Original article

1 Technol. Sector-Fed. Univ.Paraná, PO Box 19011,Curitiba PR, Brazil,nandarobert@hotmail.com,nandarobert@gmail.com2 Dep. Chem. Biol.,Fed. Technol. Univ. Paraná,Curitiba PR, Brazil3 Dep. Food Sci. Technol.,Cent. Agric. Sci.,Fed. Univ. Santa Catarina,Florianópolis SC, Brazil4 Dep. Biochem. Mol. Biol.,Fed. Univ. Paraná,PO Box 19031, Curitiba PR,Brazil

Evaluation of the chemical characteristics and rheological behavior of pitaya (Hylocereus undatus) peel Fernanda Robert DE MELLO1*, Cláudia BERNARDO3, Carolinne Odebrecht DIAS3, Luana Carolina BOSMULER ZÜGE1,Joana Léa MEIRA SILVEIRA4, Edna Regina AMANTE3, Lys Mary BILESKI CANDIDO2

* Correspondence and reprints

Received January 4, 2014Accepted March 4, 2014

Fruits, 2014, vol. 69, p. 381–390© 2014 Cirad/EDP SciencesAll rights reservedDOI: 10.1051/fruits/2014028www.fruits-journal.org

RESUMEN ESPAÑOL, p. 390

Evaluation of the chemical characteristics and rheological behavior of pitaya(Hylocereus undatus) peel.

Abstract – Introduction. Pitaya peel has been applied as a functional ingredient for fooddue to the presence of betacyanins. However its polysaccharides can also contribute as a tex-ture agent for food. The aim of this work was to evaluate the chemical characteristics andrheological behavior of the pitaya peel. Materials and methods. The samples were analyzedwith regard to moisture and mineral content, protein, lipids, sugar, fiber, vitamin C, titratableacidity, soluble solids content and pH. Rheological measurements were performed on rheo-meter through flow curve, stress sweep, frequency sweep and the variation of temperature.Results and discussion. The results showed that pitaya peel is rich in insoluble fibers andexhibits non-Newtonian behavior, characteristic of a strong gel with a predominance of solidcharacter. Furthermore, samples showed thermal resistance at the conditions of frequency,tension and temperature analyzed. Conclusion. Considering our results, in addition to use asa natural colorant in food, pitaya peel can also contribute to the nutritional value and textureof the products.

Brazil / Hylocereus undatus / fruits / byproducts / peel / chemical composition /fibers / rheological properties

Évaluation des caractéristiques chimiques et du comportement rhéologiquede la pelure du pitaya (Hylocereus undatus).

Résumé – Introduction. La pelure du pitaya est utilisée comme ingrédient alimentaire enraison de la présence de bétacyanines. Cependant ses polysaccharides peuvent égalementcontribuer à la nutrition en tant qu'agent de texture. Le but de notre travail a été d'évaluer lescaractéristiques chimiques et le comportement rhéologique de la pelure de pitaya. Matérielet méthodes. Des échantillons de pelure de pitaya ont été analysés quant à leur teneur enhumidité et en sels minéraux, protéines, lipides, sucres, fibres, vitamine C, acidité titrable,matières solides solubles, ainsi que leur pH. Des mesures rhéologiques ont été effectuéesavec un rhéomètre en étudiant la courbe d'écoulement, le balayage du fluage, le balayage defréquence et la variation de température. Résultats et discussion. Les résultats ont montréque la pelure de pitaya est riche en fibres insolubles et présente un comportement non-new-tonien, caractéristique d'un gel avec prédominance d’un caractère solide. En outre, les échan-tillons ont montré une résistance thermique aux conditions de fréquence, tension ettempérature de l’analyse. Conclusion. Compte tenu de ces résultats, en plus d'être appliquéeen tant que colorant naturel dans l'alimentation, la pelure de pitaya pourrait également contri-buer à la valeur nutritionnelle et à la texture des produits.

Brésil / Hylocereus undatus / fruits / sous-produit / pelure / compositionchimique / fibre / propriété rhéologique

Fruits, vol. 69 (5) 381

Article published by EDP Sciences

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1. Introduction

Pitaya is a tropical fruit and its name, of Anti-llean origin, means scaly fruit. This fruitbelongs to the Cactaceae family from whichvarious species of epiphytic cacti of thegenus Hylocereus and Selenicereus, nativeto Mexico and Central and South America,are also cultivated in the countries of South-east Asia [1, 2].

