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Shelf life prolongation of fruit juices through essential oils and homogenization: a review

A. Bevilacqua, M.R. Corbo, D. Campaniello, D. D'Amato, M. Gallo, B. Speranza and M. Sinigaglia

Department of Food Science, Faculty of Agricultural Science, University of Foggia, via Napoli 25, 71122 Foggia, Italy

This chapter proposes an overview of juice microbiology, then focusing on the effectiveness of essential oils and plant extracts for the inhibition of pathogenic and spoiling microorganisms. Finally, there is a brief overview on juice homogenization, highlighting its benefits and limits for the prolongation of juice shelf life

Keywords fruit juices; shelf life; safety; spoiling microorganisms; natural antimicrobials; alternative approaches

1. General remarks

Codex Alimentarius defines juice as “the fermentable but unfermented juice, intended for direct consumption, obtained by the mechanical process from sound, ripe fruits, preserved exclusively by physical means. The juice must have the characteristic colour, flavour and taste typical of the fruit from which it comes, it may be turbid or clear. The juice may have been concentrated and later reconstituted with water suitable for the purpose of maintaining the essential composition and quality factors of the juice. The addition of sugars or acids can be permitted but must be endorsed in the individual standard” [1]. Juices may be prepared from nearly all fruits, if desired; the most common ones include pineapple, orange, grapefruit, mango and passion fruit. Nevertheless, any fruits (e.g. banana, fig) can be easily pureed, but it is more expensive to produce a clear juice from the pulp. Generally juice is classified as puree, when the resulting consistency is a fluid that pours very slowly, or pulp when it pours even more slowly. Juices can be concentrated for preservation, handling and storage and then reconstituted before consumption. Nectars are made from fruit juices, to which water and sugar have been added; they contain a proscribed minimum of juice, ranging from 25 to 50%. Table 1 reports the classification of different types of drink made from fruits. Flow chart for juice production is simple; a generalized scheme is reported in Appendix I.

Table 1 Designation of different kind of drinks made from fruits [2].

Type Description Pure juice 100% Pure fruit juice with nothing added, not from concentrate From concentrate Made from concentrate, reconstituted and pasteurized Not from concentrate Pasteurized after extraction Chilled, ready to serve Made from concentrate or pasteurized juice, held refrigerated Fresh squeezed Not pasteurized, held refrigerated Fresh frozen Unpasteurized, frozen after extraction Juice blend A mixture of pure juices Puree Pulp-containing, more viscous than juices, totally fruit Nectar Pulpy or clear. Sugar, water and acid added, 25 to 50% juice* Nectar base Possesses sufficient flavour, acid and sugar to require water dilution for consumption* Juice drink Contains 10 to 20% juice* Juice beverage Contains 10 to 20% juice* Juice cocktail Contains 10 to 20% juice* Fruit + ade (e.g. Lemonade) Contains >10% fruit juice, sugar and water* Juice extract Fruit extracted by water, then concentrated*

*Standards for juice solids minimum varies from country to country

2. Juice microflora

Fruit juices contain water, sugars, organic acids, vitamins, and trace elements thus providing an ideal environment for spoilage by microorganisms; on the other hand, they generally have a lower pH (pH<4.5), thus the common feature of their potential spoilage agents is that they must be acid-loving microorganisms. The most commonly encountered microbial genera are Acetobacter, Alicyclobacillus, Bacillus, Clostridium, Gluconobacter, Lactobacillus, Leuconostoc, Saccharobacter, Zymomonas, and Zymobacter. However, yeasts are predominant because of their high acid tolerance

