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Scientia Horticulturae 199 (2016) 15–22

Contents lists available at ScienceDirect

Scientia Horticulturae

journa l h om epage: www.elsev ier .com/ locate /sc ihor t i

mpact of storage conditions and variety on quality attributes androma volatiles of pitahaya (Hylocereus spp.)

avid Obenlanda,∗,1, Marita Cantwellb, Ramiro Loboc, Sue Collind, Jim Sievertd,ary Lu Arpaiad

USDA, Agricultural Research Service, San Joaquin Valley Agricultural Sciences Center, 9611 South Riverbend Avenue, Parlier, CA 93648-9757, United StatesDepartment of Plant Sciences, University of California, Davis, CA 95616, United StatesUniversity of California Cooperative Extension, San Diego, CA 92123, United StatesDepartment of Botany and Plant Sciences, University of California, Riverside, CA 92521, United States

r t i c l e i n f o

rticle history:eceived 9 October 2015eceived in revised form 7 December 2015ccepted 11 December 2015vailable online 28 December 2015

eywords:ensoryntioxidantetacyaninugarsrganic acids

a b s t r a c t

Pitahaya are increasing in popularity but knowledge on the effects of storage and the potential impactof variety on subsequent quality following storage is incomplete, particularly in terms of the potentialeffects on sensory acceptability. In this study six varieties of pitahaya, having white, pink, and red internalflesh coloration, were harvested and evaluated for sensory and quality attributes at harvest and followingstorage for two weeks at either 5 ◦C or 10 ◦C. Storage did not influence overall visual liking or color of theexternal portion of the fruit as discerned by the panelists. Alterations in the internal flesh color, such asa slight darkening, were noted to occur by instrumental measurement, but these differences were notnoticeable to the panelists. Losses in sugars and acids occurred in the flesh during storage at both storagetemperatures and were related to declines in fructose, glucose and malic acid. In contrast, antioxidantactivity was reduced by storage at 5 ◦C but was unchanged at 10 ◦C, with betacyanin concentration notdiffering from that determined at harvest. Aldehydes were the most abundant aroma volatiles detected injuice from the flesh, with storage increasing total aldehyde amount, particularly at 10 ◦C. Total alcohols, onthe other hand, were reduced by storage, the amount of reduction not dependent on storage temperature.Regardless of the storage-induced changes in the various components measured, panelists did not reportany significant differences in overall liking, flavor, sweetness, tartness or texture. There were substantialvarietal differences in sensory and quality attributes, regardless of the impact of storage. ‘Cebra’ hadvery low sweetness relative to the other varieties and had low flavor and overall liking scores. Panelistperception of flavor quality was most closely linked with varietal differences in SSC and TA, althoughthere were clear differences in aroma volatiles as well. Mexicana, a white-fleshed variety, had the lowest

antioxidant activity, corresponding to low amounts of the red betacyanin pigments. The study indicatedthat storage, and particularly that at 10 ◦C, caused a variety of measureable changes in a range of pitahayaquality parameters but that these changes did not substantially alter the sensory quality of the fruit.Further research is needed to determine whether or not varietal or storage-induced differences in aromavolatile content have an impact on pitahaya flavor.

Published by Elsevier B.V.

∗ Corresponding author.E-mail address: david.obenland@ars.usda.gov (D. Obenland).

1 To whom reprint requests should be addressed. Mention of trade names orommercial products in this publication is solely for the purpose of providing spe-ific information and does not imply recommendation or endorsement by the U.S.epartment of Agriculture. USDA is an equal opportunity provider and employer.

ttp://dx.doi.org/10.1016/j.scienta.2015.12.021304-4238/Published by Elsevier B.V.

1. Introduction

Pitahaya, pitaya or dragon fruit are general names for a diversegroup of genera of the family Cactaceae. The major genus, Hylo-cereus, has as many as 16 different species that are commerciallycultivated (Le Bellec et al., 2006). These differ in a variety of char-acteristics, one of the most notable being the color of the pulp.

Pitahaya are native to Central and South America (Ortiz-Hernándezand Carillo-Salazar, 2012) and are commercially cultivated in awide range of countries including Mexico, Nicaragua, Guatemala,United States, Taiwan, Vietnam, Philippines and Israel. The fruit

dx.doi.org/10.1016/j.scienta.2015.12.021http://www.sciencedirect.com/science/journal/03044238http://www.elsevier.com/locate/scihortihttp://crossmark.crossref.org/dialog/?doi=10.1016/j.scienta.2015.12.021&domain=pdfmailto:david.obenland@ars.usda.govdx.doi.org/10.1016/j.scienta.2015.12.021

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ave gained popularity at least in part as a result of the attractiveppearance of the flesh and due to the potential health benefits ofhe high levels of betacyanins that are characteristic of the red- orurple-colored pitahaya varieties (Stintzing et al., 2002; Wybraniecnd Mizrahi, 2002). Betacyanins, as well as polyphenols in the pita-aya flesh, have been shown to have strong antioxidant activityWu et al., 2006) and could potentially help protect against disor-ers in the body mitigated by oxidative stress.