Hylocereus undatus is the most cultivatedand consumed species of pitaya. The fruitsof this species present market demand, dueto its very attractive sensory characteristics.

Despite considerable research on itsnutritional importance, medicinal and foodvalue, the pitaya is still a culture not widelyused and exploited [3]. The fruit has a highnutritional value, and is rich in calcium,phosphorus, potassium and vitamins. Fur-thermore, it can also be considered as asource of carbohydrates and fibers [4, 5].

Studies conducted with the pitaya em-phasized its functional properties helping toreduce the risk of chronic diseases and itspotential to contribute to physical and men-tal wellness [6–8]. Pulp showed antioxidants[9, 10], and oligosaccharides with prebioticproperties [8]. Pitaya peel presented highquantities of antioxidants [11]. Moreover, itsseeds are rich in essential fatty acids andphytosterols [12, 13].

The pitaya peel represents up to one thirdof the fruit weight; it is considered a residueof the pitaya processing industry [14, 15].The waste of fruit and vegetable processingis traditionally considered an environmentalproblem, however it has been increasinglyused for the extraction of compounds suchas pigments [16]. Pitaya peels may be sub-jected to simple and economical purificationmethods to provide extracts and sub-frac-tions for the formulation of healthcare prod-ucts and food applications [15].

Aside from being rich in antioxidants [11]and phenolic compounds [17], pitaya peelpresents high concentration of fibers andpolysaccharides which are responsible of itstexture and rheological behavior, and canbe useful for the food industry as a textureagent.

According to Jamilah et al., the total fibercontent of pitaya is very high (69.3%), ofwhich 56.50% corresponds to insoluble fiber(IF) and 14.82% to soluble fiber (SF) [14].The main polysaccharides present arepectins, hemicelluloses and cellulose, ligninand starch. Pectin fractions were mainlycomposed of arabinose, galactose andrhamnose, while the hemicellulose fractionmainly consisted of glucose and xylose [18].

Knowledge of the rheological propertiesof raw materials used in the food industryis essential for the development of new foodproducts, because different materials willrespond differently to external forces whichthey are subjected to [19].

The rheological behavior of fluid foodsuch as fruit juices and pulps is a factor ofgreat importance in the design of equip-ment in the food industry; in addition, it isone of the factors that helps to evaluate thequality of the product. The rheologicalbehavior of these materials, which aremainly comprised of water and the varioussolids, such as soluble and insoluble fibers,results from the interaction between theseelements contributing alone, or potentiatedwhen combined [19].

Therefore, pitaya peel presents highpotential as a functional ingredient for foodwhich can improve its nutritional value andtexture. The aim of our study was to evalu-ate the chemical composition and rheolog-ical behavior of the pitaya peel in order toprovide information which could be helpfulfor its application in food products.

2. Materials and methods

2.1. Materials

Samples of pitaya (Hylocereus undatus)(figure 1) were harvested at Embrapa,Brasília, Brazil, in 2011 and 2012, January.The fruits (30 units) were packaged andtransported to the Laboratory of Fruits andVegetables of the Federal University of SantaCatarina, where they were stored at a tem-perature of 6 °C.

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Characteristics and rheological behavior of pitaya

The reagents used were all of analyticalgrade. The enzymes α-amylase, protease,amyloglucosidase were obtained fromMegazyme (Ireland). The other reagents(sodium hydroxide, ether, sulphuric acid,anhydrous sodium sulfate, copper sulfate,boric acid, ethanol, hydrochloric acid,oxalic acid, ascorbic acid, sodium dichlo-rophenolindophenol (DCFI), zinc acetate,copper sulfate, sodium potassium tartrate,acetone, zinc acetate, potassium ferrocya-nide) were obtained from Vetec (Rio deJaneiro, Brazil). The water used was filteredthrough a deionization system (Milli-Qdeionizer, Millipore, Bedford, USA).

2.2. Methods

2.2.1. Sample preparation

The fruits were washed and manually sep-arated in exocarp (dirt, scales and cladodefragments), mesocarp (peel and endocarp)and pulp with seeds (figure 2).

The fresh mesocarp was used for chem-ical analysis. Part of the pitaya peel wasdehydrated in an oven (DLS04, DeLeo,Brazil) at 45 °C for about 12 h. Sampleswere ground in a grinder mill (Q298 A21,Quimis, Brazil) in order to obtain a homo-geneous mixture which was passed throughstandard sieves of 100 mesh (150 µm) foranalysis.

