Acta Hortic. 1120. ISHS 2016. DOI 10.17660/ActaHortic.2016.1120.47 XXIX IHC – Proc. Int. Symposia on Postharvest Knowledge for the Future and Consumer and Sensory Driven Improvements to Fruits and Nuts Eds.: J.B. Golding et al. 311 Methods to evidence mechanical injuries on ‘Packham’s Triumph’ pears J. Pasini 1 , R.J. Bender 1 and L.R. Antoniolli 2 1 Laboratório Pós‐colheita, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brazil; 2 Embrapa Uva e Vinho, Bento Gonçalves, RS, Brazil. Abstract Mechanical injuries are responsible for most of the postharvest fresh produce losses. Changes in plant tissues resulting from mechanical damages might remain unnoticed for some time. Some slight lesions are not detectable by hasty visual inspections but can contribute to speed up postharvest deterioration. Therefore, the objective of the present study was to evaluate the efficacy of different methods to evidence mechanical injuries on ‘Packham’s Triumph’ pears. Pears of different sizes were packed into plastic boxes and placed in an orbital shaker to inflict mechanical damages by friction at up to 210 revolutions min -1 (rpm) for 20 min. Mechanical injuries were determined after a) bagging the pears in low density polyethylene for 24 h, b) immersion in a 0.1% (w/v) 2,3,5-triphenyl tetrazolium chloride solution for 20 h or c) exposure for 2 h to 3 mL L -1 (v/v) sulfur dioxide (SO 2 ). After these periods the pears were visually evaluated and ranked for occurrence of mechanical damages based on a scale ranging from zero (no injury) to five (severe damages). The highest rotations resulted in the most severe lesions. Presence of cuts was considered the most severe level of damage. 2,3,5-triphenyl tetrazolium evidenced lesions inflicted on the pears at 70 rpm and even on the control fruit. At 140 and 210 rpm all detection methods did signal the inflicted lesions. 2,3,5-triphenyl tetrazolium solutions are capable to stain more indelible damages which may occur at harvest and postharvest procedures of ‘Packham’s Triumph’ pears. Keywords: Pyrus communis L., 2,3,5‐triphenyl‐tetrazolium chloride, sulfur dioxide INTRODUCTION Mechanical injuries are accountable for high percentages of fruit postharvest losses. Injuries might be caused by impacts, friction or compression forces and occur at any stage of the postharvest handling chain (Chitarra and Chitarra, 2005). Pears (Pyrus communis L.) are very susceptible to mechanical injuries, markedly to those caused by friction. The frictional damages typically come about during transport because of fruit rubbing against package walls. The friction damages result in epidermal discoloration, which might spread out to subepidermal cells. Browning is a consequence of phenolics oxidation by way of polyphenol oxidase activity (Berardinelli et al., 2005). Vegetable tissue changes might be induced by either noticeable or not visible damages. Some lesions, with a diameter smaller than 100 µm are not detected visually, nonetheless they might contribute to speeding up after harvest deterioration processes (Amiri and Bompeix, 2005). There are techniques to attest tissue injuries such as laser scanning confocal microscopy (Veraverbeke et al., 2001), scanning electronic microscopy (Montero et al., 2009) and electrical impedance spectroscopy (Jackson and Harker, 2000). Albeit these methods are exceptionally unbeaten to evidence mechanical injuries, their application is restricted because of high cost equipment. From that perspective Amiri and Bompeix (2005) tested gaseous sulfur dioxide on apples and pears in the likelihood to hasten tissue browning to appraise the extent of injures. The authors concluded that sulfur dioxide was able to evidence lesions of 0.1 mm. Yuri et al. (2005) related the use polyethylene bags as a method to speed up oxidative processes in the epidermis and mesocarp of apples ensuing tissue browning in a shorter period of time.
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Acta Hortic. 1120. ISHS 2016. DOI 10.17660/ActaHortic.2016.1120.47 XXIX IHC – Proc. Int. Symposia on Postharvest Knowledge for the Future and Consumer and Sensory Driven Improvements to Fruits and Nuts Eds.: J.B. Golding et al.