Storage of pitahaya at temperatures above 20 ◦C leads to rapidoftening and a loss of both sugar and acidity (Punitha et al., 2010),herefore the fruit are generally stored at temperatures of 14 ◦C andelow to slow the occurrence of these changes. Nerd et al. (1999)eported that storage of Hylocereus polyrhizus from Israel for up to 2eeks at 6 ◦C and 14 ◦C effectively maintained quality, although the

ruit stored at 6 ◦C for 2 weeks became unacceptably soft upon afterransfer to 20 ◦C for a further week. The same authors found thatylocereus. undatus, however, lost flavor quality after two weekst 14 ◦C and developed chilling injury to the peel following storageor 2 weeks at 6 ◦C plus 1 week at 20 ◦C, indicating the potentialor differential species tolerance. Growing location may also affecthe response to cold temperature as H. undatus grown in Californiaithstood storage at 5 ◦C for 20 days with good external quality

nd only minor internal injury (Freitas and Mitcham, 2013). Hoat al., (2006), using H. undatus from Vietnam, stored fruit for threeeeks at 5 ◦C with almost no loss in flavor and acceptable external

uality. In an attempt to further extend the possible storage timet low temperature modified atmosphere packaging and the useerforated plastic bags have also been employed (To et al., 1999;reitas and Mitcham, 2013).

Aroma volatiles are often key components involved in the deter-ination of fruit flavor but are inadequately studied in pitahaya.

élis et al. (2012) isolated volatile components from yellow pita-aya (Selenicereus megalanthus) using steam distillation and thensed aroma extract dilution analysis (AEDA) to identify nine odor-ctive compounds that could potentially influence flavor. In thisrief paper there was no attempt to link this information to sensorynalysis to try to determine if these compounds were important toitahaya flavor. Storage of pitahaya is associated with losses in acid-

ty and firmness (Nerd et al., 1999; Nerd and Mizrahi, 1999) thatikely have a role in causing the loss in flavor quality that occurs.hanges to aroma volatiles in response to storage have been pre-iously found to be important in other fruit (Obenland et al., 2011;benland et al., 2013), but this has not been explored in pitahaya.

Pitahaya is currently produced in California on a relatively smallcale but increasing interest in the crop has led to a need to betternderstand the factors that influence its postharvest quality. Theain objectives of this study were to examine the impact of cold

torage on the sensory and quality attributes of a diverse group ofitahaya varieties from the genus Hylocereus grown in Californiand to evaluate the potential impact of aroma volatiles on differ-nces in flavor due to both variety and storage regime. Prior sensory

valuation of pitahaya had focused only on liking of flavor or exter-al appearance so it was also of particular interest to do a moreetailed examination of differences in other sensory parametershat may be influenced by storage.

Fig. 1. Varieties of pitahay

culturae 199 (2016) 15–22

2. Materials and methods

2.1. Fruit and storage treatments

Approximately 65 commercially-mature pitahaya fruit per vari-ety were harvested from experimental plots at the University ofCalifornia South Coast Research and Extension Center in Irvine, CAon September 30, 2013. The following varieties (Fig. 1) and associ-ated flesh colors were used: Cebra (C, red, H. costaricensis); Lisa (L,red, H. costaricensis); Rosa (R, red, H. costaricensis); San Ignacio (SI,red, H. costaricensis); Physical Graffiti (PG, light pink, H. polyrhizusx H. undatus); Mexicana (M, white, H. undatus). The fruit were thentransported the same day in an air-conditioned vehicle to the Uni-versity of California Kearney Agricultural Center (UCKAC) in Parlier,California, a distance of 426 km. The fruit were held overnight atambient conditions (20 ◦C). On the following day the fruit wereequally divided into three treatments lots: 1) Initial evaluation (onOctober 2, 2013) following an additional overnight storage at 20 ◦C;2) 14 d storage at 5 ◦C; 3) 14 d storage at 10 ◦C. Fruit from the twocold storage treatments were allowed to warm to ambient (20 ◦C)temperature prior to quality or sensory evaluation.

2.2. Color evaluation

Twelve fruit from each treatment were divided into four repli-cates with three fruit per replicate. Two types of color readings weretaken with a Minolta CR-400 colorimeter (Ramsey, NJ) from eachfruit using single measurements: 1) skin surface at the equator; 2)interior flesh color from a longitudinal cut at the equator.

2.3. Sample preparation

Samples were prepared by peeling one half of eachlongitudinally-cut fruit per replicate and freezing samples ofpulp while juicing the remaining tissue using a blender. Tissuefrom three fruit were pooled and utilized for each of the fourreplications. The blended pulp mixture was passed through afilter under vacuum to obtain the juice. Five mL of the resultingjuice was placed into a 12 mm × 32 mm glass headspace vial with5 mL saturated CaCl2 and 1-pentanol at a final concentration of490 �g L−1. The mixture was kept frozen at −20 ◦C until aromavolatile analysis was performed. The remainder of the juice wasfrozen at −20 ◦C in plastic vials and later used for analysis ofsoluble solids concentration (SSC) and titratable acidity (TA). Thefrozen pulp tissue was transported to the University of CaliforniaDavis (UCD) and used to assay sugars, organic acids, antioxidantactivity and betacyanins.