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and the ability of many of them to grow anaerobically. Pichia, Candida, Saccharomyces and Rhodotorula are the genera mainly involved in spoiled juices; the species frequently isolated are Pichia membranifaciens, Candida maltosa, C. sake, Saccharomyces bailii, S. bisphorus, S. cerevisiae, S. rouxii, S. bayanus, Brettanomyces intermedius, Schizosaccharomyces pombe, Torulopsis holmii, Hanseniaspora guilliermondii, Schwanniomyces occidentalis, Dekkera bruxellensis, Torulaspora delbruckii, Zygosaccharomyces microellipsodes, and D. naardenensis. A high level of yeast contamination in fruit juices may be indicative of poor plant hygiene. Most spoilage yeasts are highly fermentative, forming ethanol and CO2 from sugar, causing split cans and cartons, and explosions in glass or plastic bottles (table 2). Amongst the spoilage yeasts, P. membranifaciens is considered as the target microorganism for the optimisation of thermal treatments of juices because it is resistant to heat as well as to moderate amounts of salt, SO2, sorbic, benzoic and acetic acids [3-5]. Acid-tolerant bacteria able to grow in juices include lactic acid (Lactobacillus and Leuconostoc spp.) and acetic acid bacteria (Acetobacter and Gluconobacter spp.), Propionibacterium cyclohexanicum, Bacillus coagulans, B. megaterium, B. macerans, B. polymyxa, B. licheniformis and B. subtilis. Lact. plantarum var. mobilis, Lact. brevis, Leuconostoc mesenteroides and L. dextranicum are known to cause vinegary, buttermilk off-odours and off-flavours in frozen concentrated orange juice; Bacillus species are known to cause flat-sour type spoilage in acidic fruit beverages, because of the production of lactic acid without gas formation (table 2). Lact. plantarum, Lact. brevis and B. coagulans are amongst the most resistant bacteria to thermal treatments [3, 5]. In 1982, a new type of spoilage bacterium emerged in a large scale spoilage incident in Germany, during which flat-sour type spoilage with offensive smelling medicinal or antiseptic characteristics was noted in commercial pasteurised apple juice. The microbe responsible for the incident was a thermo-acidophilic, endospore-forming bacterium, later identified as Alicyclobacillus acidoterrestris [6]. To date, 20 species and 2 subspecies that belong to this genus have been identified and more spoilage incidents have been reported in various fruit juices, fruit juice blends, carbonated fruit juice drinks, fruit pulps and lemonades, with apple juice as the product most often involved [7]. A. acidoterrestris is the species primarily responsible for spoilage incidents, although other species, including A. acidiphilus, A. pomorum, A. hesperidum, A. herbarius, A. cycloheptanicus and A. acidocaldarius have also been implicated due to their ability to produce taint compounds [7]. Most spoilage incidents occurred in spring or summer and spoilage consisted mainly in an off-flavour or –odour production, with or without sediment; sometimes discolouration or cloudiness occurred (table 2). Consumer complaints were often the only reason for companies becoming aware of the problem, since the absence of gas production made spoilage difficult to detect. The off-flavour and -odour detected have been described as medicinal, disinfectant-like, antiseptic, phenolic, smoky and hammy and, in most cases, they have been identified as the chemical compound guaiacol. Although guaiacol seems to be the dominant cause of taint, the halophenols 2,6-dichlorophenol (2,6-DCP) and 2,6-dibromophenol (2,6-DBP) have been also implicated [7, 8]. Additionally, heat resistant species of mycelial fungi such as Byssochlamys fulva, Byssochlamys nivea, Neosartorya fischeri, Talaromyces flavus, Talaromyces macrosporus, Monascus purpureus, Paecilomyces fulvus, Aspergillus versicolor, A. restrictus, and some species of Eupenicillium (E. brefaldianum, E. lapidosum) are reported to spoil fruit juices, pulps and concentrates. Mold growth can result in an off-flavour or odor that may be described as “stale” or “old”, development of a mycelial mat, reduction in sugar content, and mycotoxin production (see table 2) [3, 5].

Table 2 Microorganisms related to spoilage in fruit juices.

