments with β-carotene werealso performed in oleic acid solvent but withthe addition of α-tocopherol. In this caseagain, internal oxygen transfer was takeninto account. The kinetic model was basedon a reaction mechanism involving 25 reac-tions and simulated well the time over

which β-carotene was almost totally con-sumed under practical storage conditions atroom temperature in air.

Such models can be very powerful toolsto investigate effects of the different param-eters acting on the degradation of thecarotenoids and, conversely, to providequantitative data on the process and storageconditions to carry out in order to minimisecarotenoid loss. However, development ofthese mechanistic models involves theknowledge of the oxygen concentration inthe medium. Besides, the models citedabove were based and validated on exper-imental contents of antioxidants or oxida-tion products, but not on oxygen content.Thus, the influence of oxygen which isobtained from these models can be disput-able. In fact, due to technical limitations, itis hard to obtain data about oxygen concen-trations in oils, and even more difficult infruits since they are solid. Furthermore, inreal food, the measurement of oxygen sol-ubility is complicated by occurrence of oxi-dable compounds which tend to disturbmeasurements. From the literature, it canonly be said that oxygen solubility woulddecrease with an increase in temperatureand dry matter in aqueous products andwould be higher in oils than in aqueousproducts [64–67]. For instance, the oxygencontent in water is 13 mg·L–1 at 4 °C, 9 mg·L–1

at 20 °C and decreases to 0 mg·L–1 at 100 °C,whereas, in oils, it is around 30 mg·L–1 what-ever the temperature in the range of 20 °Cto 50 °C. In the case of solid foods, oxygentransfer is limiting because of the low oxy-gen diffusion coefficients from the atmos-phere into the food [68]. However, theknowledge of the diffusion coefficient of theoxygen in the food is a parameter very hardto achieve experimentally. Despite manyimprovements during the last century, oxy-gen quantification remains nowadays themain bottleneck to enlarging knowledge onthe oxygen impact on food products [2, 69].Some recent oxygen probes (optical fibre ofabout 100 µm in diameter, for example),based on luminescence quenching by theoxygen, should help researchers to investi-gate this area since these sensors present theadvantages of consuming no oxygen and

Fruits, vol. 66 (6)

Degradation of β-carotene during processing or storage

allowing high spatial resolution in all mate-rials [68–70].

3.4. Effect of food matrix

Because of the diversity of fruits and vege-tables and the complexity of their composi-tion, the effect of the food matrix onβ-carotene degradation is very difficult tounderstand. Two major factors can be evi-denced: the composition in itself, and thestructure of β-carotene in the food, which isdependent on the type and structure of theproduct: liquid, solid, emulsion, etc.

3.4.1. Effect of food composition

Composition is very different among thevarious vegetables and fruits according tothe different genre, species and variety.Even in the same variety, composition var-iations may occur because of the climaticconditions. Moreover, sometimes, in thesame fruit, composition difference mayoccur as a function of its different parts.Therefore, kinetic studies are very hard toconduct on real products, explaining whysome authors have attempted to elucidatesome kinetic parameters on model food.

– Water: It has been evidenced that thelower the water activity, the faster the β-car-otene degradation. During isothermal stor-age at 40 °C under air of dried sweet potatochips, water activity (aw = 0.13–0.76) had asignificant impact on carotenoid degrada-tion, with rate constants varying between5.71 × 10–7 s–1 and 3.95 × 10–7 s–1, respec-tively [17]. Previous research on freeze-driedsweet potato cubes also showed higher lev-els of β-carotene degradation at lower wateractivities [71].

– Acid: The effect of acid on carotenoiddegradation has been reported in a fewstudies. Mortensen et al. studied degrada-tion of carotenoids with nitric acid and mod-erately strong acids, such as trichloroaceticand trifluoroacetic acids [72]. The interme-diary reactions were mono- and di-proto-nated carotenoids, which exhibited a longlifetime (hours) in the experimental condi-tions of the study. It has also been shownthat organic acids liberated during theprocessing of fruit juices are strong enough

to promote rearrangements of 5,6-epoxidegroups into 5,8-furanoid groups of caroten-oids [33, 73].

– Lipid unsaturation: Liu and Chen studiedβ-carotene degradation in an oil model at60 °C and 120 °C [56]. Higher degradationrates were found in saturated fatty acids thanin unsaturated fatty acids. They stated thatunsaturated lipids were prone to reactingwith oxygen and therefore could enter intocompetition with β-carotene. However, onthe contrary, Goulson and Warthesen [74]and Budowski and Brondi [75] observed thatcarotene degradation increased as thedegree of oil unsaturation increased. Theyconsidered that this higher rate was due tothe faster oxidation of unsaturated lipidsproducing radicals likely to attack caro-tenes. Lastly, Perez-Galvez and Minguez-Mosquera evidenced that carotenoids couldreact with oxidative products of lipids butdid not find any differences in carotene deg-radation in different fatty acid substrates[76]. The influence of lipid unsaturation isthus unclear.