2.4. Sugars and acids

Soluble solids concentration (SSC) was measured using an Atago

digital refractometer (Bellevue, WA) and titratable acidity (TA) bytitration with 0.1 mol L−1 NaOH with an automatic titration sys-tem (Mettler T50A, Columbus, OH). Acidity values were expressedon a malic acid basis. Pulp samples (10 g) for sugar and organic

a used in this study.

D. Obenland et al. / Scientia Horticulturae 199 (2016) 15–22 17

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ig. 2. Color of the interior flesh in terms of lightness (L), chroma (C) and hue angleP ≤ 0.05) differences among storage conditions within variety are indicated by diff

cid determination were mixed with 20 mL ultrapure water andhoroughly mixed for 1 min. The diluted samples were then cen-rifuged at 3500 rpm for 3 min and the supernatant removed andubjected to an additional 10 min centrifugation at 14,000 rpm. Theupernatant (200 �L) was diluted with 1800 �L ultrapure water,assed through a C18 Sep-Pak and a 0.45 �m filter and then used fornalysis of soluble sugars and organic acids. Sugars were analyzedsing a HPLC equipped with a 300 mm × 7.8 mm Aminex HPX-87Column (Bio-Rad, Hercules, CA) and a ELSD detector at 40 ◦C. Theobile phase was deionized water and the flow rate 0.01 mL s−1

ith a column temperature of 80 ◦C. Quantification was done byhe use of glucose and fructose standard curves. Organic acidsere analyzed using a HPLC with a UV detector at 210 nm and a

00 mm × 7.8 mm Aminex HPX-87H column (Bio-Rad) maintainedt 50 ◦C. The mobile phase was 0.01 mol L−1 sulfuric acid and theow rate 0.01 mL s−1. Quantification was done by the use of stan-ard curves generated for oxalic, citric and malic acids. Analysesor both sugar and acids were replicated four times using separateruit samples.

.5. Antioxidant activity and betacyanins

Preparation of an extract for measurement of antioxidant activ-ty was initiated by adding 25 mL of methanol to 10 g pulp sample

nd homogenizing the mixture for 1 min, followed by centrifuga-ion at 3500 rpm for 3 min. The supernatant was then centrifugedt 14,000 rpm for 10 min at 4 ◦C. From the final supernatant 50 �Las removed and added to 4 mL ferric reducing antioxidant power

influenced by storage for two weeks at either 5 ◦C or 10 ◦C. Statistically significantletters.

(FRAP) solution. The mixture was vortexed and then incubated for30 min in a 37 ◦C water bath. Antioxidant activity was quantified bymeasuring the absorbance of the solution at 593 nm and compar-ison to standard curves. The assay for betacyanin was based uponthe methods of Phebe et al., (2009) with some modifications. Teng of pulp was combined with 20 mL 80% ethanol and homogenizedfor 1 min and then the mixture centrifuged at 3500 rpm for 5 min.The pellet was re-extracted in the same manner two more timeswith 10 mL 80% ethanol and all supernatants were combined. Thecombined supernatants were made up to 50 mL with water and theabsorbance measured at 538 nm with a spectrophotometer. Beta-cyanin concentration was determined by the following formula:mg g−1 = A538 × (MW) × V × DF × 100/(ε × L × W); where A538 is theabsorbance at 538 nm, MW the molecular weight of betacyanin(550), V the volume of the extract in mL, DF the dilution factor, ε themean molar absorptivity, L the path length (1 cm), and W the freshweight of the material being extracted. Analyses for both antiox-idant activity and betacyanins were replicated four times usingseparate fruit samples.

2.6. Aroma volatiles

Volatile juice samples in headspace vials were thawed and thevials placed into a cooled 4 ◦C rack to maintain the samples prior to

analysis. Aroma volatile measurement was performed using solidphase microextraction (SPME) aided by a Gerstel MPS-2 roboticsystem (Linthicum, MD, USA). Trapping of the volatiles utilized75-�m carboxen/polydimethylsiloxane fibers (Supelco, St. Louis,

18 D. Obenland et al. / Scientia Horticulturae 199 (2016) 15–22

Table 1Concentrations of sugars and acids in six varieties of pitahayas evaluated at harvest or following two weeks of storage at either 5 ◦C or 10 ◦C.