For the rheological analysis, dehydratedpitaya peels were rehydrated with 90%water and homogenized (L4RT, SilversonMachines Ltd., U.K.) at 9000 rpm for 3 min.

2.2.2. Chemical characterization

The chemical analysis was performed withthe mesocarp of three fruits of each harvest(2011 and 2012).

Analyses of fibers (soluble and insoluble)and sugars (reducing and non-reducing)were performed in duplicate. All other ana-lyzes were performed in triplicate accordingto the standards recommended by the Asso-ciation of Official Analytical Chemists(AOAC) [20].

The pH readings were taken with a digitalpH meter (Q-400A, Quimis, Brazil) cali-brated with buffers 4.0 and 7.0. The values

of soluble solids (°Brix) were obtained ona digital refractometer (LLI 58,318, MettlerToledo, Switzerland). The titratable aciditywas measured by titration with 0.1 mol⋅L–1

NaOH and acidity expressed as percentstandard solution.

The moisture content was obtained byoven drying (DLS04, DeLeo, Brazil) at105 °C until constant weight. The ash wasdetermined by incinerating the sample at550 °C in a muffle (Q-318M24, Quimis,

Figure 1.Pitaya fruit (Hylocereus undatus).

FPecbuAw

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igure 2.reparation of samples forvaluating chemicalharacteristics and rheologicalehavior of pitaya (Hylocereusndatus) peel.color figure is available atww.fruits-journal.org.

) 383

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F.R. de Mello et al.

Brazil) to constant weight. The protein wasanalyzed by the Kjeldahl method, based onnitrogen determination by digestion oforganic matter. Lipids were extracted withethylic ether by the Soxhlet method.

The soluble and insoluble fibers weredetermined through enzymatic-gravimetricmethods. The non-reducing and reducingsugars were determined by acid hydrolysisand the results expressed in reducing car-bohydrates into glucose and non-reducingcarbohydrates as sucrose. The vitamin Ccontent was quantified by the Tillmansmethod based on reducing sodium2,6-dichlorophenolindophenol (DCFI) andexpressed as mg of ascorbic acid.100 g–1 ofthe product.

2.2.3. Rheological analysis

Rheological measurements were performedon rheometer (Mars II, Thermo ElectronGmbH, Germany) coupled to a thermostaticbath (K15, Haake, Germany), a thermocirculator water (DC5, Haake, Germany),and a thermal controller (Peltier, Haake,Germany), using sensor plate-plate.

The flow curves were obtained applyingshear rates ranging from 0.1 to 300 s-1 at25 °C, with 100 data acquisition points, intriplicate. The results obtained from the flowcurve were fitted using the powerlaw (Ostwald-de-Waele): τ = k (γ)n, and theHerschel-Bulkley model: τ = τ0 + k (γ)n [21,22], where τ = shear stress (Pa), τ0 = yieldstress (Pa), γ = shear rate (s–1), K = consist-ency index (Pa⋅s–1), n = flow behavior index(dimensionless).

The parameters k and n are widely usedin the characterization of fluids. For a New-tonian fluid, n = 1. When n is different to1, a non-Newtonian fluid is characterized. Inthis case, if n is less than 1, the fluid showspseudoplastic behavior, and if n is morethan 1, the fluid shows dilatant behavior.The k values are related to the resistance tofluid flow [23].

A stress sweep was performed in therange of (0.1 to 10) Pa at frequencies of(1 and 10) Hz at 25 °C, in order to verify thelinear viscoelastic range and to select thestrain that would be used to perform thefrequency sweep and temperature ramps.

The frequency sweep was then conductedapplying the preselected strain, increasingthe oscillatory frequency over time from (0.1to 100) Hz at 25 °C.

The rheological behavior of the samplewasalso evaluated with variation of temperature,using a heating program of 3 °C⋅min–1,increasing the temperature from (5 to95) °C, at a frequency of 1 Hz. In order toprevent solvent evaporation, a layer of min-eral oil was applied around the rheometerplate. This temperature range was chosendue to the storage temperature in the refrig-erator, approximately 5 °C, and the pasteur-ization temperature of fruit juices, approxi-mately 95 °C.