– Antioxidants: Many biological studiesreport interactions of carotenoids with otherantioxidants, and particularly with vitamin Eand C. Vitamin E is a generic name gatheringeight tocochromanols (four tocopherols andfour tocotrienols). Tocochromanols are alsolipophilic and can be encountered in oilscontaining β-carotene such as palm oils [77].These molecules proved to have a betterchain-breaking action than β-carotene, par-ticularly in free-radical-induced peroxida-tion [11]. Besides, some works report a pro-tective role of tocochromanols, particularlyα- and γ-tocopherol, against β-caroteneautoxidation [78]. This protective role hasbeen shown in lipid models such as purifiedtriacyl glycerol fraction [79] or in oleic acid[61, 63]. Some degradation studies in oil sys-tems even showed that carotenes and toco-chromanols had synergistic effects in theirprotective effects. Indeed, in a membranemodel, a combination of β-carotene andα-tocopherol inhibited lipid peroxidationgreater than the sum of the individual inhi-bitions [80]. In vitro, interactions were alsodemonstrated by Packer between β-caro-tene and ascorbic acid (vitamin C) in low-density proteins [81]. Ascorbic acid was

Fruits, vol. 66 (6

) 433

434

C. Pénicaud et al.

proven to act synergistically with β-caroteneto prevent oxidation and β-carotene loss.However, as ascorbic acid is hydrosoluble,interactions with β-carotene are possibleonly in particular amphiphilic structures,such as cellular membranes or emulsions.

– Metals: Contrary to antioxidants, metalshave an oxidant role. Polyakov et al. statedthat β-carotene offers little protectionagainst metal-induced lipid peroxidation[82]. Indeed, as unsaturated lipids, caroten-oids can be oxidised by transition metalespecially at low pH [83]. Metals studied insuch reactions are iron [83] and copper [78].

3.4.2. Effect of structure

During processing, micronutrients in fruitsor vegetables are firstly degraded becauseof the first steps of tissue breakdown duringcutting, blending or crushing. Oxidativereactions occur as a result of the contact withambient air but degradations may also occurbecause of the disorganisation of initial cel-lular structures and solubilisation in othersolvents. In plants, carotenoids are locatedin the chromoplasts. Microscopic studiesreveal that within the chromoplast, β-caro-tene can be either in a crystalline form orpartially solubilised in lipid droplets as afunction of the vegetable [29, 84]. Forinstance, it has been shown that, in mango,β-carotene was preferentially solubilised inlipid droplets and also that a large portionof cis-β-carotene naturally occurs [85]whereas, in carrot, it is mostly present incrystalline form and the all-trans isomer pre-dominates [26]. Furthermore, the addition ofgrape oil to carrot juice before heat treat-ment enhanced the 13-cis-β-carotene forma-tion (18.8%) as compared with the control(6%) [26]. This fact was attributed to the par-tial dissolution of crystalline carotene,present in the intact carrot in lipid droplets,indicating that the solubilisation of caro-tenes was a prerequisite for the formationof cis-isomers. It was also noted that thereverse reaction, isomerisation of cis- totrans-isomer, occurred in partly melted solidβ-carotene when β-carotene was heated at90 °C and 140 °C [41]. Chen and Huangadded that the level of isomerisation ofβ-carotene was dependent on the solvent

and that higher levels were reached in non-polar solvents [27].

The solvent in which carotenoids are sol-ubilised may also have an effect on their glo-bal degradation. Indeed, in polar solventssuch as water, the oxycarotenoids proved todegrade much faster than the carotenes [33].On the contrary, in organic solution, Ola-tunde Farombi and Britton found initial ratesof oxidation superior for β-carotene than forlutein, an oxycarotenoid [86]. They sug-gested that lutein, with its hydroxyl group,was more polar than β-carotene and maypossibly react less in a non-polar solvent.

The protective effect of the food structureon β-carotene has been particularly investi-gated in tomato products during heat treat-ments [87]. The main results showed thatβ-carotene was more sensitive to isomerisa-tion than lycopene. Indeed, the heat treat-ment imparted changes or deformation ofthe physical ultrastructure of the cell walland organelles, and β-carotene with its twobulky β-ionone rings could hardly reorgan-ise and bear these changes as lycopene did.Similar results were obtained during hot-break processing of tomato juice and evenof tomato paste; the amounts of trans- andcis- lycopene isomers remained almostunchanged, whereas increased levels of cis-β-carotene were found [88]. These differentstudies evidenced that the nature of thestructure where carotenoids are depositedand the physical state of the pigments arecrucial for the stability of the all-trans con-figuration.

4. Discussion and conclusion

Industrial food processing is often incrimi-nated in lowering the nutritional value ofproducts. Therefore, there is an increasingdemand to understand and prevent the deg-radation of nutrients during processing andstorage.

