Does ethylene degreening affect internal quality of citrus fruit?

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  • Postharvest Biology and Technology 62 (2011) 5058

    Contents lists available at ScienceDirect

    Postharvest Biology and Technology

    journa l homepage: www.e lsev ier .com/ l

    Does e ty

    Lina May Poa Department o 50250b Vegetable and ty, Co

    a r t i c l

    Article history:Received 14 MAccepted 16 A

    Keywords:CitrusDegreeningEthyleneFlavorNutritional qu

    ver, eted pon ofnternethyleel orabreaeningnts adegrebility

    partially, to storage of the fruit for 5 days at 20 C. Nevertheless, ethylene degreening did not enhanceoff-avor perception or accumulation of off-avor volatiles, nor had any effect on levels of health pro-moting compounds such as vitamin C, total phenols and avonoids, or antioxidant-activity of citrus juice.We conclude that although ethylene affects peel color break, it is probably not involved in regulation ofinternal ripening processes in citrus fruit and, therefore, does not impair internal fruit quality.

    2011 Elsevier B.V. All rights reserved.

    1. Introdu

    In climaphysiologicing, includiacids, aromGiovanoni,their naturand ethylenexogenousrelated propigments anpeel tissueand Barmothese obserfruit to eth2030 C wand to rendNewhall, 19ing treatme

    CorresponE-mail add

    0925-5214/$ doi:10.1016/j.ction

    cteric fruit, ethylene plays a key role in governingal and biochemical changes that occur during ripen-ng color break, softening, and accumulation of sugars,a volatiles, vitamins, etc. (Lelievre et al., 1997; Barry and2007). In contrast, citrus fruit are non-climacteric, i.e.,al ripening is not accompanied by rises in respiratione production rates (Eaks, 1970). However, exposure toethylene has been shown to stimulate various ripening-cesses, such as destruction of the green chlorophylld accumulation of orange/yellow carotenoids, in citrus(Stewart and Wheaton, 1972; Barmore, 1975; Purvisre, 1981; Rodrigo and Zacarias, 2007). In the light ofvations, degreening practices involving exposure of theylene at concentrations of 25L L1 for about 72h atere developed, in order to accelerate peel color changeer the fruitmore acceptable formarketing (Grierson and60; Cohen, 1978). In particular, commercial degreen-nts are especially important for early varieties, in order

    ding author. Tel.: +972 3 9683617; fax: +972 3 9683622.ress: rporat@volcani.agri.gov.il (R. Porat).

    to extend their marketing seasons, and for fruit grown in warm,tropical climates, such as those in Florida or India, where natu-ral color development is relatively weak (Wardowsky et al., 2006;Porat, 2008).

    Nevertheless, despite widespread knowledge of the effect ofethylene on peel color development, it is not yet known whetherexogenous ethylene regulates other biochemical changes associ-ated with internal ripening of citrus fruit, as it does in climactericfruit (Goldschmidt, 1998). The commondogma is that, in contrast toits effects on peel color change, ethylene has only relatively minoreffects on ripening processes in citrus esh, but this has neveryet been examined systematically. On the contrary, several linesof evidence suggest that ethylene may regulate various processesrelated to internal ripening. First, it is well known that exposureto ethylene accelerates respiration and ethylene-production ratesof citrus fruit, and these rates are indicators of activation of bio-chemical changes, such as breakdownof sugars and acids that serveas respiratory substrates (Aharoni, 1968; Vines et al., 1968; Eaks,1970). Second, previous studies have shown that ethylenedegreen-ing affects variousmetabolic pathways in citrus esh. For example,ethylene degreening decreased acidity levels in Mosambi oranges(LadaniyaandSingh, 2001), increasedproductionof aromavolatilesin green lemons (Norman and Craft, 1968), and slightly affectedaccumulation and composition of carotenoid pigments in the esh

    see front matter 2011 Elsevier B.V. All rights reserved.postharvbio.2011.04.005thylene degreening affect internal quali