Microorganism Spoilage effect Highly fermentative yeasts Production of ethanol and CO2 from sugars, formation of biofilm, bulging or

exploding of containers Acetobacter, Gluconobacter Oxidation of ethanol, fermentation, turbidity Lactobacillus, Leuconostoc Sour or off-taste, buttermilk off-flavour, gummy slime or ropiness, production

of acetic acid, CO2, ethanol Clostridium spp. Production of gas, a strong butyric odor, and increased acidity A. acidoterrestris Phenolic or antiseptic odour or off-flavour with or without light sediment or

slight haze Bacillus spp. Flat sour Zymomonas, Saccharobacter, Zymobacter

Ethanol production

Heat resistant moulds Off-flavour or odour like “stale” or “old”, development of a mycelial mat, reduction in sugar content, mycotoxin production

3. Safety of fruit juices

Numerous serious safety problems associated with fruit juices consumption are documented (table 3) [9, 10]. In the last decade, in North America over 1700 people have fallen ill after consuming juice and cider. Most of these outbreaks

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involved unpasteurized juices such as apple, orange, lemon, pineapple, carrot, coconut, cane sugar, banana, acai and mixed fruit juices. The most common pathogens were Escherichia coli O157:H7 and O111, Salmonella sp., Cryptosporidium and norovirus. A few other outbreaks were due to Vibrio cholerae, Cl. botulinum and yeasts. All reported cases of contamination by pathogenic microorganisms were due to unpasteurized juices, and E. coli is one of the most studied bacteria. Numerous dangerous strains of E. coli exist and are able to produce toxins of various types and toxicities that cause different diseases. The enterohemorrhagic (EHEC) class is of most concern, due to its low infectious dose and its association with hemorrhagic colitis (HC), hemolytic uremic syndrome (HUS), and thrombotic thrombocytopenic purpura (TTP). In 2004 the Center for Disease Control reported an serious outbreak of 213 illnesses associated with apple cider consumption in New York, due to Shiga toxin–producing E. coli O111 together with C. parvum (table 3). The fresh-pressed untreated apple cider was produced at an orchard and sold directly and exclusively to consumers [5, 9]. Salmonella infections are commonly associated with animal-derived foods, such as meat, seafood, dairy, and egg products, rather than juices. However, outbreaks associated with fresh juice have occurred as far back as 1922. Early outbreaks resulting in typhoid fever were associated with poor hygiene by asymptomatic Salmonella Typhi shedding food handlers. As disinfection of water, sanitation procedures, and hygiene practices have improved, outbreaks of typhoid fever have become far less common in developed countries. Nonetheless, given the dramatic increase of fresh fruit imported from developing countries, typhoid fever outbreaks associated with these commodities remain a concern. More recent outbreaks of nontyphoidal salmonellosis in fresh juice have been attributed to fecal-associated contamination of fruit or poor processing practices. In 2005, 152 cases of Salmonella Typhimurium infection associated with commercially distributed unpasteurized orange juice were reported (table 2). Upon inspection, Food and Drug Administration (FDA) found that the production facility did not comply with the HACCP plan and that noncompliance likely contributed to this outbreak [5, 9]. Cryptosporidium parvum is a highly infectious protozoan parasite causing persistent diarrhea. Common reservoirs are ruminants including cattle and sheep. Infection with cryptosporidium does not always result in severe disease symptoms and the organism is far more dangerous for the immunocompromised. Cryptosporidium is more commonly associated with contaminated water; its oocysts are thick-walled, resistant to chlorine, and persistent. Presumably, the thick wall also confers some acid resistance, as outbreaks of cryptosporidiosis have also occurred from fresh-pressed cider. In 2003 a Cryptosporidium parvum outbreak was reported in Ohio with 144 infections associated with commercially distributed apple cider (table 3). The cider was treated with ozone and sold directly to consumers and businesses. Investigation deemed the ozone treatment insufficient to decrease the probability of contamination [5, 9]. In addition to pathogenic bacteria, several new pathogenic yeasts, including C. famata, C. guillermondii, C. krusei, and C. parapsilosis can cause spoilage of fruit juices. These new pathogens are very unlikely to affect healthy individuals but are of concern in immunocompromised patients. Several species of molds are capable of producing different mycotoxins in fruit juices. Mycotoxins, particularly patulin, represent a potent food safety hazard. Some molds, e.g. Penicillium expansum, P. griseofulvum, P. roqueforti var. carneum, P. funiculosum, P. claviforme, P. granulatum, and Byssochlamys spp., produce patulin in apple juice, while others, such as Neosartorya produce fumitremorgins, terrein, verruculogen, and fischerin. Byssochlamys species also produce byssotoxin A and byssochlamic acid. Other mycotoxins produced in fruit juice by molds include ochratoxin A, citrinin, and penicillic acid [3]. Viruses are not very common in fruit juices, even if a serious outbreak from the virus Hepatitis A was recorded in 2004 involving european tourists returned from Egypt (table 2). Finally, although not implicated in foodborne outbreaks associated with fresh juices, another important pathogen is Listeria monocytogenes because its ability to grow at conventional refrigeration temperatures and under acidic conditions. L. monocytogenes is ubiquitous within the environment, carried by animals, and frequently found on fruits. The minimum pH for growth of L. monocytogenes is dependant on the acidulant. For malic acid, one acid found in juices, the lowest pH value for growth of L. monocytogenes is from 4.4 to 4.6 depending on the strain. This pathogen causes listeriosis, a serious disease with complications including meningitis, septicemia and spontaneus abortion in immocompromised individuals and pregnant woman [3, 5].