The first approach consists of the estab-lishment of reaction pathways which canlead to nutrient losses. In the case of β-car-otene, it has been shown that both isomer-isation and oxidation could decrease thecontent of this vitamin, corresponding to

Fruits, vol. 66 (6)

Degradation of β-carotene during processing or storage

about thirty identified degradation productsand at least as many reactions only in thecase of autoxidation. Still, not all autoxida-tion reactions have been fully elucidated.That means that if enzymatic oxidation, pho-toxidation and eventually co-oxidation withlipid substrates or other antioxidants hadbeen considered, hundreds of reactionscould have been found. Yet, all these deg-radation pathways could potentially occurin a real food product.

Under these conditions, the secondapproach, the kinetic one, seems obvious.Among all the possible degradation path-ways, which ones are the fastest and thuswhich ones will predominate for a givenproduct submitted to a known process orstorage conditions? Concomitantly, thedevelopment of analysis automation tech-niques encourages researchers to sophisti-cate kinetics monitoring of degradationreactions during processing. Therefore, dif-ferent studies report kinetic parameters suchas reaction order, rate constant and activa-tion energies for particular degradation mol-ecules such as cis isomers. As extensivelydetailed in our review, some evidence canbe pointed out on the basis of kinetic anal-ysis. For instance, it is clear that β-carotenedegradation increases with processing timeand temperature, and for all degradationpathways. Furthermore, Arrhenius andBigelow models are adequate to describethe influence of the temperature on kineticrates. It can also be said that the environ-mental level of oxygen significantly impactsβ-carotene degradation: the more oxygen,the faster the degradation for both process-ing and storage. On the contrary, the lowerthe water activity of the food, the faster theβ-carotene degradation. It has also beenshown that the occurrence of antioxidantssuch as tocopherols (vitamin E) or ascorbicacid (vitamin C) could lower the β-carotenedegradation rate, whilst metals such as ironor copper could increase it. In most of thekinetic studies, one-order kinetics is usedand is generally realistic. However, themajority of studies exhibit only a global andunique degradation response such as colourloss, which hides the mechanism and dis-simulates the degree of freedom in the con-trol of reactions. These studies allow

drawing general trends, among them theones cited above, but the quantified impactof each parameter is still difficult to obtain.The drawback is that knowledge cannot becapitalised. Therefore, the data are very dif-ferent from one study to another and are justempirical data valuable for one food andprocess application in similar conditions. Toimprove kinetic models, a more precisereaction monitoring should be done in orderto control, anticipate and predict degrada-tion reactions better. In particular, monitor-ing of apocarotenals, apocarotenones andoxygen would be helpful. However, the the-oretical pathways are numerous, thus a pre-cise monitoring of all degradation reactionsseems impossible. Moreover, some reac-tions may be strongly correlated and it canbe hard to precisely attribute a quantifiedproduct to a specific reaction. A multidisci-plinary approach could help to simplify themonitoring of reactions. A literature reviewand thermodynamic analysis are interestingto highlight the more probabilistic path-ways. The examination of degradationkinetics is also necessary in order to identifythe most important reactions in terms of rate.The analytical considerations and the liter-ature review combined with the thermody-namic and kinetic data allow the building ofan observable degradation scheme whichshould represent the predominant path-ways. This observable degradation schemeshould include the main factors affecting thefate of the studied compound, such as timeand temperature, for instance, and shouldbe expressed through mathematical lan-guage, as Zepka et al. attempted to do in arough way [51]. By improving the complex-ity of the reaction scheme, a modellingapproach could combine mechanistic, ther-modynamic and kinetic considerations, ashas already been done for other chemicalreactions in food; for instance, the Maillardreaction [89]. Such models are very powerfulbecause they permit one to capitalise a lotof information. The effects of the factorsinvolved (duration time and temperature,for example) can be quantified and thebehaviour of the system can be predicted,which is very interesting from a knowledgeimprovement point of view. Conversely,these models allow the establishment of theoperating conditions necessary to obey a

Fruits, vol. 66 (6

) 435

436

C. Pénicaud et al.

quality criterion, such as a retention level inmicronutrients, for instance, but not onlywith one degree of freedom since the effectof several parameters can be introduced intothe model. Moreover, whilst empirical dataare generally based on time-consumingexperiments and have to be determined foreach new problem, such models are fullytransferable from one case to another, andcould thus be very useful for the food indus-try.

References

[1] Lewinsohn E., Sitrit Y., Bar E., Azulay Y.,Ibdah M., Meir A., Yosef E., Zamir D., TadmorY., Not just colors-carotenoid degradation asa link between pigmentation and aroma intomato and watermelon fruit, Trends FoodSci. Technol. 16 (2005) 407–415.

[2] Pallett K.E., Young A.J., Carotenoids, in: Als-cher, R.G., Hess, J.L. (Eds.), Antioxidants inhigher plants, CRC Press, Boca Raton, FL,U.S.A., 1993, 91–110.

[3] Gaziano J.M., Johnson E.J., Russell R.M.,Manson J.E., Stampfer M.J., Ridker P.M.,Frei B., Hennekens C.H., Krinsky N.I., Discri-mination in absorption or transport of β-carotene isomers after oral supplementationwith either all-trans- or 9-cis-β-carotene,Am. J. Clin. Nutr. 61 (2009) 1248–1252.