SSCa Sugars (g kg−1) TAa Organic acids (g kg−1)

Variety (10g kg−1) Fructose Glucose Total (10g kg−1) Oxalic Citric Malic Total

Cebra 10.89b 41.07b 53.50c 94.57ab 0.51a 0.09b 0.20a 10.06a 10.35aRosa 11.78b 40.80b 52.79c 93.60ab 0.47a 0.10b 0.03c 9.56ab 9.69abLisa 11.38b 37.39b 50.13c 87.52b 0.51a 0.07b 0.21a 9.62ab 9.91abSan Ignacio 12.27ab 39.80b 49.64c 89.44b 0.30b 0.15a 0.15ab 8.41ab 8.71abMexicana 13.29a 48.22a 70.06a 118.27a 0.16c 0.16a 0.09bc 8.52ab 8.77abPhysical Graffiti 12.17ab 41.09b 58.88b 99.97b 0.32b 0.07b 0.06c 8.21b 8.33bStorageNone 12.21a 45.49a 58.84a 104.33a 0.44a 0.11a 0.13a 10.44a 10.68a2 weeks 5 ◦C 12.29a 41.17b 54.33b 95.50b 0.43a 0.09a 0.11a 9.30b 9.51b2 weeks 10 ◦C 11.39b 37.52c 54.34b 91.86b 0.26b 0.11a 0.13a 7.44c 7.68cSourceb

Variety (V) * * * * * * * * *Storage (S) * * * * * NS NS * *V*S NS NS * NS * * NS NS NS

Statistically significant (P ≤ 0.05) differences among varieties or storage conditions are indicated by values being followed by different letters.

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Table 2Aroma volatiles identified in pitahayas that differed in concentration due to eithervariety or storage.

Aroma volatile Abbreviation Descriptor

AldehydesAcetaldehyde Aa Pungent, solventyButanal But Fruity, green, bananaPentanal Pen Green, grassy, nuttyHexanal Hex Fresh, greenE-2-hexenal EHex Green, bananaHeptanal Hep Green, herbalOctanal Oct Fatty, citrusNonanal Non Citrus, floral, greenDecanal Dec Waxy, citrus,floral

Hydrocarbonsp-Cymene pCym Solvent, citrusLimonene Lim Citrus, freshDodecane Dod AlkaneTridecane Tdec Alkane

AlcoholsEthanol EtOH EthanolLinalool Lin Citrus, floralHexanol Hex Green, fruity

OtherMethyl heptenone Mhep Citrus, green, appleButyl butanoate Bbut Fruity, banana,2-Pentyl furan 2Pfur Fruity, green, earthy

a

a SSC:soluble solids concentration, TA: titratable acidity.b Asterisk indicates statistical significance (P ≤ 0.05) while NS indicates a lack of s

O, USA). Chromatographic runs and analyte quantification wereerformed using an Agilent 7980 gas chromatograph (Agilent,alo Alto, CA) paired with an Agilent 5975 mass spectrometer.etails of the hardware used and both trapping and chromato-raphic protocols are as previously described (Obenland et al.,008; Obenland et al., 2013) except that only the mass spectrome-er was used for quantification in this study. In addition to utilizing

iley/NBS library spectra, peak identification was performed byomparison of compound retention indices to published values.emi-quantification of the peaks was conducted by comparison ofeak areas to a standard curve generated in pitahaya juice using 3-ethyl butanal with the resulting concentrations being expressed

s 3-methyl butanal equivalents. Variability between the runs wasompensated for by comparison of 1-pentanol internal standardalues and appropriately adjusting the analyte values. Volatile anal-ses were replicated four times with each replicate being a separateruit sample.

.7. Sensory evaluation

Sensory evaluation was conducted at UCKAC in the Sensoryesting Facility. After equilibration to ambient temperature (20 ◦C)he fruit were then washed and allowed to dry. Fruit used for theisual assessment were selected based upon uniformity of sizend external characteristics across the six varieties. Panelists wereeated in individual booths illuminated with daylight spectrumight. Panelists were employees of UCKAC and had extensive expe-ience with sensory evaluation of fruit but not with pitahaya. In theonth prior to initiating sensory testing a roundtable discussionas conducted and samples of various pitahaya varieties examined

o provide a baseline on what should be evaluated and to develophe proper vocabulary. Further instruction was provided on theays of actual sensory testing. Approximately 12–15 panelists werevailable each day for the sensory evaluations. For visual assess-ent whole or longitudinally-cut fruit were placed onto white

lastic plates that had been labeled with random three-digit num-ers. Samples were placed in random order so that each panelisteceived the set of samples in a different order. Panelists evaluatedhole and cut fruit with 9-point hedonic ratings for both overall

ppearance and color where 1 = extremely dislike, 5 = neither like

or dislike, and 9 = extremely like. For flavor assessment the topnd bottom one-third of the fruit was removed and not utilized foresting in order to lessen variability among the samples. The centerhird of each fruit was cut into slices approximately 1.3 cm thick

Aroma descriptors from the University of Florida Citrus Flavor and ColorDatabase (http://www.crec.ifas.ufl.edu/rouseff/) and the Good Scents Company(http%3A%2F%2Fthe+goodscentscompany.com%2Findex.html).

and then cut into six equal size pieces. Eight pooled fruit were usedfor each variety and treatment. One piece of each was served in awhite 30-mL soufflé cup labeled with a unique three-digit number.Samples were presented in random order to each panelist. Prior tothe initial tasting and between samples panelists were instructed torinse their mouths with water to cleanse the palate. Panelists scoredthe fruit for overall liking, flavor, sweetness, tartness and flesh tex-ture using the same 9-point hedonic scoring system as outlined forvisual evaluations.