    uonia, Zipora Tietela, Bhimanagouda S. Patil b, Ronf Postharvest Science of Fresh Produce, ARO, the Volcani Center, P.O. Box 6, Bet-DaganFruit Improvement Center, Department of Horticultural Sciences, Texas A&M Universi

    e i n f o

    arch 2011pril 2011

    ality

    a b s t r a c t

    Citrus fruit are non-climacteric. Howeing, stimulates various ripening-relachlorophyll pigments and accumulatiwhether exogenous ethylene affects iwe examined the possible effects ofof various citrus fruit, including Navsure to ethylene enhanced peel colorfruit tested. However, ethylene degreand had only minor effects on conteanalysis tests revealed that ethylenemarginally impaired sensory acceptaocate /postharvbio

    of citrus fruit?

    rata,

    , Israelllege Station, TX 77845, USA

    xposure to exogenous ethylene, e.g., during ethylene degreen-rocesses in the peel tissue, such as destruction of the greenorange/yellow carotenoids. Nonetheless, it is not yet knownal ripening processes in citrus esh. To address this question,ne on taste, aroma, perceived avor, and nutritional qualitynges, Star Ruby grapefruit and Satsuma mandarins. Expo-k, and respiration and ethylene production rates in all citrushad no effect on juice total soluble solids and acid contents,

    nd composition of juice aroma volatiles. Moreover, sensoryening did not affect the avor of oranges and grapefruit, butof mandarins; the latter change could be attributed, at least

  • L. Mayuoni et al. / Postharvest Biology and Technology 62 (2011) 5058 51

    of Satsuma mandarins (Matsumoto et al., 2009). Third, it has beenreported that presence of ethylene in storage rooms results inloss of desired avor, and enhanced accumulation of off-avorsin oranges, whereas removal of ethylene from storage roomsimproves oet al., 1992)of 661 transfactor of at48h,whichmetabolic a

    In summvisual appeious adversit increasesand acceler1985; Carvaon whetheinuenced bestimated d

    Over theglobal martional beneare attachinquality of forder to evregulation ocitrus fruit,degreeningvor, and nuRuby grapethat ethyleripening prfruit quality

    2. Materia

    2.1. Plant m

    Navel ofruit (Citruscv. Miho)wSeptembersons. In allcolor breakthe packingvarietiesweMama.

    2.2. Ethylen

    Fruit weinto two lotlene for 24,them in 250amounts oftration of 4chromatogrushed dailnot exceedat 20 C, bu

    2.3. Juice socontents

    Total solwith aMod

    aciditypercentagesweremeasuredby titration topH8.3with0.1MNaOH by means of a Model CH-9101 automatic titrator (Metrohm,Herisau, Switzerland). Each measurement comprised ve replica-tions, eachusing juice collected fromthreedifferent fruit, i.e., a total

    ruit porbicby tmi eringcorbsed a

    nsor

    it senexponts weatmferenof10t assnstrry stanceof rere

    f 15nsorre mrins

    alys

    ma ving tendebit eglassilutels wma v, eacher timupleere ancubes wexlbenzco, Bls hin atlo Al5mogran1,temLm

    or (Aat 7.7ctronc peaompologyof

    nearverall fruit quality (McGlasson and Eaks, 1972; Testoni. Fourth, we recently found that the expression patternscripts in mandarin esh were signicantly altered by aleast 3, following exposure to ethylene at 4L L1 forsuggests that this exposuremight have affected variousnd adaptation processes (Mayuoni et al., 2011).ary, notwithstanding its advantages in improving fruitarance, the ethylene degreening process also has var-e effects on fruit quality and postharvest storability:susceptibility to stem-end rots, enhances weight loss,ates rind and calyx senescence (Barmore and Brown,lho et al., 2008; Porat, 2008). Therefore, the decision

    r or not to degreen citrus fruit is not simple, and isy various circumstances, such as market demands andurations of storage and shelf life (Pool and Gray, 2002).last few years, because of increased competition in

    kets and increasing public awareness of the nutri-ts of horticultural produce, growers and consumersg increasing importance to the avor and nutritional

    ruit and vegetables (Kader, 2008; Patil et al., 2009). Inaluate the possible effects of ethylene degreening onf the internal ripening processes and on the quality ofwehave systematically examined theeffectsof ethyleneon taste, composition of aroma volatiles, perceived a-tritional quality of the citrus fruit Navel oranges, Starfruit, and Satsuma mandarins. Overall, we concludene is probably not involved in regulation of internalocesses in citrus and, therefore does not impair internal.