[4] Rodriguez-Amaya D.B., A guide to carote-noid analysis in foods, OMNI Research,Washington, D.C., U.S.A., 2001, 71 p.

[5] Dutta D., Dutta A., Raychaudhuri U., Chakra-borty R., Rheological characteristics andthermal degradation kinetics of β-carotene inpumpkin puree, J. Food Eng. 76 (2006) 538–546.

[6] Mortensen A., Analysis of a complex mixtureof carotenes from oil palm (Elaeis guineensis)fruit extract, Food Res. Int. 38 (2005) 847–853.

[7] Rios J.J., Fernández-García E., Mínguez-Mosquera M.I., Pérez-Gálvez A., Descriptionof volatile compounds generated by thedegradation of carotenoids in paprika,tomato and marigold oleoresins, FoodChem. 106 (2008) 1145–1153.

[8] Britton G., Liaaen-Jensen S., Pfander H.,Carotenoids, Vol. 1B: Spectroscopy,Birkhäuser-Verlag, Basel, Switzerland, 1995.

[9] Mohamed N., Hashim R., Rahman N.A., ZainS.M., An insight to the cleavage of β-caro-

tene to vitamin A: a molecular mechanicsstudy, J. Mol. Struct. 538 (2001) 245–252.

[10] Borel P., Drai J., Faure H., Fayol V., GalabertC., Laromiguiere M., Le Moel G., Recentknowledge about intestinal absorption andcleavage of carotenoids, Ann. Biol. Clin. 63(2005) 165–177.

[11] Laguerre M., Lecomte J., Villeneuve P., Eva-luation of the ability of antioxidants to coun-teract lipid oxidation: Existing methods, newtrends and challenges, Progr. Lipid Res. 46(2007) 244–282.

[12] Perez-Galvez A., Minguez-Mosquera M.I.,Structure-reactivity relationship in the oxida-tion of carotenoid pigments of the pepper(Capsicum annuum L.), J. Agric. Food Chem.49 (2001) 4864–4869.

[13] Ozhogina O.A., Kasaikina O.T., β-Caroteneas an interceptor of free radicals, Free Radic.Biol. Med. 19 (1995) 575–581.

[14] Warner K., Frankel E.N., Effects of β-caro-tene on light stability of soybean oil, J. Am.Oil Chem. Soc. 64 (1987) 213–218.

[15] Bureau S., Renard C.M.G.C., Reich M.,Ginies C., Audergon J.-M., Change in antho-cyanin concentrations in red apricot fruitsduring ripening, LWT - Food Sci. Technol. 42(2009) 372–377.

[16] Liu L.H., Zabaras D., Bennett L.E., Aguas P.,Woonton B.W., Effects of UV-C, red light andsun light on the carotenoid content and phy-sical qualities of tomatoes during post-har-vest storage, Food Chem. 115 (2009) 495–500.

[17] Bechoff A., Dhuique-Mayer C., Dornier M.,Tomlins K.I., Boulanger R., Dufour D.,Westby A., Relationship between the kine-tics of β-carotene degradation and formationof norisoprenoids in the storage of driedsweet potato chips, Food Chem. 121 (2010)348–357.

[18] Hiranvarachat B., Suvarnakuta P., Devahas-tin S., Isomerisation kinetics and antioxidantactivities of β-carotene in carrots undergoingdifferent drying techniques and conditions,Food Chem. 107 (2008) 1538–1546.

[19] Rodriguez E.B., Rodriguez-Amaya D.B., For-mation of apocarotenals and epoxycarote-noids from β-carotene by chemical reactionsand by autoxidation in model systems andprocessed foods, Food Chem. 101 (2007)563–572.

[20] Thurnham D.I., Bioequivalence of β-caroteneand retinol, J. Sci. Food Agric. 87 (2007)13–19.

Fruits, vol. 66 (6)

Degradation of β-carotene during processing or storage

[21] Zhang P., Omaye S.T., β-Carotene: interac-tions with α-tocopherol and ascorbic acid inmicrosomal lipid peroxidation, J. Nutr. Bio-chem. 12 (2001) 38–45.

[22] Mordi R.C., Mechanism of β-carotene degra-dation, Biochem. J. 292 (1993) 310–312.

[23] Stahl W., Sies H., Carotenoids and protec-tion against solar UV radiation, Skin Pharma-col. Appl. Physiol. 15 (2002) 291–296.

[24] Sander L.C., Sharpless K.E., Craft N.E., WiseS.A., Development of engineered stationaryphases for the separation of carotenoid iso-mers, Anal. Chem. (1994) 1667–1674.

[25] Britton G., Liaanen-Jensen S., Pfander H.,Carotenoids handbook, Birkhaüser VerlagBasel, Switz., 2004.

[26] Marx M., Stuparic M., Schieber A., Carle R.,Effects of thermal processing on trans-cis-isomerization of β-carotene in carrot juicesand carotene-containing preparations, FoodChem. 83 (2003) 609–617.