3. Results and discussion

3.1. Chemical characterization

According to our results, pitaya peel has ahigh concentration of water (2011 harvest =90.23%; 2012 harvest = 84.86%) (table I).Jamilah et al. reported that pitaya peel fromHylocereus polyrhizus species presents92.65% moisture content [14].

The samples showed low concentra-tions of mineral content (2011 harvest,0.17 g⋅ 100 g–1; 2012 harvest, 0.22 g⋅100 g–1),proteins (2011 harvest, 0.64 g⋅100 g–1; 2012harvest, 0.66 g⋅100 g–1) and lipids (2011harvest, 0.02 g⋅100 g–1; 2012 harvest,0.07 g⋅100 g–1) (table I). The protein con-tent of pitaya varies considerably from(0.3 to 1.5) g⋅100 g–1 [24, 25]. This differ-ence can be attributed to the methodolo-gies applied or to the possible interferenceof other nitrogen compounds such asbetalains.

Pitaya peel from the 2011 harvest pre-sented less reducing sugars (0.70 g⋅100 g–1)than that of the 2012 harvest (2.62 g⋅100 g–1)(table I). Wichienchot et al. reported thatthe main reducing sugars of pitaya are glu-cose and fructose [8].

The non-reducing sugar levels werelower than 0.5 g.100 g–1 in all samples ana-lyzed. This result is in agreement with

Fruits, vol. 69 (5)

Characteristics and rheological behavior of pitaya

Fruits, vol. 69 (5

Tab

leI.

Che

mic

alch

arac

teris

tics

ofp

itaya

(Hyl

ocer

eus

und

atus

)pee

lfro

msa

mp

lings

don

eon

the

2011

and

2012

harv

ests

.Dat

aar

eth

eav

erag

efr

omth

ree

rep

etiti

ons.

Yea

rof

harv

est

Moi

stur

eco

nten

tM

iner

alco

nten

tP

rote

inLi

pid

sR

educ

ing

suga

rsN

on–

red

ucin

gsu

gars

Sol

uble

fiber

Inso

lub

lefib

erV

itam

inC

(mg.

100

g–1)

Titr

atab

leac

idity

(mg

mal

icac

id.1

00g–1

)

Sol

uble

solid

s(° B

rix)

pH

(%)

2011

90.2

3±

0.25

00.

17±

0.00

50.

64±

0.00

20.

02±

0.00

80.

70±

0.00

0<

0.5

2.14

±0.

002.

90±

0.00

7.62

±2.

210.

22±

0.06

7.15

±0.

055.

48±

0.06

2012

84.8

6±

0.65

00.

22±

0.18

00.

66±

0.00

60.

07±

0.03

02.

62±

0.02

0<

0.5

1.30

±0.

995.

70±

0.71

7.04

±0.

880.

25±

0.04

12.7

7±

1.01

4.83

±0.

03

) 385

386

F.R. de Mello et al.

Stintzing et al. who reported that the pitayajuice is devoid of sucrose [25].

Physicochemical properties of dietaryfiber include solubility, viscosity, water andoil holding capacity, stabilizing, gel-formingand fermentation. Compared with insolubledietary fiber, in food processing, the solublefraction demonstrates greater capacity toprovide viscosity, ability to form gels and/or act as emulsifiers. Insoluble fiber usuallyhas high water-holding capacity.

Insoluble fiber (IF) was present in greaterquantity than soluble fiber (SF) in all sam-ples. The [IF/SF] ratio was [2.90/2.14] in the2011 harvest and [5.70/1.30] in the 2012 har-vest. Jamilah et al. reported that pitaya peelpresents a relation of [IF/SF] of [3.8/1.0] [14].According to Horn, the recommended ratioof [IF/SF] in food is [3/1] [26]. Therefore, thepitaya peel from the 2012 crop presented agood [IF/SF] ratio, indicating the presence ofdietary fiber with good physiological effect.

Different values were obtained byZhuang et al. that determined the contentsof total fiber (TF), soluble fiber (SF), insol-uble fiber (IF) of fiber rich powders (FRP)from pitaya peels with different particlesize [27]. Dried peels were milled andmeshed through the 80 (FRP 80), 140 (FRP140) and 250 (FRP 250) meshes. Resultsshowed that FRP 140 had the highest totalfiber (79.37%) and soluble fiber (33.07%)with a balanced ratio of [SF/IF] [1.00/1.32].The [SF/IF] ratios of FRP 80, and FRP 250were [1.00/1.99], and [1.00/1.41], respec-tively. The particle size of milled peelsaffected the fiber compositions.