Table 2 Examples of fruit juice-associated outbreaks, reported by CSPI, from 2000 to 2011 [9, 10].

Year Microorganism N° outbreaks Countries Juice type 2000 Salmonella Enteridis 143 USA Orange 2003 Cryptosporidium parvum 144 Ohio Apple 2004 Escherichia coli O111

and C. parvum 213 New York Apple

2004 Virus Hepatitis A 351 Multiple European countries Orange 2005 Salmonella Tyhimurium 152 Multiple states Orange 2008 Salmonella Panama 33 Netherlands Orange 2010 E. coli O157:H7 7 Maryland and Pennsylvania Apple

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4. Essential oils in juices

Consumer interest towards natural and friendly compounds caused in the past a renewed attention on alternative natural antimicrobial from plant origin, i.e. plant extracts (essential oils, aldehydes, esters), herbs and spices. A brief focus on these antimicrobials is reported in appendix 2. Essential oils (EOs) are aromatic oily liquids, obtained from plant materials (flowers, buds, seeds, leaves, twig bark, herbs, wood, fruits and roots), which can be obtained by fermentation, extraction or distillation [11, 12]. EOs are constituted of a complex mix of various compounds, including terpenes, alcohols, chetones, phenols, acids, aldehydes, and esters [12]; they are referred to as GRAS compounds [13], both as flavouring substances and antimicrobial hurdles against a wide range of microorganisms, including bacteria, yeasts and moulds [14]. Many authors reported on the effectiveness of EOs and their active compounds to inactivate and/or inhibit spoiling and pathogenic microorganisms in juices. Their effects relies upon some main elements: the pH of the product, the kind and the concentration of EO and the microorganism. Concerning pH, it is generally accepted that a low pH improves the action of EOs by increasing their hydrophobicity. Gutierrez et al. [15, 16] found that the antibacterial efficacy of oregano and thyme EOs was very high when pH was 4.33–5.32. However, this general statement was not confirmed for yeasts. Tserennadmid et al. [17] studied the anti-yeast activity of some EOs (clary sage, juniper, lemon and marjoram) and used pH values ranging between 4.0 and 7.0; they found that acididic pHs had only slight effects on the growth of yeasts. Moreover, the inhibitory effect of EOs was maximal at pH 7 but remained good also in the acidic range, thus suggesting that the ionization form of the EO components did not play a major role for the acidophilic yeasts. The storage temperature is another key-factor for the antimicrobial activity of EOs. Friedman et al. [18], in fact, found that the antimicrobial activity of some EOs towards E. coli O157:H7 and Salmonella Hadar inoculated in apple juice was higher at 37°C than at 4 and 21°C, due probably to a higher partition coefficient of oils and to an enhanced fluidity bacterial membrane. Both EOs and active compounds (an active compound is the major componet of an essential oil) have been proposed and used for juice stabilization; some examples are cinnamon, clove, lemon, lemongrass, lime and oregano oils, citrus extract (representative of EOs) and carvacrol, cinnamaldehyde, eugenol, citral geraniol, D-limonene (representative of active compounds of EOs) [14, 19-23]. A brief synopsis of the application of EOs in fruit juices is reported in table 4.