[27] Chen B.H., Huang J.H., Degradation andisomerization of chlorophyll a and β-caro-tene as affected by various heating and illu-mination treatments, Food Chem. 62 (1998)299–307.

[28] Henry L.K., Catignani G., Schwartz S., Oxi-dative degradation kinetics of lycopene,lutein, and 9-cis and all-trans-β-carotene, J.Am. Oil Chem. Soc. 75 (1998) 823–829.

[29] Vásquez-Caicedo A.L., Schilling S., Carle R.,Neidhart S., Effects of thermal processingand fruit matrix on β-carotene stability andenzyme inactivation during transformation ofmangoes into puree and nectar, Food Chem.102 (2007) 1172–1186.

[30] Schieber A., Marx M., Carle R., Simulta-neous determination of carotenes and toco-pherols in ATBC drinks by high-performanceliquid chromatography, Food Chem. 76(2002) 357–362.

[31] Kidmose U., Yang R.Y., Thilsted S.H., Chris-tensen L.P., Brandt K., Content of carote-noids in commonly consumed Asianvegetables and stability and extractabilityduring frying, J. Food Compos. Anal. 19(2006) 562–571.

[32] Koca N., Burdurlu H.S., Karadeniz F., Kine-tics of colour changes in dehydrated carrots,J. Food Eng. 78 (2007) 449–455.

[33] Dhuique-Mayer C., Tbatou M., Carail M.,Caris-Veyrat C., Dornier M., Amiot M.J.,Thermal degradation of antioxidant micronu-trients in citrus juice: kinetics and newly for-med compounds, J. Agric. Food Chem. 55(2007) 4209–4216.

[34] Caris-Veyrat C., Amiot M.J., Ramasseul R.,Marchon J.C., Mild oxidative cleavage ofβ-carotene by dioxygen induced by a ruthe-nium porphyrin catalyst: characterization ofproducts and of some possible interme-diates, New J. Chem. 25 (2001) 203–206.

[35] Nonier M.F., De Gaulejac N.V., Vivas N., VitryC., Characterization of carotenoids and theirdegradation products in oak wood. Inci-dence on the flavour of wood, C. R. Chim. 7(2004) 689–698.

[36] Sommerburg O., Langhans C.D., Arnhold J.,Leichsenring M., Salerno C., Crifo C.,Hoffmann G.F., Debatin K.M., Siems W.G.,β-Carotene cleavage products after oxida-tion mediated by hypochlorous acid – Amodel for neutrophil-derived degradation,Free Radic. Biol. Med. 35 (2003) 1480–1490.

[37] Bosser A., Belin J.M., Synthesis of β-Iononein an aldehyde/xanthine oxidase/β-carotenesystem involving free-radical formation, Bio-technol. Progress. 10 (1994) 129–133.

[38] Bosser A., Paplorey E., Belin J.M., A simpleway to (+/-)-dihydroactinidiolide from β-iononerelated to the enzymatic cooxidation ofβ-carotene in aqueous-solution, Biotechnol.Prog. 11 (1995) 689–692.

[39] Wache Y., Bosser-DeRatuld A., LhuguenotJ.C., Belin J.M., Effect of cis/trans isomerismof β-carotene on the ratios of volatile com-pounds produced during oxidative degrada-tion, J. Agric. Food Chem. 51 (2003) 1984–1987.

[40] Mordi R.C., Walton J.C., Burton G.W.,Hughes L., Keith I.U., David L.A., DouglasM.J., Oxidative degradation of β-caroteneand β-apo-8'-carotenal, Tetrahedron 49(1993) 911–928.

[41] Qiu D., Chen Z.R., Li H.R., Effect of heatingon solid β-carotene, Food Chem. 112 (2009)344–349.

[42] Kennedy T.A., Liebler D.C., Peroxyl radicalscavenging by β-carotene in lipid bilayers -Effect of oxygen partial-pressure, J. Biol.Chem. 267 (1992) 4658–4663.

[43] Tsuchihashi H., Kigoshi M., Iwatsuki M., NikiE., Action of β-carotene as an antioxidantagainst lipid peroxidation, Arch. Biochem.Biophys. 323 (1995) 137–147.

[44] Furr H.C., Analysis of retinoids and carote-noids: Problems resolved and unsolved, J.Nutr. 134 (2004) 281S–285S.

[45] Wu X., Sun C.J., Yang L.H., Zeng G., Liu Z.Y.,Li Y.M., β-Carotene content in sweet potatovarieties from China and the effect of prepa-ration on β-carotene retention in the Yanshu

Fruits, vol. 66 (6

) 437

438

C. Pénicaud et al.

No. 5, Innov. Food Sci. Emerg. Technol. 9(2008) 581–586.

[46] Shin J.H., Chung H.L., Seo J.K., Sim J.H.,Huh C.S., Kil S.K., Baek Y.J., Degradationkinetics of Capsanthin in paprika (Capsan-thin annuum L.) as affected by heating, J.Food Sci. 66 (2001) 15–18.