2.8. Statistical analysis

Quality and sensory data were analyzed with SPSS (Chicago, IL,USA) using a general linear model with variety and storage beingfixed effects. Mean comparisons among varieties and storage timeswere determined using Tukey’s test at the 0.05 level of significance.

http://www.crec.ifas.ufl.edu/rouseff/http://www.crec.ifas.ufl.edu/rouseff/http://www.crec.ifas.ufl.edu/rouseff/http://www.crec.ifas.ufl.edu/rouseff/http://www.crec.ifas.ufl.edu/rouseff/http://www.crec.ifas.ufl.edu/rouseff/http://www.crec.ifas.ufl.edu/rouseff/http://www.crec.ifas.ufl.edu/rouseff/http://http:%2F%2Fthe+goodscentscompany.com%2Findex.htmlhttp://http:%2F%2Fthe+goodscentscompany.com%2Findex.htmlhttp://http:%2F%2Fthe+goodscentscompany.com%2Findex.html

D. Obenland et al. / Scientia Horticulturae 199 (2016) 15–22 19

Table 3Aroma volatile concentrations in six varieties of pitahayas immediately after harvest or following two weeks at either 5 ◦C or 10 ◦C. The varieties examined were: Cebra (C),Rosa (R), Lisa (L), San Ignacio (SI), Mexicana (M), and Physical Graffiti (PG). Identities of the volatile abbreviations are as listed in Table 2. Semi-quantified values shown aremethyl butanal equivalents in �g L−1.

Aldehydes Hydrocarbons Alcohols Other volatiles

Aa But Pen Hex EHex Hep Oct Non Dec pCym Lim Dod Tdec EtOH Lin Hex Mhep Bbut 2Pfur

VarietyC 82ab 19b 69c 6865b 18b 61b 82b 108b 33a 26ab 177a 37a 217b 67a 16b 203b 43a 58a 174abR 96a 28ab 372abc 12475ab 31ab 132b 140b 134b 42a 34a 158a 51a 191b 104a 49a 233ab 50a 65a 233aL 94a 30a 513ab 17198a 46a 149ab 151b 118b 39a 30ab 160a 49a 263b 87a 23b 193b 60a 66a 254aSI 64b 20b 187bc 10475ab 20b 76b 92b 92b 26a 25ab 100a 35a 189b 67a 40ab 432b 36a 71a 115bcM 58b 28ab 530ab 7727b 29ab 317a 554a 285a 19a 22b 150a 46a 164b 135a 16b 811a 48a 22b 78cPG 78b 21b 232abc 7865b 15b 113b 146b 115b 26a 24b 108a 55a 596a 82a 39ab 327ab 36a 25b 95bcStorageNone 102a 22b 246b 4559c 17b 164ab 291a 195a 19c 27a 90b 54a 313a 115a 33a 509a 36b 19b 157ab5 ◦C 72b 18b 83b 8941b 22b 70b 102b 88b 43a 26a 154ab 43ab 260a 95ab 35a 219c 37b 63a 128b10 ◦C 62b 33a 622a 17802a 41a 190a 190ab 143ab 31b 28a 182a 40b 236a 61b 24a 372b 63a 73a 189aSourcea

Variety * * * * * * * * * * NS NS * NS * * NS * *Storage * * * * * * * * * NS * * NS * NS * * * *

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. Results

Changes in skin color due to storage were relatively minor, withhroma slightly increasing for PG at 10 ◦C and hue angle decreas-ng during cold storage for SI (5 ◦C and 10 ◦C) and C (10 ◦C) (dataot shown). Storage-induced changes in flesh color were, however,ore pronounced (Fig. 2). In four of the six varieties L declined, this

eing especially prominent at 10 ◦C, indicating a slight darkeningn color due to this storage treatment. An increase in chroma wasbserved in M stored at 10 ◦C, whereas increases were seen in SI5 ◦C and 10 ◦C) and PG (5 ◦C). In all but two varieties hue angleecreased during cold storage, most commonly at 10 ◦C and with

arge changes being observed for M, the white fleshed variety.Mexicana had the highest SSC, although the amount was not

tatistically-different from SI and PG (Table 1). This was alsoeflected in M having considerably greater amounts of both fruc-ose and glucose in comparison to the other varieties which, exceptn the case of PG, were very similar to each other in the amountsf these two sugars. Titratable acidity differed among the varieties,ith C, R and L having the highest TA values, S and P having lesser

oncentrations, and M with the lowest TA (Table 1). Differences inhe individual organic acids between the varieties did not clearly

irror what was observed for TA. In the case of malic acid, the over-helmingly dominant organic acid, the only significant differences

bserved were between C and PG. For oxalic acid SI and M had theighest amounts, while C and L had the highest concentration ofitric acid in comparison to the other varieties. Storage for 2 weekst 5 ◦C did not alter SSC, while there was a slight reduction dueo storage at 10 ◦C. A decline in fructose occurred at both storageemperatures, with the loss at10 ◦C greater than 5 ◦C. In the casef glucose, there was also a storage-induced decline in amount,lthough there was no difference in response due to temperature.imilarly to SSC, TA declined in storage at 10 ◦C but not at 5 ◦C. Bothxalic and citric acids were unchanged by storage but malic acidoncentration declined during storage, with 10 ◦C storage exhibit-ng the largest loss in TA.