Table 4 Application of EOs in juices

EOs and active compounds Microorganisms Juice Oils and extracts Cinnamon oil Clove oil Citrus extract Lemon oil Lemongrass oil Lime oil Oregano oil Active compounds Carvacrol Cinnamaldehyde Citral Eugenol Geraniol D-limonene

Spoiling bacteria Alicyclobacillus acidoterrestris Bacillus coagulans Lactobacillus plantarum Lact. brevis Pathogens Escherichia coli O157:H7 Listeria monocytogenes Salmonella sp. Yeasts Geotrichum candidum Pichia anomala P. membranifaciens Rhodotorula bacarum Saccharomyces cerevisiae S. bayanus Schizosaccharomyces pombe Moulds Aspergillus spp. Fusarium oxysporum Penicillium spp.

Apple Melon Orange Pear Pineapple Strawberry Tomato Watermelon

A new approach for EOs use in foods was proposed by Donsì et al. [24], who used a nano-encapsulation system (sun flower and palm oils as organic phases; glycerol monooleate, soy lecithin, tween 20 and Cleargum(R) as emulsifying agents) for the entrapment of a mixture of terpenes and D-limonene. They studied the antimicrobial activity of this system towards S. cerevisiae, E. coli and Lact. delbrueckii and found a higher effect of nano-encapsulated compounds in pear and orange juices in preserving the sensorial properties of juices.



In general, EOs possess a strong antimicrobial activity against spoiling and pathogenic microflora of juices, being the effect greater at low pH; however, the use of some essential oils in fruits juices is not recommended because of their adverse effect on the sensory properties. Therefore, combinations with other preservation methods are required to decrease their impact on food flavour [12].

5. Homogenization and combined approaches

Fruit juices, thanks to their composition, viscosity, and fluidity can be treated successfully through high pressure homogenization (HPH). Samples of orange juice were inoculated with L. innocua ATCC 33090 at a concentration of 7.0 log cfu/ml and pressurised at 300 MPa through the primary homogenizing valve and at 30 MPa on the secondary homogenizing valve [25]. L. innocua viable counts and injured cells were measured periodically after Ultra HPH treatment. Cell counts decreased by approximately 2.5 log units during 18 days. Welti-Chanes et al. [26] evaluated the effect of different HPH treatment (0-250 MPa with a maximum of five passes) on natural microflora of orange juice and found that 5 passes at 100 MPa were required to reduce at 2.93 and 3.27 log cfu/ml mesophilic bacteria and yeasts/moulds, respectively. Saldo et al. [27] applied a HPH processing to apple juice and recovered that a treatment at 200 MPa reduced cell count to the undetectable level. Maresca et al. [28] used a multi-pass HPH treatment (pressure level: 0-250 MPa; number of passes: 1-5) for the pasteurization of orange, red orange, pineapple and Annurca apple juices, thus they found that a 3-pass-HPH treatment at 150 MPa achieved the complete inactivation of S. cerevisiae (previously inoculated in orange, red orange and pineapple juices) as well as the stabilization of endogenous microflora of fresh Annurca apple juice. Patrignani et al. [29, 30] studied the potentialities of HPH (100 MPa for 1-8 passes) to inactivate S. cerevisiae 635 and Zygosaccharomyces bailii, in apricot and carrot juices. Initial inoculum levels of S. cerevisiae were about 3 and 6 log cfu/ml, whereas initial inoculum level of Z. bailii was 5 log cfu/g. They confirmed the significance of the number of passes, pressure level and food matrix on the effectiveness of HPH. HPH treatment was considered a good option for non thermal production of Annurca apple juice by Donsì et al. [31], Who applied homogenization at different pressure levels (150-300 MPa) for the inactivation of endogenous microflora; thus the shelf life of clear juice and juice with pulp could be prolonged for many weeks upon HPH treatment at 250 and 300 MPa. Table 4 proposes a summary of HPH use in juices.