From the physiological viewpoint, die-tary fiber generally has properties such asdecreased intestinal transit time andincreased stool bulk; it is fermentable bycolonic micro flora; it reduces total bloodand/or LDL cholesterol levels; it reducespostprandial blood glucose and/or insulinlevels, contributing to reduction in the riskof chronic disorders, e.g., coronary heartdisease, diabetes, obesity and some formsof cancer [28, 29].

The soluble fibers present in pitaya peelcan help in the digestive process, neutralizetoxic substances such as heavy metals andmay be associated with the regulation of

blood sugar in people with type II diabetes[5]. Moreover, pitaya peel presents mucilagethat can have a positive influence on cho-lesterol metabolism [30].

Hadi administered pitaya extracts tohyperglycemic rats and observed that, afterseven weeks of supplementation, the miceshowed reduced levels of glucose in theblood, triglycerides and LDL cholesterol,and increased levels of HDL cholesterol andantioxidants in the plasma [31].

Pitaya is a fruit with low levels ofvitamin C [4]. Pitaya peel presented (7.62and 7.04) mg⋅100 g–1 of vitamin C inthe 2011 and 2012 harvests, respectively(table I). Although low, these levels ofvitamin C are in the same range of otherfruits, such as apple (6.0 mg⋅100 g–1) andplum (3.0 mg⋅100 g–1) [32]. Choo and Yongreported that the pitaya pulp with seeds pre-sented 31.1 mg⋅100 g–1 of vitamin C whilepitaya fruit (pulp + seeds + peel) presented11.6 mg⋅100 g–1 of vitamin C [33].

Pitaya peel has low acidity: (0.22 and0.25) mg of malic acid⋅100 g–1 of samplefor the 2011 and 2012 harvests, respectively(table I). The acidity and soluble solidscontent of the fruits are considered asimportant quality criteria for the flavor clas-sification. The total acidity decreases withfruit ripening due to the respiration processand use of organic acids as substrates inmetabolic reactions [34].

Pitaya peel presented (7.15 and12.77) °Brix for the 2011 and 2012 harvests,respectively (table I). Chitarra and Chitarrareported that the fruits in general have amean soluble solid between (8.0 and14.0) °Brix [35]. Junqueira et al. found thatvalues of soluble solids of pitaya pulpranged between 13.0–15.0 °Brix [2].

The pH values for pitaya peel were high(2011 harvest: 5.48; 2012 harvest: 4.83).These results are in agreement with Stintz-ing et al. [25] and Fernandes et al. [36] whoreported that pitaya pulp has a pH of 4.82and 4.6, respectively.

3.2. Rheological analysis

Our results regarding ground pitaya peelin water showed that the flow curve

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Characteristics and rheological behavior of pitaya

obtained exhibited a nonlinear relationshipbetween the shear stress and shear rate(figure 3), thus demonstrating non-Newto-nian behavior.

The deviation from Newtonian behaviorof the solution of ground pitaya peel can bejustified by the presence of insoluble parti-cles and suspended insoluble materials con-sisting of pectin and polysaccharides.Furthermore, pitaya peel is rich in insolublefibers (2011 harvest: 2.90 g⋅100 g–1; 2012:5.70 g⋅100 g–1) which exert a significantinfluence on their rheological behavior.

The results obtained with the flow curveswere fitted by power law (Ostwald-de-Waele), these being: consistency index (k) =131.61 ± 0.80, flow behavior index (n) =0.20 ± 0.00 and R2 = 0.99; and Herschel-Bulkley model: yield stress (τ0) = 6.36 ± 0.05,

consistency index (k) = 132.14 ± 6.34, flowbehavior index (n) = 0.20 ± 0.01 andR2 = 0.99. These values confirmed that theflow curves are typical of pseudoplastic flu-ids, because the value of (n) is less than 1(0.20) in both models, with a good correla-tion coefficient (R2 = 0.99). The Herschel-Bulkley model shows that the yield stress isnot significant, since its value is lower thanthe standard deviation.

Krokida et al. performed a study compar-ing various rheological data available inthe literature for fruit pulps, includingguava, raspberry, pineapple, apricot, apple,mango, tamarind, and blackcurrant andfound that all these pulps fruit exhibit pseu-doplastic behavior [37].