The antioxidant activity for M was noteworthy in that it wasore than two-fold lower than the other varieties (Fig. 3). The other

ve varieties were similar to each other, although C had slightlyigher activities than R, S or PG. Mexicana, a white-fleshed variety,

ot unexpectedly, had very low levels of red-pigmented beta-yanins as did PG, the pink-fleshed variety. Of those varieties withed flesh, SI had a slightly higher concentration of betacyanins thatid C, R or L. There was poor correspondence between betacyanin

* NS * NS * NS * * * *

ndicated by values being followed by different letters.cance.

concentration and antioxidant activity as PG had low amounts ofbetacyanins and yet had fairly high overall antioxidant activity.Storage for 2 weeks at 5 ◦C slightly reduced the antioxidant activity,while storage for 2 weeks at 10 ◦C did not change it. There was noeffect of storage duration on the betacyanin concentration.

A total of 34 aroma volatiles were identified in the pitahaya juicesamples (data not shown). Of these compounds 19 were found tohave significant differences due to either variety or storage treat-ment and are shown in Table 2 along with characteristic descriptorsof each volatile. Aldehydes were by far the most abundant volatilesidentified, representing on average 90% of the total amount, withvarious hydrocarbons, alcohols, a ketone, an ester and a furan mak-ing up the rest of the identified volatiles (Table 3, Fig. 4). There werelarge varietal differences in total aldehydes with L having at leastdouble the concentration present in C, M or PG (Fig. 4). By far themost abundant compound was hexanal which accounted for 92% ofthe total amount of this chemical class. Varietal differences in indi-vidual aldehydes generally followed the trend for total aldehydeswith the exceptions of octanal and nonanal that had significantlyhigher amounts in M as compared to L. For the hydrocarbon class ofcompounds the only sizable varietal difference was the significantlygreater amount of tridecane in PG as compared to the other vari-eties, resulting in a greater level of total hydrocarbons. Mexicanawas significantly higher in total alcohols that the other varieties,primarily due to the greater amount of hexanol present in the fleshof this variety. The ester, butyl butanoate, was more abundant in C,R, L, and SI than in M and PG and 2-pentyl furan was present to ahigher degree in R and L than in the rest of the varieties.

Storage enhanced total aldehyde concentration with fruit storedat 10 ◦C having a greater concentration than that stored at 5 ◦C(Fig. 4), this being primarily due to increases in hexanal (Table 3).There was no trend in overall hydrocarbon levels as a result ofstorage, although limonene increased and dodecane decreased inamount relative to fruit that had not been stored. Alcohols declinedin amount during storage driven by losses in both ethanol (5 ◦C) andhexanol (5 ◦C and 10 ◦C). Methyl heptenone, butyl butanoate and2-pentyl furan all were present in greater concentrations in fruitstored for 2 weeks at 10 ◦C relative to no storage or storage for 2weeks at 5 ◦C. Butyl butanoate was also enhanced in concentrationby storage at 5 ◦C compared to fruit that were not stored.

In terms of eating quality overall liking of R and SI was superiorto that of C (Table 4). This was largely a result of the relatively poorflavor of C, although only SI had flavor that was statistically better.A low perception of the sweetness of C relative to all of the other

20 D. Obenland et al. / Scientia Horticulturae 199 (2016) 15–22

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arieties likely played a major role in the poor degree of liking of itsavor. Tartness and texture, on the other hand, did not differ amonghe varieties. Additionally, there were no significant differences inny parameters related to eating quality due to storage treatmentTable 4). Panelists liked the external appearance of L better thanI, which was itself preferred to PG (data not shown). Color was theominant factor involved as ratings for color among the varietiesere closely related to those of overall liking (data not shown).

torage had no impact on external overall liking or color. Internalppearance, judged from sectioned halves of the fruit, did not dif-er among the varieties or storage treatments for overall likability,lthough panelists liked the color of C, L or R better than that of PGdata not shown). Storage did not alter the color perceived by theanelists.