    ls and methods

    aterial

    ranges (Citrus sinensis [L]. Osbeck), Star Ruby grape-paradisi Macf.), and Satsuma mandarins (Citrus unshiuere purchased fromcommercial packinghouses during

    through November of the 2009 and 2010 growing sea-cases, fruit were harvested at the beginning of natural, and were collected directly from the harvest bins athouse. For taste score evaluations, additional mandarinre also tested, including Michal, Odem, Or, Mor, and

    e degreening

    re selected for uniformity of size and color, and divideds, which were exposed, respectively, to air or to ethy-48, or 72h. They were exposed to ethylene by placing-L airtight sealed plastic tanks, into which appropriatepure ethylene were injected, to achieve a nal concen-L L1. Ethylene concentrations were veried by gasaphy according to Porat et al. (1999). The tanks werey to ensure that accumulated carbon dioxide levels did0.2%. Control fruit were held in the same storage roomt without ethylene.

    luble solids, titratable acidity, and ascorbic acid

    uble solids (TSS) content in the juice was determinedel PAL-1 digital refractometer (Atago, Tokyo, Japan), and

    of 15 fAsc

    minedto Hirocompa0.1% asexpres

    2.4. Se

    FrudaysofsegmeEach trve difsistingpanelisto an uand veas distmeanselists wscale oThe sehere amanda

    2.5. An

    Aroaccordand blto inhi10mLMO), dThe via

    Aromentsfruit p(GC) copleswwere iVolatilStable-diviny(Supelthe viafor 5mlent, PaID, 0.2was pr5 Cmiat thatat 0.8mdetectto 206the elegraphieach cTechnocationtheir lier measurement.acid (vitamin C) contents in citrus juice were deter-

    itration with 2,6-dichlorophenolindophenol accordingt al. (1980). Ascorbic acid levels were determined bythe titration volumes of citrus juices with those ofic acid (SigmaAldrich, St. Louis, MO), and results ares milligrams of ascorbic acid per 100mL of juice.

    y evaluations

    sory qualitywas tested on the day of harvest and after 5sure toair or ethylene. Fruitwerepeeled, and separatedere cut into halves and placed into covered glass cups.ent included a mixture of cut segments prepared fromt fruit. Fruit tastewas evaluated by a trained panel con-members,vemalesandve females, aged2562.Eachessed the various attributes of three samples, accordinguctured 100-mm scale, with anchor points very weakrong for each attribute, and sensory datawere recordeds (mm) from the origin. The samples were identied byandomly assigned three-digit codes. In addition, pan-requested to rate overall fruit avor preference on a: 1 =very bad, 2 =bad, 3 = fair, 4 = good, and5=excellent.y analysis scores of oranges and grapefruit presentedeans of three independent experiments, and those ofare means of six independent experiments.

    is of aroma volatiles

    olatiles were extracted from homogenized segmentso Tietel et al. (2010a). Fruit were hand-peeled, weighed,d for 30 s with an equal amount of 30% NaCl (w/v),nzymatic degradation. Aliquots (2mL) were placed invials, and 5L of 1-pentanol (SigmaAldrich, St. Louis,d 1:1000 in water, were added as an internal standard.ere stored at 20 C pending analysis.olatiles were determined by three replicate measure-prepared from three different fruit, i.e., a total of ninee point. They were identied by gas chromatographyd with mass spectrometry (MS). Prior to analysis, sam-llowed to equilibrate for 5min at 40 C, afterwhich theyated at the same temperature for an additional 25min.ere extracted by solid-phase microextraction (SPME).bers, 1 cm in length, coated with a 50/30m layer ofene/carboxen/polydimethylsiloxane (DVB/CAR/PDMS)ellefonte, PA) were used to trap volatile compounds ineadspaces. After incubation, the bers were desorbed250 C in the splitless inlet of a Model 7890A GC (Agi-to, CA) equippedwith anHP-5 column (30m0.25mmlm thickness) (J&W Scientic, Folsom, CA). The oven