[47] Achir N., Randrianatoandro V.A., Bohuon P.,Laffargue A., Avallone S., Kinetic study of β-carotene and lutein degradation in oilsduring heat treatment, Eur. J. Lipid Sci. Tech-nol. 112 (2010) 349–361.

[48] Avallone S., Rojas-Gonzalez J.A., TrystramG., Bohuon P., Thermal sensitivity of someplantain micronutrients during deep-fatfrying, J. Food sci. 74 (2009) C339–C347.

[49] Fratianni A., Cinquanta L., Panfili G., Degra-dation of carotenoids in orange juice duringmicrowave heating, LWT - Food Sci. Tech-nol. 43 (2010) 867–871.

[50] Baldermann S., Naim M., Fleischmann P.,Enzymatic carotenoid degradation andaroma formation in nectarines (Prunus per-sica), Food Res. Int. 38 (2005) 833–836.

[51] Zepka L.Q., Borsarelli C.D., Azevedo M.A.,da Silva P., Mercadante A.Z., Thermal degra-dation kinetics of carotenoids in a cashewapple juice model and its impact on the sys-tem color, J. Agric. Food Chem. 57 (2009)7841–7845.

[52] Melendez-Martinez A.J., Vicario I.M., Here-dia F.J., Application of tristimulus colorimetryto estimate the carotenoids content in ultra-frozen orange juices, J. Agric. Food Chem.51 (2003) 7266–7270.

[53] Vikram V.B., Ramesh M.N., Prapulla S.G.,Thermal degradation kinetics of nutrients inorange juice heated by electromagnetic andconventional methods, J. Food Eng. 69(2005) 31–40.

[54] Limbo S., Torri L., Piergiovanni L., Light-induced changes in an aqueous β-carotenesystem stored under halogen and fluores-cent lamps, affected by two oxygen partialpressures, J. Agric. Food Chem. 55 (2007)5238–5245.

[55] Cheftel J.C., Introduction à la biochimie et àla technologie des aliments, Tech. & Doc.Lavoisier, Paris, France, 1992.

[56] Liu M.H., Chen B.H., Relationship betweenchlorophyll a and β-carotene in a lipid-containing model system during heating,Food Chem. 61 (1998) 41–47.

[57] Emenhiser C., Watkins R.H., Simunovic N.,Solomons N., Bulux J., Barrows J., SchwartzS.J., Packaging preservation of β-carotene

in sweet potato flakes using flexible film andan oxygen absorber, J. Food Qual. 22 (1999)63–73.

[58] Baiano A., Tamagnone P., Marchitelli V., delNobile M.A., Quality decay kinetics of semi-preserved sauce as affected by packaging,J. Food Sci. 70 (2005) E92–E97.

[59] Nhung D.T.T., Bung P.N., Ha N.T., PhongT.K., Changes in lycopene and β-carotenecontents in aril and oil of gac fruit during sto-rage, Food Chem. 121 (2010) 326–331.

[60] Takahashi A., Shibasaki-Kitakawa N.,Yonemoto T., Kinetic model for autoxidationof β-carotene in organic solutions, J. Am. OilChem. Soc. 76 (1999) 897–903.

[61] Takahashi A., Shibasaki-Kitakawa N., Toshi-kuni Y., A rigorous kinetic model for β-caro-tene oxidation in the presence of anantioxidant, α-tocopherol, J. Am. Oil Chem.Soc. 80 (2003) 1241–1247.

[62] Takahashi A., Suzuki J.-I., Shibasaki-Kita-kawa N., Toshikuni Y., A kinetic model for co-oxidation of β-carotene with oleic acid, J.Am. Oil Chem. Soc. 78 (2001) 1203–1207.

[63] Shibasaki-Kitakawa N., Hideto K., TakahashiA., Toshikuni Y., Oxidation kinetics of β-caro-tene in olein acid solvent with addition of anantioxidant, α-tocopherol, J. Am. Oil Chem.Soc. 81 (2004) 389–394.

[64] Aho L., Wahlroos O., A comparison betweendeterminations of the solubility of oxygen inoils by exponential dilution and chemicalmethods, J. Am. Oil Chem. Soc. 44 (1967)65–66.

[65] Benson B.B., Krause D.J., The concentrationand isotopic fractionation of oxygen dis-solved in freshwater and seawater in equili-brium with the atmosphere, Limnol.Oceanogr. 29 (1984) 620–632.

[66] Battino R., Evans F.D., Danforth W.F., Solubi-lities of seven gases in olive oil with refe-rence to theories of transport through cellmembrane, J. Am. Oil Chem. Soc. 45 (1968)830–833.

[67] Ke P.J., Ackman R.G., Bunsen coefficient foroxygen in marine oils at various tempera-tures determined by an exponential dilutionmethod with a polarographic oxygen elec-trode, J. Am. Oil Chem. Soc. 50 (1973) 429–435.

[68] Pénicaud C., Guilbert S., Peyron S., GontardN., Guillard V., Oxygen transfer in foodsusing oxygen luminescence sensors:Influence of oxygen partial pressure andfood nature and composition, Food Chem.123 (2010) 1275–1281.