. Discussion

A number of prior studies have been conducted to examine theffects of storage on pitahaya and have provided recommendations

st or following storage for two weeks at either 5 ◦C or 10 ◦C. Statistically significantent letters, antioxidant activity is capitalized.

regarding the optimal storage conditions and times to ensure thatquality is maintained (Nerd et al., 1999; Nerd and Mizrahi, 1999;Hoa et al., 2006; Corrales-García and Canche-Canche, 2008; Punithaet al., 2010; Freitas and Mitcham, 2013). Information on the fullimpact of storage on the fruit has, however, been somewhat limitedas, to the best of our knowledge, there had never previously been astudy which performed a full sensory panel evaluation comparingpitahaya following different storage protocols. In this research weconducted a comprehensive assessment of the impact of storageon six pitahaya varieties grown in California, including evaluationof standard quality parameters, antioxidant status, aroma volatileprofile and sensory quality.

Sensory panelists judged there to be no differences in eitheroverall external liking or color due to storage, in accordancewith the relatively small differences found in colorimeter read-

ings among the storage regimes for the different varieties (datanot shown). Others have also found no loss in pitahaya externalvisual quality during 14 days of storage at temperatures from 10 ◦Cto 14 ◦C (Nerd et al., 1999; Nerd and Mizrahi, 1999) but the devel-

D. Obenland et al. / Scientia Horti

Table 4Sensory quality of six varieties of pitahayas immediately after harvest or following2 weeks of storage at either 5 ◦C or 10 ◦C.

Overall likinga Flavora Sweetnessa Tartnessa Texturea

VarietyCebra 6.1b 5.9b 5.1b 6.5a 5.7aRosa 7.2a 7.0ab 6.5a 7.2a 6.6aLisa 6.7ab 6.8ab 6.4a 6.6a 6.1aSan Ignacio 7.4a 7.3a 7.1a 7.1a 6.3aMexicana 6.5ab 6.3ab 6.4a 6.5a 5.5aPhysical Graffiti 6.3ab 6.2ab 6.4a 6.3a 5.9aStorageNone 7.0a 6.9a 6.4a 7.0a 6.1a2 weeks 5 ◦C 6.6a 6.5a 6.2a 6.7a 6.2a2 weeks 10 ◦C 6.4a 6.4a 6.2a 6.4a 5.8aSourceb

Variety (V) * * * NS NSStorage (S) NS NS NS NS NSV*S NS NS NS NS NS

Statistically significant (P ≤ 0.05) differences among varieties or storage conditionsare indicated by values being followed by different letters.

a Sensory scores on a 9-point scale where 1:extremely dislike, 5:neither like nordislike, and 9:extremely like.

b Asterisk indicates statistical significance (P ≤ 0.05) while NS indicates a lack ofsignificance.

Fig. 4. Differences within classes of aroma volatiles in six pitahaya varieties at harvest (P ≤ 0.05) differences among varieties or storage conditions are indicated by different lett

culturae 199 (2016) 15–22 21

opment of brown surface lesions can occur at lower temperaturesof 4 ◦C to 8 ◦C that indicates the development of chilling injury(Corrales-García and Canche-Canche, 2008). Frietas and Mitcham(2013) reported that storage at 5 ◦C was superior to either 7 ◦C or10 ◦C for maintaining pitahaya visual appearance. In that study thefruit were held for an additional 5 days at 20 ◦C following cold stor-age whereas in this test the time was less than 24 h. It is possible thatdifferences in external appearance would have been more markedin our test had the time at 20 ◦C been extended. Low tempera-ture injury is also manifested in pitahaya by regions of the interiorflesh that become somewhat translucent and have a darkenedappearance (Corrales-García and Canche-Canche, 2008; Freitas andMitcham, 2013). Although sensory evaluation performed in thisstudy did not reveal any differences in the internal appearance ofthe fruit among the storage regimes (data not shown), colorimeterreadings did indicate an effect of storage on internal flesh color,although it apparently was not noticeable to the panelists, even inthe case of M where there was substantial change in hue angle.

Flavor evaluations indicated that cold storage at either 5 ◦C or

10 ◦C did not influence the overall liking of the fruit, this conclu-sion being accompanied by the panelists being unable to identifyany differences in flavor, sweetness, tartness or texture as a result

or following storage for two weeks at either 5 ◦C or 10 ◦C. Statistically significanters.

2 Horti

odihfcw(bTanwflo

dvCaSattdRflpb

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pitcptctoeitetoflatii

Proc. 100, 101–114.Wu, L.-C., Hsu, H.-W., Chen, Y.-C., Chiu, C.-C., Lin, Y.-I., Ho, J.-a.A., 2006. Antioxidant

and antiproliferative activities of red pitaya. Food Chem 95, 319–327.Wybraniec, S., Mizrahi, Y., 2002. Fruit flesh betacyanin pigments in Hylocereus

cacti. J. Agric. Food Chem. 50, 6086–6089.

2 D. Obenland et al. / Scientia

f storage (Table 4). Apparently the losses in sugar and largerecreases in acid that occurred during cold storage (Table 1) were

nsufficient to influence any of the sensory parameters. This mayave been a consequence of the high SSC/TA ratio present in the

ruit at harvest (average across varieties of 27.8) making any furtherhanges difficult to detect in the already low-acid fruit. Changesere observed in aroma volatile concentration due to storage

Table 3), primarily an increase in aldehydes and loss in alcohols,ut these also did not impact the overall liking or flavor of the fruit.hese results, indicating a lack of impact of cold storage on flavor,re in agreement with those of Nerd et al. (1999) who reportedo loss of flavor for either H. undatus or H. polyrhizus after up to 3eeks at 6 ◦C. The authors also noted, however, a rapid decline inavor quality during storage at higher temperatures of either 14 ◦Cr 20 ◦C.