    mmed to run at 50 C for 1min, to ramp up to 160 C atthen to ramp up to 260 C at 20 Cmin1, and to remainperature for 4min. The helium carrier-gas ow was setin1. The efuent was transferred to a Model 5975CMSgilent, Palo Alto, CA) that was set to scan from mass 402 scans/s, in the positive-ionmode, andmass spectra inimpact (EI) mode were generated at 70eV. Chromato-ks were identied by comparing the mass spectrum ofnent with the US National Institute of Standards and(NIST) library of mass spectra, 2006 version. Identi-

    aroma volatiles was further conrmed by calculatingretention indices (RIs) by comparison with a series of

  • 52 L. Mayuoni et al. / Postharvest Biology and Technology 62 (2011) 5058

    Fig. 1. Visual

    n-alkanes (Cdatabases orus Flavor Dof interestinternal staThe identitmethylbuta-terpinene4-ol werestandards.

    2.6. Determ

    Phenolssamples wappearance of Navel oranges, Star Ruby grapefruit and Satsuma mandarins at harvest

    5C20) and comparing their values with the publishedf Adams (2001) and the University of Florida Cit-atabase (http://www.crec.ifas.u.edu/rouseff/). Peakswere semi-quantied by comparison with added

    ndards, and are expressed as 1-pentanol equivalents.ies of 11 compounds, including -pinene, ethyl 2-noate, hexanal, -myrcene, -terpinene, limonene,, octyl acetate (E)-2-nonenal, linalool, and 1-terpinen-further conrmed by running authentic chemical

    ination of total phenols and avonoids

    and avonoids were extracted by stirring 1mL juiceith 9mL of 80% methanol for 30min at room tem-

    perature, fTotal pheno(Singleton0.2mLof juand 7mL of90minat romeasuredaphenolic co

    Total aBriey, theextracts, 0.3mixtures w1N NaOH wwas adjustecontents wand after 24, 48 and 72h of exposure to ethylene at 4L L1 at 20 C.

    ollowed by centrifugation at 10,000 g for 10min.lics were determined by the FolinCiocalteu method

    et al., 1999). Briey, the reaction mixtures comprisedicemethanol extracts, 0.2mLof FolinCiocalteu reagent,7% Na2CO3. The reaction mixtures were incubated foromtemperature, afterwhich absorbance at 750nmwasgainst apreparedblankwitha spectrophotometer. Totalntents were expressed as gallic acid equivalent (GAE).vonoidsweredeterminedaccording to Shin et al. (2007).reaction mixtures comprised 1.0mL of juice methanolmL of 5% NaNO2 and 0.3mL of 10% AlCl3. The reaction

    ere incubated for 10min at room temperature, 2mL ofere added to stop the reaction, and the total volumed to 10mL by adding double-distilled water. Flavonoidere measured by comparing the absorbance at 510nm

  • L. Mayuoni et al. / Postharvest Biology and Technology 62 (2011) 5058 53

    Fig. 2. Evaluatto air or to eth

    with that ofequivalent

    2.7. Antioxi

    Total anradical catimixture coazinobis-(3solved in areactionmiAfterwardswith that ofthe degreeabsorbanceEquivalent(mM)= (Absresults werity (TEAC), cV= sample v

    2.8. Statisti

    One-waywise compstatistical sMicrosoft Oion of respiration and ethylene production rates of Navel oranges, Star Ruby grapefruitylene at 4L L1 at 20 C. Data are means SE of six replications.

    a prepared blank, and results are expressed as catechin(CE).