Table 4 Application of HPH in juices

Juice Targets Effect on juice characteristics Apple Carrot Mango Pinepple Orange Tomato

Alicyclobacillus acidoterrestris Escherichia coli O157.H7 Listeria monocytogenes Lactic acid bacteria Saccharomyces cerevisiae Emericella nidulans Fusarium oxysporum Penicillium expansum Aspergillus niger Talaromyces macrosporus

Stabilization of cloudy appearance No effect on pH, color, content of vitamin C and phenols Inhibiton of enzymatic activities

In order to reduce the negative effect on HPH and EOs on food quality, the application of combined hurdles was studied. Hurdle technology is based on the concept of applying a combination of some mild treatments to gradually reduce or inhibit microbial counts, with a better retention of sensory properties and nutritive value than those obtained using only a single process [32] Concerning the combined application of HPH with other treatments, some examples are the papers of Pathanibul et al. [33], Kumar et al. [34], Tribst et al. [35] and Bevilacqua et al. [36]. Pathanibul et al. [33] homogenized apple and carrot juices with high pressure in a range from 0 to 350 MPa in combination with nisin (10 IU/ml) to inactivate E. coli and L. innocua (ca. 7 log cfu/ml); E. coli seemed more sensitive than L. innocua, as a reduction of 5 log cfu/ml was achieved at pressures > 250 MPa. E. coli was also inactivated in apple juice and cider using a combination of seven levels of pressures (from 50 to 350 MPa) and two type of chitosan, regular and water soluble, (0.01 and 0.1%) by Kumar et al. [34]. In particular, HPH induced significant inactivation in the range of 100 to 200 MPa; when HPH treatment was combined with incremental quantities of chitosan (both types), a synergistic effect was observed. These results were more evident in apple juice than apple cider at same homogenizing pressures. Tribst et al. [35] applied HPH and thermal treatment on A. niger conidia inoculated in mango nectar and they concluded that 5.03 minutes of thermal treatment and 300 MPa reduced mould by 5 log cfu/ml, with a synergistic effect. Finally, Bevilacqua et al. [36] studied the combination of citrus extract (0-3 ppm), benzoate (0-300 ppm) and

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homogenization (0-90 MPa) for the inhibition of Pichia membranifaciens; the centroid approach was used to combine the three variables and point out their individual and interactive effects. Thus they found that citrus extract could be a suitable alternative for the inhibition of P. membranifaciens in acidic drinks, as a low amount of this compound (3 ppm) increased the lag phase by 60–70%. In addition, homogenization (90 MPa) was able to reduce significantly the initial cell number.

6. Conclusions and future perspectives

The use of alternative approaches for juice stabilization appears as a promising trend, due to the increased awareness of consumers towards natural, fresh and nutrient-enriched foods. Juices are usually referred as “vitamin containing foods”; therefore, the use of a processing able to retain vitamins and nutrients or minimize their loss could be advisable. However, some issues related to EOs and homogenization should be solved, i.e.:

1.The organoleptic impact of EOs. It would be advisable the use of extracts and/or oils water-soluble, odourless and colourless. 2.The optimization of homogenization and/or combined approaches, in order to make possible a real industrial production (costs, volumes, shelf life duration).

Briefly, why and how use EOs and HPH in juices? Figure 1 could be a possible answer.

PROCESSING GREEN CONSUMERISM

Reduce initial contamination

Control post-processing contamination

Retain or minimize the loss of nutrients. Use friendly compounds

Thermal treat.

Thermal treat.

Thermal treat.

HPH EOs

HPH

HPH

EOs

EOs

SOLUTION. Use a combined approach (HPH+EOs) to:

Reduce the initial contamination

Control post-processing contamination

Retain sensorial and nutritional quality

Figure 1. Why use Essential oils and homogenization in juices? A possible answer. (EOs, essential oils; HPH, homogenization; thermal treat., thermal treatment).



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[34] Kumar S, Thippareddi H, Subbiah J, Zivanovic S, Davidson PM, Harte F. Inactivation of Escherichia coli K-12 in apple juice using combination of high-pressure homogenization and chitosan. Journal of Food Science. 2009; 78:M8-M14.