While not influenced by cold storage, there were significantifferences in sensory attributes present among the six pitahayaarieties, most notable being a greater liking for R and SI than for C.losely linked to the lesser liking was a reduced sweetness in C rel-tive to the other two varieties and a poorer flavor in comparison toI. The reason for the lack of sweetness is, however, unclear as therere no obvious differences in either sugars or acids to account forhis (Table 1). There is also no evidence that volatiles contributedo the dissimilarity in liking as there were no consistent significantifferences among the individual volatile components between C,, and SI (Table 3). Published sensory analyses of pitahaya varietalavor are not readily available and we were unable to find any otherrior instances in the literature that attempted to understand theasis of varietal differences.

To date, Célis et al., (2012) is the only published study thatescribes the volatiles present in pitahaya. These authors identified

total of 121 volatiles in samples of yellow pitahaya (Selenicereusegalanthus) with the sample composition consisting of terpenes,

lcohols, parafins, esters, acids, ketones and other miscellaneousompounds. Although many of the same volatiles were identi-ed in the two studies, aldehydes were more predominant in thistudy, constituting more than 90% of the total volatile amount. Thisifference in reported composition could have been both due toifferences in the pitahaya tissue analyzed and to the methodssed for extraction. Célis and co-workers utilized solvent extractionnd subsequent concentration, while SPME, a headspace analyticalechnique, was used in this study. Although volatile compositionn this study substantially varied due to both storage conditionsnd variety the differences could not be definitively linked to anyifference in flavor.

Given that there has been substantial attention devoted to theotential health benefits conferred by the red betacyanin pigments

n pitahaya (Wu et al., 2006; Tenore et al., 2012), it was of interesto examine both the effects of cold storage and variety on beta-yanin content and overall antioxidant activity provided by theseigments and other components in the flesh. Unsurprisingly, M,he white-fleshed variety, had little or no betacyanin content andorresponding low antioxidant activity (Fig. 3). Physical Graffiti,he pink-fleshed variety, on the other hand, also had low amountsf betacyanins but had much higher antioxidant activity that wasquivalent to that of all of the red-fleshed varieties except C. Thenability of the greater amount of betacyanin in the red varietieso provide additional antioxidant activity may indicate the influ-nce of other active components in PG. Wu et al., (2006) reportedhat although extract fractions from red pitahaya composed mainlyf betacyanins had the highest antioxidant activity, fractions withavonoids and phenolics were also present that had substantial

ctivity. Betacyanin content in the current study did not differ dueo storage duration, although a slight reduction in antioxidant activ-ty occurred at 5 ◦C but not 10 ◦C. The stability of betacyanin contentn cold storage had been previously shown (Ortiz-Hernández and

culturae 199 (2016) 15–22

Carillo-Salazar, 2012), although this was following the applicationof 1-methylcyclopropene at harvest.

In summary, cold storage of pitahayas for two weeks at either5 ◦C or 10 ◦C caused a loss in sugars and organic acids, accompaniedby a shift in the quantities of aroma volatiles present. Regardless ofthese changes in composition, however, panelists were unable todifferentiate the flavor of stored fruit from that freshly harvestedin terms of liking, overall flavor, sweetness, tartness or texture.Betacyanin content and antioxidant activity were also relativelyinsensitive to storage as was exterior color and appearance. Differ-ences in flavor liking noted by panelists were variety-based withthe strongest liking being associated with high overall flavor ratingsand high sweetness. Aroma volatile concentrations also differed byvariety but more research is needed to determine what influencethese compounds have on pitahaya flavor.

Acknowledgement

Thanks to Paul Neipp for his assistance with aroma volatile andfruit quality analysis.

References

Célis, C.Q., Gil, D.E., Pino, J.A., 2012. Characterization of odor-active compounds inyellow pitaya (Hylocereus megalanthus (Haw.) Britton et Rose). Revista CENICCiencias Químicas 43, 1–6.

Corrales-García, J., Canche-Canche, E., 2008. Physical and physiological changes inlow-temperature-stored pitahaya fruit (Hylocereus undatus). J. Prof. Assoc.Cactus 10, 108–119.

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Impact of storage conditions and variety on quality attributes and aroma volatiles of pitahaya (Hylocereus spp.)1 Introduction2 Materials and methods2.1 Fruit and storage treatments2.2 Color evaluation2.3 Sample preparation2.4 Sugars and acids2.5 Antioxidant activity and betacyanins2.6 Aroma volatiles2.7 Sensory evaluation2.8 Statistical analysis

3 Results4 DiscussionAcknowledgementReferences