    dant activity

    tioxidant activity was determined by using the ABTS*+

    on assay (Miller and Rice-Evans, 1997). The reactionmprised 1mL of 75M K2O8S2 and 150M 2,2--ethylbenzothiazoline-6-sulfonic acid) (ABTS*+) dis-cetate buffer, pH=4.3, and a 10L juice sample. Thextures were incubated for 15min at room temperature., total antioxidant activity of juice samples, as compareda 1mM trolox solution, was measured by determiningof disappearance of the blue color by comparing theat 734nm against that of a prepared blank. The Trolox(TE) was calculated according to the formula: TE valuesampleAbs blank)/(Abs standardAbs blank). The

    e expressed as Trolox Equivalent Antioxidant Capac-alculated as: TEAC (MTE/g) = (TEV)/(1000M) inwhicholume and M= sample weight.

    cal analysis

    analysis of variance (ANOVA) and Tukeys HSD pair-arison tests were applied by means of the SigmaStatoftware (Jandel Scientic Software, San Rafael, CA), andfce Excel programs.

    3. Results

    3.1. Effectsproduction

    We examon ripeningStar Rubyin all the t72h graduaorange/redaffected pe

    To evalurelated proeffects ontested citruethylene terates then tIn all cultivwere moretrol fruit hethylene alall fruit, froafter 2448ulated respwhich areindicating iand Satsuma mandarins at harvest and after 24 and 48h of exposure

    of ethylene degreening on respiration and ethylene

    ined the stimulating effects of ethylene degreeningprocesses and on internal quality of Navel oranges,

    grapefruit and Satsuma mandarins. It can be seen thatested citrus species, exposure to ethylene for up tolly accelerated the change of peel color from green to/yellow (Fig. 1), whereas exposure to air alone barelyel color change (data not shown).ate the effects of exogenous ethylene on ripening-cesses and metabolic activity, we rst examined itsrespiration and ethylene-production rates. In all thes fruit, oranges, grapefruit and mandarins, exposure tomporarily enhanced respiration rates after 24h, but theended to revert to their initial time-zero levels (Fig. 2).ars, respiration rates after 24h of exposure to ethyleneor less double those observed at time zero or in con-eld in air (Fig. 2). In addition, exposure to exogenousso enhanced endogenous ethylene production rates inm 0.2gkg1 h1 at time zero to 0.81.2gkg1 h1h (Fig. 2). Thus, ethylene degreening of citrus fruit stim-iration and increased ethylene production rates, both offundamental parameters of climacteric fruit ripening,ncreased overall metabolic activity in the fruit.

  • 54 L. Mayuoni et al. / Postharvest Biology and Technology 62 (2011) 5058

    Fig. 3. Evaluatto ethylene at

    3.2. Effects

    The tastcontents, afound thatTSS or acididetailed athat ethyleand grapefr(Fig. 4). Theto ethylenetypical mandecrease infruit for 5 dethylene deof the teste

    3.3. Effectscomposition

    Overall,Navel oran48 volatilesS1S3). Weat 20 C hasitions in coranges, exion of TSS and acidity levels in juice of Navel oranges, Star Ruby grapefruit and Satsum4L L1 at 20 C. Data are means SE of ve replications.

    of ethylene degreening on taste and avor

    e of citrus fruit is principally governed by TSS and acidnd the ratio between them. In the present study, weethylene degreening did not have any effect on juicety levels in any of the tested fruit (Fig. 3). Furthermore,vor evaluations with the aid of a trained panel revealedne degreening had no effect on the avor of orangesuit, but marginally impaired the avor of mandarinsobserved loss of mandarin avor following exposurewas attributed to a slight decrease in the perception ofdarin avor (Fig. 4). At least part of the observed slightavor acceptability could be attributed to storage of theays at 20 C, even without ethylene (Fig. 4). In any case,greening did not enhance off-avor sensations in anyd fruit (Fig. 4).

    of ethylene degreening on aroma volatile contents and

    our SPME/GCMS analysis detected 54 volatiles inge juice, 62 volatiles in Star Ruby grapefruit juice, andin Satsuma mandarin juice (Supplementary Tablesfound that exposure to ethylene at 4L L1 for 72h

    d only minor effects on volatile contents and compo-itrus juices (Table 1). For example, in juice of Navelposure to ethylene decreased the contents of two alde-

    hyde volatiof three carvone]; in Sthe contentand (E)-2-oincreased tterpinene-4or decreaselowed degrfruit, therestorage ofeffect of etlevels of citand controthree terpeethylene-trnot enhancethyl acetat