Fruits, vol. 66 (6)

Degradation of β-carotene during processing or storage

[69] Pénicaud C., Peyron S., Gontard N.,Guillard, V., Oxygen quantification methodsand application to the determination of oxy-gen diffusion and solubility coefficients infood, Food Rev. Int. (2011), doi:10.1080/87559129.2011.595021.

[70] Holst G., Glud R.N., Kühl M., Klimant I., Amicrooptode array for fine-scale measure-ment of oxygen distribution, Sens. ActuatorsB 38–39 (1997) 122–129.

[71] Haralampu S.G., Karel M., Kinetic-modelsfor moisture dependence of ascorbic-acidand β-carotene degradation in dehydratedsweet-potato, J. Food Sci. 48 (1983) 1872–1873.

[72] Mortensen A., Skibsted L.H., Kinetics andmechanism of the primary steps of degrada-tion of carotenoids by acid in homogeneoussolution, J. Agric. Food Chem. 48 (2000)279–286.

[73] Assuncao R.B., Mercadante A.Z., Carote-noids and ascorbic acid composition fromcommercial products of cashew apple (Ana-cardium occidentale L.), J. Food Compos.Anal. 16 (2003) 647–657.

[74] Goulson M.J., Warthesen J.J., Stability andantioxidant activity of β-carotene in conven-tional and high oleic canola oil, J. Food Sci.64 (1999) 996–999.

[75] Budowski P., Brondi A., Autoxidation ofcarotene and vitamin A influence of fat andantioxidants, Arch. Biochem. Biophys. 89(1960) 66–73.

[76] Pérez-Gálvez A., Mínguez-Mosquera M.I.,Degradation, under non-oxygen-mediatedautooxidation, of carotenoid profile presentin paprika oleoresins with lipid substrates ofdifferent fatty acid composition, J. Agric.Food Chem. 52 (2004) 632–637.

[77] Sambanthamurthi R., Sundram K., Tan Y.-A.,Chemistry and biochemistry of palm oil,Prog. Lipid Res. 39 (2000) 507–558.

[78] Zhang P., Omaye S.T., β-Carotene and pro-tein oxidation: effects of ascorbic acid and α-tocopherol, Toxicology 146 (2000) 37–47.

[79] Haila K.M., Lievonen S.M., Heinonen M.I.,Effects of lutein, lycopene, annatto, and γ-tocopherol on autoxidation of triglyceride, J.Agric. Food Chem. 44 (1996) 2096–2100.

[80] Palozza P., Calviello G., Bartoli G.M., Prooxi-dant activity of β-carotene under 100% oxy-gen pressure in rat liver microsomes, FreeRadic. Biol. Med. 19 (1995) 887–892.

[81] Packer L., Antioxidant action of carotenoidsin vitro and in vivo and protection against

oxidation of human low–density lipo-pro-teins, Ann. N. Y. Acad. Sci. 691 (1993) 48–60.

[82] Polyakov N.E., Leshina T.V., KonovalovaT.A., Kispert L.D., Carotenoids as scaven-gers of free radicals in a fenton reaction:antioxidants or pro-oxidants? Free Radic.Biol. Med. 31 (2001) 398–404.

[83] Boon C.S., McClements D.J., Weiss J., Dec-ker E.A., Role of iron and hydroperoxides inthe degradation of lycopene in oil-in-wateremulsions, J. Agric. Food Chem. 57 (2009)2993–2998.

[84] Simpson D.J., Baqar M.R., Lee T.H., Finestructure of the chromoplasts of fruit of Sola-num aviculare Forth. var. Brisbanense, Aust.J. Bot. 26 (1978) 783–792.

[85] Vasquez-Caceido A.L., Heller A., NeidhartS., Carle R., Chromoplast morphology andβ-carotene accumulation during postharvestripening of mango cv. ‘Tommy Atkins’, J.Agric. Food Chem. 54 (2006) 5769–5776.

[86] Olatunde Farombi E., Britton G., Antioxidantactivity of palm oil carotenes in organic solu-tion: effects of structure and chemical reac-tivity, Food Chem. 64 (1999) 315–321.

[87] Nguyen M., Francis D., Schwartz S., Thermalisomerisation susceptibility of carotenoids indifferent tomato varieties, J. Sci. Food Agric.81 (2001) 910–917.

[88] Abushita A.A., Daood H.G., Biacs P.A.,Change in carotenoids and antioxidant vita-mins in tomato as a function of varietal andtechnological factors, J. Agric. Food Chem.48 (2000) 2075–2081.

[89] Martins S., Van Boekel M., A kinetic modelfor the glucose/glycine Maillard reactionpathways, Food Chem. 90 (2005) 257–269.

[90] Kim Y.-N., Giraud D.W., Driskell J.A., Toco-pherol and carotenoid contents of selectedKorean fruits and vegetables, J. Food Com-pos. Anal. 20 (2007) 458–465.

[91] Kandlakunta B., Rajendran A., ThingnganingL., Carotene content of some common(cereals, pulses, vegetables, spices andcondiments) and unconventional sources ofplant origin, Food Chem. 106 (2008) 85–89.