[35] Tribst AAL, Franchi MA, de Massaguer PR, Cristianini M. Quality of mango nectar processed by high-pressure homogenization with optimized heat treatment. Journal of Food Science. 2011; 76:M106-M110.

[36] Bevilacqua A, Corbo MR, Sinigaglia M. Inhibition of Pichia membranifaciens by homogenization and antimicrobials. Food and Bioprocess Technology. 2010; doi: 10.1007/s11947-010-0450-1.



AP

PE

ND

IX 1

Jui

ce p

rodu

ctio

n

Sta

ge in

pro

cess

Q

ual

ity

Ass

uran

ce

Met

hod

s

Har

vest

frui

t

Che

ck f

or f

ull m

atur

ity.

Sel

ect m

atur

e, u

ndam

aged

fru

its. A

ny f

ruits

that

are

mou

ldy

or u

nder

-ri

pe s

houl

d be

sor

ted

and

rem

oved

.

Was

h

N

eces

sary

to r

emov

e st

ones

, lea

ves

and

soil

. T

he s

elec

ted

frui

ts a

re w

ashe

d in

a tr

ough

usi

ng p

otab

le w

ater

.

So

rt /

grad

e

Insp

ectio

n an

d re

mov

al o

f un

soun

d fr

uit i

s ve

ry im

port

ant,

beca

use

afte

r ju

icin

g on

e pi

ece

of d

efec

tive

fru

it c

an e

nd u

p co

ntam

inat

ing

an e

ntir

e lo

t of

juic

e.

Insp

ectio

n ca

n be

man

ual,

cont

inge

nt u

pon

wor

kers

obs

ervi

ng a

nd

rem

ovin

g de

fect

s or

aut

omat

ic, e

ffec

ted

by c

ompu

ter

cont

rolle

d se

nsor

s to

det

ect o

ff c

olou

r, s

hape

or

size

.

Cut

/slic

e/co

re

Nec

essa

ry to

pee

l the

fru

it a

nd r

emov

e st

ones

or

seed

s. I

f ne

cess

ary,

cho

p th

e fr

uit i

nto

piec

es th

at w

ill f

it in

to th

e liq

uidi

ser

or p

ulpe

r.

Thi

s st

age

is n

eces

sary

for

som

e ty

pe o

f fr

uit (

e.g.

pin

eapp

le).

The

fru

its

are

peel

ed, c

ored

and

des

eed

man

uall

y or

with

aut

omat

ic m

achi

ne,

depe

ndin

g on

the

scal

e of

ope

ratio

n.

Ju

ice

extr

acti

on

It is

ess

entia

l to

wor

k qu

ickl

y be

twee

n th

e ex

trac

tion

of th

e ju

ice

and

the

bottl

ing

stag

e. E

xtra

cted

fru

it ju

ice

that

is le

ft to

st

and

in th

e he

at w

ill s

tart

to f

erm

ent a

nd m

ay s

tart

to

disc

olou

r du

e to

enz

yme

activ

ity.

The

re a

re s

ever

al m

etho

ds to

ext

ract

juic

e de

pend

ing

on th

e ty

pe o

f fr

uit

you

use.

App

les

are

pres

sed,

whe

reas

mel

on a

nd p

apay

a ar

e st

eam

ed to

re

leas

e th

e ju

ice.

Pul

per

is u

sed

for

pine

appl

es, m

ango

, str

awbe

rry

and

othe

r fl

eshi

ng f

ruits

.

Filt

er/c

lari

ficat

ion

of ju

ice

Che

ck th

e pr

oduc

tion

of a

cle

ar o

r br

illia

ntly

cle

ar ju

ice

and

the

prev

entio

n of

pos

t filt

ratio

n tu

rbid

ity.

Rap

id m

etho

ds s

uch

as c

entr

ifug

atio

n an

d fi

ltra

tion

can

pro

duce

a c

lear

ju

ice.

Jui

ces

whe

re a

clo

ud is

des

ired

gen

eral

ly d

o no

t req

uire

filt

ratio

n;

cent

rifu

gatio

n is

ade

quat

e. S

omet

imes

may

be

nece

ssar

y to

use

pec

tic

enzy

mes

to b

reak

dow

n th

e pe

ctin

and

to h

elp

clea

r th

e ju

ice.