    3.4. Effects

    In orderfruit nutritiavonoids cAt time zerStar Ruby21mg/100a mandarins, at harvest and after 24, 48, or 72h of exposure to air or

    les [(Z)-3-hexenal and citronellal], and increased thosevone-derived volatiles [(E)-carveol, (Z)-carveol and car-tar Ruby grapefruit, exposure to ethylene increaseds of four aldehydes [pentanal, (E)-2-hexenal, 2-heptenalctenal]; and in Satsuma mandarins ethylene exposurehe contents of three terpene-derived alcohols [linalool,-ol and -terpineol] (Table 1). In some cases, increasess in aroma volatile contents similar to those that fol-eeningwere observed also in juices of air-stored controlfore, the changes in their levels could be attributed tothe fruit at 20 C for 3 days rather than to the directhylene (Table 1). For example, in Navel oranges, theronellal decreased similarly in both ethylene-exposedl fruit, and in Satsuma mandarins, the levels of allne-derived alcohols were similar in both control andeated fruit (Table 1). Lastly, exposure to ethylene dide accumulation of off avor volatiles, such as ethanol ore, as might have been expected (Table 1).

    of ethylene degreening on nutritional quality

    to evaluate the effects of ethylene degreening ononal quality, we examined vitamin C, total phenol andontents, and total antioxidant activities of citrus juices.o, the levels of vitamin C in juice of Navel oranges,grapefruit, and Satsuma mandarins were 48, 32, andmL, respectively. In Navel oranges, we detected a slight

  • L. Mayuoni et al. / Postharvest Biology and Technology 62 (2011) 5058 55

    Fig. 4. Evaluation of the sensory quality of Navel oranges, Star Ruby grapefruit, and Satsuma mandarins at harvest and after 72h of exposure to air or to ethylene at4L L1 at 20 C. Figures on the left indicate overall taste score evaluations, whereas gures on the right represent avor prole analyses. Fruit avor was evaluated by atrained taste panel. Data are means SE of 10 replications.

    Table 1Aroma volatiles whose contents increased or decreased following ethylene degreening in homogenized segments of Navel oranges, Star Ruby grapefruit and Satsumamandarins.

    Concentration (g L1)

    Compound RI At harvest Air (72h) Ethylene (72h)

    Navel orange(Z)-3-Hexenal 800 697 354 Citronellal 1152 471 (E)-Carveol 1201 94 108 527(Z)-Carveol 1219 134 1154 2316Carvone 1244 232 626 1461

    Star Ruby grapefruitPentanal 700 174(E)-2-Hexenal 851 108 126 4862-Heptenal 955 135(E)-2-Octenal 1058 115

    Satsuma mandarinLinalool 1099 375 890 1075Terpinene-4-ol 1177 98 234 217-Terpineol 1190 143 370 388

    Data represent aroma volatiles whose contents increased or decreased signicantly (P0.05) and by factors of at least 2, following exposure to ethylene at 4L L1 for 72hat 20 C. The presented data are 1-pentanol equivalents, and are means of three measurements, each of juice collected from three different fruit.

  • 56 L. Mayuoni et al. / Postharvest Biology and Technology 62 (2011) 5058

    Fig. 5. Evaluaexposure to ai

    decrease inzero to aboudecrease wtherefore, wto storage osumamandC levels eith

    With regtents in citthe contentfruit juicesin Satsumadegreenedavonoids cper 100g FWdegreened fin total av100g FW. Instable, at abthe degreen

    Finally,affect on tothat the avorange, Staapproximataffected bytion of total phenol and avonoid levels in juice of Navel oranges, Star Ruby grapefrur or to ethylene at 4L L1 at 20 C. Data are means S.E. of ve replications.