The effect of the ground pitaya peel inwater sample on the mechanical responsewas investigated by dynamic oscillatorytests. These assessments are sensitive tochanges in chemical composition and in thephysical structure of the samples due to thecharacteristics of non-destructive measuringmethod. Stress sweep experiments (1.0 Hzand 10.0 Hz) were carried out to ensure thatthe frequency sweep measurements wereperformed within the linear viscoelasticregion. Considering the mechanical spectraof the pitaya peel sample, dynamic oscilla-tory results showed G’ (elastic modulus) >G” (viscous modulus) throughout the entirefrequency range (0.1–10 Hz), showing vis-coelastic solid behavior with a gel-like struc-ture. The moduli G’ and G’’ are dependenton the frequency (figure 4). According toRao, a weak gel presents G’ and G’’ depend-ent on the frequency and low rangebetween G’ and G’’, like that shown for thepitaya peel sample [38].

Montoya-Arroyo et al. reported thatpitaya peel has high viscosity values at lowconcentrations and the shear-thinning flowbehavior showed interesting similarities tothat of commercial thickeners like locusbean gum and guar gum [18]. Therefore,pitaya pericarp is suggested to be a prom-ising alternative to these commercial gums.

To evaluate their thermal stability, theground pitaya peel in water sample was sub-mitted to temperature variations, from 5 °Cto 95 °C at 3 °C per min. Results show

She

ar s

tress

(Pa)

Figure 3.Flow curve of pitaya peel sample representing theshear rate dependence of the shear stress,recorded at 25 °C.

Figure 4.Effect of frequency on storage modules (G':elastic modulus) and loss (G'': viscous modulus)of pitaya peel throughout the entire frequencyrange (0.1–10 Hz).

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thermally stable pitaya peel sample duringheating from 5 °C to 95 °C (figure 5). In theanalyzed temperature range, the elasticmodulus (G') remained above the viscousmodulus (G''). The sample retained solidcharacter with heating, suggesting that thesample’s behavior does not display majorchanges during the storage and heatingprocesses.

Therefore, ground pitaya peel in watershowed the rheological behavior of a stronggel with a predominance of solid characterand thermo stability at the conditions of fre-quency, tension and temperature analyzed.The predominance of insoluble fibers canjustify this rheological behavior of the pitayapeel at several temperatures.

4. Conclusion

Pitaya peel can be suggested for use as afunctional ingredient for food products dueto its nutritional value, especially for thepresence of high fiber content. Moreover,pitaya peel can be considered as a textureagent, due to its strong gel behavior andthermo stability at the heating and coolingconditions.

Acknowledgements

The authors are grateful to EmbrapaCerrado for providing the pitaya samplesand technical information, and to Dr NiltonTadeu Vilela Junqueira for providing scien-tific information on the pitaya fruit.

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Evaluación de las características químicas y del comportamiento reológicode la cáscara de la pitahaya (Hylocereus undatus).

Resumen – Introducción. La cáscara de la pitahaya se emplea como ingrediente alimenta-rio, ya que presenta betacianinas. Sin embargo sus polisacáridos pueden contribuir también ala nutrición como agente de textura. El objetivo de nuestro estudio fue el de evaluar las carac-terísticas químicas y el comportamiento reológico de la cáscara de la pitahaya. Material ymétodos. Se analizaron muestras de cáscara de pitahaya en cuanto a su contenido de hume-dad y de sales minerales, proteínas, lípidos, azúcares, fibras, vitamina C, acidez valorable,materias sólidas solubles, así como su pH. Se efectuaron medidas reológicas con un reóme-tro, para estudiar la curva de flujo, el barrido de la fluencia, el barrido de frecuencia y lavariación de temperatura. Resultados y discusión. Los resultados mostraron que la cáscarade la pitahaya es rica en fibras insolubles y presenta un comportamiento no Newtoniano,característica de un gel con predominancia de un carácter sólido. Además, las muestras reve-laron una resistencia térmica a las condiciones de frecuencia, tensión y temperatura del análi-sis. Conclusión. Habida cuenta de estos resultados, además de aplicarse como colorantenatural en la alimentación, la cáscara de pitahaya podría asimismo contribuir al valor nutricio-nal y a la textura de los productos.

Brasil / Hylocereus undatus / frutas / subproductos / piel (vegetal) /composición química / fibras / propiedades reológicas

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