Dea

erat

ion

Che

ck th

e le

vels

of

diss

olve

d ox

ygen

. Cle

arly

, onc

e ai

r is

re

mov

ed o

r re

plac

ed b

y in

ert g

as, t

he ju

ice

mus

t be

prot

ecte

d fr

om th

e at

mos

pher

e in

all

subs

eque

nt p

roce

ssin

g st

eps.

Dea

erat

ion

can

be a

ccom

plis

hed

by e

ithe

r fl

ashi

ng th

e he

ated

juic

e in

to

a va

cuum

cha

mbe

r or

sat

urat

ing

the

juic

e w

ith a

n in

ert g

as. N

itrog

en o

r ca

rbon

dio

xide

is b

ubbl

ed th

roug

h th

e ju

ice

prio

r to

sto

ring

und

er a

n in

ert a

tmos

pher

e.

F

ill a

nd s

eal

C

heck

fill

-wei

ght a

nd c

orre

ctly

sea

led

pack

. T

he m

ixed

juic

e is

bot

tled

and

cork

ed, e

ither

man

ually

or

with

au

tom

atic

bot

tle f

illin

g m

achi

ne, d

epen

ding

on

the

scal

e of

ope

ratio

n.

H

eat

H

eat

It is

nec

essa

ry to

des

troy

enz

ymes

and

mic

roor

gani

sms.

The

te

mpe

ratu

re a

nd ti

me

of h

eatin

g ar

e cr

itic

al f

or a

chie

ving

bot

h th

e co

rrec

t she

lf li

fe o

f th

e dr

ink

and

reta

inin

g a

good

col

our

and

flav

our.

If T

etra

bri

ck is

to b

e us

ed f

or p

acka

ging

the

juic

e, b

ulk

past

euri

zatio

n w

ould

be

done

bef

ore

the

pack

agin

g.

Alte

rnat

ivel

y, th

e bo

ttled

juic

e is

pas

teur

ized

at a

pre

dete

rmin

ed

tem

pera

ture

and

tim

e us

ing

a pa

steu

rize

r.

Hot

filli

ng in

to

bottl

es

The

cor

rect

wei

ght s

houl

d be

fill

ed in

to th

e pa

ckag

es e

ach

tim

e.

Tet

ra b

rick

pac

kage

s ca

n al

so b

e us

ed. T

he p

rodu

cts

shou

ld b

e ho

t-fi

lled

into

cle

an, s

teri

lized

bot

tles.

Coo

l, la

bel a

nd s

tore

C

heck

the

labe

l and

sto

rage

con

ditio

ns a

re c

orre

ct.

The

pas

teur

ized

juic

e is

all

owed

to c

ool a

nd th

en a

rran

ged

in c

orru

gate

d ca

rton

s an

d se

aled

.

1165©FORMATEX 2011


APPENDIX 2 Alternative natural antimicrobials from plant origin Antimicrobials Definition/details Essential oils (EOs) Aromatic oily liquids obtained from plant material by fermentation,

extraction or distillation. They are a mixture of many compounds, some of them labelled as "major component", the other present as traces. The majority of EOs are regarded as GRAS component

Active compounds Major component of EOS; some examples are eugenol, cinnamaldehyde, thymol, carvacrol, menthol. Generally, they possess a phenolic structure.

Aldehydes and esters Aldehydes are dominant compounds released by plant tissue through the lipoxygenase pathway after some damage. Some examples of aldehydes showing an antimicrobial effect are hexenal, trans-2-hexenal and hexyl-acetate. Vanillin is included in aldehyde groups; although it is regarded as GRAS compound, its use as antimicrobial in juice is limited by the fact that some microorganisms, like A. acidoterrestris, are able to catabolize vanillin for the production of guaiacol (responsible of a severe off-flavour in juices).

Herbs and spices There are few data on the use of herbs and spice in juices as antimicrobial compounds; some example are mint and cinnamon powder.



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