    vitamin C levels in juice, from 48mg/100mL at timet 4042mg/100mL after 3 days at 20 C. However, thisas observed in both control and degreened fruit and,as not attributed to exposure to ethylene but ratherf the fruit. In juices of Star Ruby grapefruit and Sat-arins, we did not detect any notable changes in vitaminer during the control or the degreening treatments.ard to evaluation of total phenol and avonoids con-rus juices, we did not detect any notable changes ins of total phenolic compounds in orange and grape-, but did observe a slight decrease in total phenolics mandarin juices which occurred in both control andfruit. In Navel oranges, a slight decrease in totalontent, from4.2mg per 100g FWat time zero to 2.5mgafter 72h at 20 C was observed in both control and

    ruit. In grapefruit juice, we observed some uctuationsonoids levels, which ranged from 5.5 to 9.5mg perSatsuma mandarin juice, total avonoids levels wereout 8.08.5mg per 100g FW, and were not affected bying treatment.we examined whether ethylene degreening had anytal antioxidant activities in citrus juices. It was founderage levels of total antioxidant activities of Navelr Ruby grapefruit, and Satsuma mandarin juices wereely 5, 4, and 2MTEg1, respectively, and were notexposure to ethylene.

    4. Discussi

    Citrus frlene, both epeel color c1993; Rodrwhether ethcesses in th

    In lightand improof some prharmed oveuse three mto evaluateinternal ripon determi

    The predegreening(Fig. 1) andduction ratinternal fruity levels incompositioS1S3), vita(Fig. 5), anethylene isit, and Satsuma mandarins, at harvest and after 24, 48 and 72h of

    on

    uit are non-climacteric, but it is well known that ethy-ndogenous and exogenous, is involved in regulation ofhange (Purvis and Barmore, 1981; Goldschmidt et al.,igo and Zacarias, 2007). However, it is not yet knownylene is involved in regulation of internal ripening pro-e citrus esh.of the increased importance attached to maintenancevement of internal fruit quality, and of the ndingsevious studies that ethylene degreening might haverall fruit quality, the goal of the present study was toain citrus species, orange, grapefruit and mandarin,systematically whether ethylene degreening affectedening processes in citrus fruit, with especial emphasisnation of fruit avor and nutritional quality aspects.sent results clearly show that although ethylenefor up to 3 days at 20 C accelerated peel color changetemporarily increased respiration and ethylene pro-

    es (Fig. 2), it did not have any major effects on variousit-quality parameters, including TSS contents and acid-juice (Fig. 3), avor perception (Fig. 4), contents and

    n of aroma volatiles (Table 1, Supplementary Tablesmin C content, total phenols and avonoids contentsd overall antioxidant activity. Thus we conclude thatprobably not involved in regulation of internal ripening

  • L. Mayuoni et al. / Postharvest Biology and Technology 62 (2011) 5058 57

    processes in citrus esh, and therefore, does not affect or impairinternal fruit quality attributes, including perceived avor andnutritional quality. Our current results are somewhat in contra-diction with our previous ndings demonstrating that exposureto ethylenein mandarithe identisuewere inof general mstress tolerainternal frugenes involto cause ma

    Regardinfruit avorthat ethyleonly excepacceptabilitnomenon cfruit at 20

    more perishrapid declin2011). Thershelf-life teethylene deimpair fruitat higher teity levels (Tthe detectioLadaniya antures of 27(2002) alsoin oils thatmore, in cliethylene enalcohol aceet al., 2007)any accumusuggestingerned by etnot controlnon-climac

    With regquality, ouraffect the ovfound thatgene exprepeel (Cajuswe did not dble explanaaccount forpresent inandphenylplation of thcompoundsof other stuavonoid c2002).

    Finally, oof a recentcolor changand a late-rception; thesynthesis antheless, thesuch as juic

    in our present case, it was concluded that ethylene affected peelcolor-break but not internal fruit quality parameters.