[92] Bhaskarachary K., Rao D.S.S., DeosthaleY.G., Reddy V., Carotene content of somecommon and less familiar foods of plant ori-gin, Food Chem. 54 (1995) 189–193.

[93] Bora P.S., Rocha R.V.M., Narain N., Moreira-Monteiro A.C., Moreira R.A., Characteriza-tion of principal nutritional components ofBrazilian oil palm (Eliaes guineensis) fruits,Bioresour. Technol. 87 (2003) 1–5.

Fruits, vol. 66 (6

) 439

440

C. Pénicaud et al.

[94] Ngoh Newilah G., Dhuique-Mayer C., Rojas-Gonzalez J.A., Tomekpe K., Fokou E., EtoaF.X., Carotenoid contents during ripening ofbanana hybrids and cultivar grown in Came-roon, Fruits 64 (2009) 197–205.

[95] Dhuique-Mayer C., Caris-Veyrat C., OllitraultP., Curk F., Amiot M.J., Varietal and interspe-cific influence on micronutrient contents incitrus from the Mediterranean area, J. Agric.Food Chem. 53 (2005) 2140–2145.

[96] Giuffrida D., Dugo P., Salvo A., Saitta M.,Dugo G., Free carotenoid and carotenoidester composition in native orange juices ofdifferent varieties, Fruits 65 (2010) 277–284.

[97] Goula A.M., Adamopoulos K.G., Kineticmodels of β-carotene degradation during airdrying of carrots, Dry. Technol. 28 (2010)752–761.

[98] Holdsworth S.D., Thermal processing ofpackaged foods, Blackie Acad. & Prof.,Lond., U.K., 1997.

[99] Ahmed J., Shivhare U.S., Sandhu K.S., Ther-mal degradation kinetics of carotenoids andvisual color of papaya puree, J. Food Sci. 67(2002) 2692–2695.

[100]Henry L.K., Catignani G.L., Schwartz S.J.,Oxidative degradation kinetics of lycopene,lutein, and 9-cis and all-trans β-carotene, J.Am. Oil Chem. Soc. 75 (1998) 823–829.

La degradación del β-caroteno en el curso de la transformación o delalmacenamiento de las frutas y verduras: mecanismos reactivos y aspectoscinéticos.Resumen — Introducción. La significativa disminución de la calidad de las frutas y verdurasen el curso de su transformación preocupa mucho a la industria alimentaria. Los micronutrientesestán particularmente afectados y, entre ellos, el β-caroteno que presenta interesantes propie-dades sensoriales, nutricionales y biológicas. La literatura que trata la degradación del β-carotenoes muy densa, pero la naturaleza de las conclusiones difiere, en función de que el acercamientodel problema sea biológico, químico o tecnológico. Nuestro artículo propone una síntesis depuntos de vista complementarios en el estudio del β-caroteno durante la transformación y elalmacenamiento de los alimentos. Reacciones de degradación. Los principales compuestosde degradación del β-caroteno identificados son los isómeros, los epóxidos, los apocarotenalesy los productos de clivaje de cadena corta, entre los cuales figuran los compuestos de aromas.De la información sacada de la literatura se puede deducir un esquema reactivo detallado delas reacciones de isomerización y de auto-oxidación del β-caroteno. Las principales vías estánbien documentadas, pero el esquema reactivo global permanece incompleto. Además, lamayoría de los estudios del mecanismo se llevan a cabo según un sistema modelo, por lo quedicha información no puede representar bien el comportamiento del β-caroteno en los alimentosreales. Cinéticas durante los procesos y el almacenamiento. La determinación de las ciné-ticas de degradación permite identificar las reacciones más rápidas, es decir, generalmente, lasque tienen los impactos fuertes, así como cuantificar el efecto de los factores que pueden dis-minuir el contenido de β-caroteno. La temperatura, la presencia de oxígeno, la composición yla estructura afectan significativamente la velocidad de pérdida de β-caroteno. Sin embargo, lasmetodologías empleadas para obtener los parámetros cinéticos son muy importantes y, final-mente, la mayoría de los resultados encontrados en la literatura son específicos de un estudioy difícilmente generalizables. Discusión y conclusión. Los enfoques de mecanismos y de ciné-ticas proporcionan, individualmente, datos informativos interesantes para mejorar la compren-sión y el seguimiento del β-caroteno. La combinación del conjunto de esta información, juntoa otras consideraciones termodinámicas y analíticas, permite construir esquemas reactivos obser-vables que pueden posteriormente ser transcritos en modelos matemáticos. Mediante este acer-camiento multidisciplinario, que hoy apenas se emplea, podrían capitalizarse los conocimientosy podrían desarrollarse herramientas para mejorar la retención del β-caroteno durante las trans-formaciones alimentarias y el almacenamiento.

Francia / frutas / hortalizas / almacenamiento / procesamiento / carotinoides /isomerización / oxidación / degradación / reacciones químicas

Fruits, vol. 66 (6)