    Acknowledgments

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    midt,lene?midt,ethyth Re, W.,Stat. BK., Kuwation opped-.A., 2186, M.Sus sine, J.M.,ning. Poto, Hosthardo anChem

    i, L., Sheenin582on, Woff-a.J., Riced bya, K.,

    pound71, 29, S., CrScieninuenced the expression patterns of 661 transcriptsn esh (Mayuoni et al., 2011). Nevertheless, most ofed degreening-regulated genes in mandarin esh tis-volved rather in governingmetabolic arrest (slowdownetabolic activity) and activation of biotic and abioticnce; both factors are not directly involved in regulatingit quality parameters. Moreover, the slight activation ofved in metabolic processes was probably not sufcientrked changes in fruit avor or nutritional quality.g the evaluation of possible effects of ethylene onperception, our results support the common dogmane does not affect citrus fruit avor perception. Thetion was observed with mandarin fruit, where avory slightly decreased following degreening, but this phe-ould be attributed, at least partly, to storage of theC for 5 days (Fig. 4). It is known that mandarins areable than other citrus fruit, and especially suffer frome in sensory acceptability after harvest (Tietel et al.,efore, it is recommended not to keep mandarins atmperatures for long periods. Although we claim thatgreening at moderate temperatures (20 C) did notavor, it should be noted that degreening citrus fruitmperatures of 30 C led to a decrease in juice acid-ietel et al., 2010b). This observation is consistent withn of decreased acidity levels in Mosambi oranges byd Singh (2001) following degreening at high tempera-29 C. Similar to our present ndings, Nishikawa et al.did not observe any changes in aroma volatile proleswere cold-pressed from degreened oranges. Further-macteric fruit, such as apple and banana, exposure tohances accumulation of ester volatiles via activation oftyl transferases (AATs) (Golding et al., 1999; Schaffer. Nevertheless, in the present study we did not detectlation of ester volatiles after the degreening treatmentthat aroma volatile production in citrus fruit is not gov-hylene. A similar conclusion that volatile emission wasled by ethylene was recently reported in the case ofteric cut roses (Borda et al., 2011).ard to possible effects of ethylene on fruit nutritionalresults clearly show that ethylene degreening did noterall nutritional quality of citrus fruit. Previous studiesethylene induced phenylalanine ammonia lyase (PAL)ssion and phenylpropanoid metabolism in mandarinte and Lafuente, 2007). However, in the present studyetect any increase in total phenolic compounds. Possi-tions for these differences are that phenylpropanoidsjust a minor part of the total phenolic compounds

    the juice cells, or, alternatively, that activation of PALropanoidmetabolismmight result inmassive accumu-

    e nal biosynthetic product, lignin, but not of phenolicper se. Otherwise, our results are consistentwith thosedies in which no signicant inuences of ethylene onontent in citrus esh were observed (Nishikawa et al.,

    urpresentndingsalsoare in full agreementwith thosestudy by Distefano et al. (2009), who evaluated peele and internal characteristics of a normal Clementineipening Clementine mutant defective in ethylene per-y found that the Tardivomutant, defective in ethylened perception, showed delayed color-break but, never-mutationdidnot affect internal ripening characteristicse acidity and TSS levels (Distefano et al., 2009). Thus, as

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    NormanHortuscript is contributionno. 606/11 from theAgriculturalrganization, the Volcani Center, Bet Dagan, Israel. Thisas supported by Research Grant No. TB-8056-08 fromIsrael Exchange, and BARD, the United States Israelgricultural Research and Development Fund.

    . Supplementary data

    entary data associatedwith this article can be found, inersion, at doi:10.1016/j.postharvbio.2011.04.005.

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    Does ethylene degreening affect internal quality of citrus fruit?1 Introduction2 Materials and methods2.1 Plant material2.2 Ethylene degreening2.3 Juice soluble solids, titratable acidity, and ascorbic acid contents2.4 Sensory evaluations2.5 Analysis of aroma volatiles2.6 Determination of total phenols and flavonoids2.7 Antioxidant activity2.8 Statistical analysis

    3 Results3.1 Effects of ethylene degreening on respiration and ethylene production3.2 Effects of ethylene degreening on taste and flavor3.3 Effects of ethylene degreening on aroma volatile contents and composition3.4 Effects of ethylene degreening on nutritional quality

    4 DiscussionAcknowledgmentsAppendix A Supplementary dataReferences

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