311
Methods to evidence mechanical injuries on ‘Packham’s Triumph’ pears
Abstract Mechanical injuries are responsible for most of the postharvest fresh produce
losses. Changes in plant tissues resulting from mechanical damages might remain unnoticed for some time. Some slight lesions are not detectable by hasty visual inspections but can contribute to speed up postharvest deterioration. Therefore, the objective of the present study was to evaluate the efficacy of different methods to evidence mechanical injuries on ‘Packham’s Triumph’ pears. Pears of different sizes were packed into plastic boxes and placed in an orbital shaker to inflict mechanical damages by friction at up to 210 revolutions min-1 (rpm) for 20 min. Mechanical injuries were determined after a) bagging the pears in low density polyethylene for 24 h, b) immersion in a 0.1% (w/v) 2,3,5-triphenyl tetrazolium chloride solution for 20 h or c) exposure for 2 h to 3 mL L-1 (v/v) sulfur dioxide (SO2). After these periods the pears were visually evaluated and ranked for occurrence of mechanical damages based on a scale ranging from zero (no injury) to five (severe damages). The highest rotations resulted in the most severe lesions. Presence of cuts was considered the most severe level of damage. 2,3,5-triphenyl tetrazolium evidenced lesions inflicted on the pears at 70 rpm and even on the control fruit. At 140 and 210 rpm all detection methods did signal the inflicted lesions. 2,3,5-triphenyl tetrazolium solutions are capable to stain more indelible damages which may occur at harvest and postharvest procedures of ‘Packham’s Triumph’ pears.
INTRODUCTION Mechanical injuries are accountable forhighpercentagesof fruitpostharvest losses.
Injuriesmightbecausedbyimpacts,frictionorcompressionforcesandoccuratanystageofthepostharvesthandlingchain(ChitarraandChitarra,2005).Pears(Pyrus communisL.)areverysusceptibletomechanicalinjuries,markedlytothosecausedbyfriction.Thefrictionaldamages typically come about during transport because of fruit rubbing against packagewalls. The friction damages result in epidermal discoloration, whichmight spread out tosubepidermalcells.Browningisaconsequenceofphenolicsoxidationbywayofpolyphenoloxidaseactivity(Berardinellietal.,2005).
Vegetabletissuechangesmightbeinducedbyeithernoticeableornotvisibledamages.Some lesions,withadiameter smaller than100µmarenotdetectedvisually,nonethelessthey might contribute to speeding up after harvest deterioration processes (Amiri andBompeix, 2005). There are techniques to attest tissue injuries such as laser scanningconfocalmicroscopy(Veraverbekeetal.,2001),scanningelectronicmicroscopy(Monteroetal.,2009)andelectricalimpedancespectroscopy(JacksonandHarker,2000).
Albeitthesemethodsareexceptionallyunbeatentoevidencemechanicalinjuries,theirapplication is restrictedbecauseofhighcost equipment. From thatperspectiveAmiri andBompeix (2005) tested gaseous sulfur dioxide on apples and pears in the likelihood tohastentissuebrowningtoappraisetheextentofinjures.Theauthorsconcludedthatsulfurdioxide was able to evidence lesions of 0.1 mm. Yuri et al. (2005) related the usepolyethylene bags as a method to speed up oxidative processes in the epidermis andmesocarpofapplesensuingtissuebrowninginashorterperiodoftime.
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Mechanicalinjuriesonseedsofmaize(Oliveiraetal.,1998),soybeans(Marcondesetal.,2005;Lopesetal.,2001)andzucchini(Barrosetal.,2005)mightbeevidencedbywayofan immersion into a 2,3,5‐triphenyl‐tetrazolium chloride (TTC) solution. The TTC testperfected byMoore in 1972 is based on life tissuemetabolism reflecting dehydrogenasesactivity involved in respiratory processes. Predominantly, in mitochondrial oxidationshydrogen ions are released rendering the opportunity them to react with TTC yieldingtriphenylformazan(tetrazoliumredformazan),areddishand insolublemetabolite(FrançaNetoetal.,1998)assistinginthepossibilitytotellapartlivingtissues,coloredinred,fromdeadtissues,whichmaintaintheoriginalcolor.
In the present work, the objective was to evaluate the effectiveness of differenttechniquestoevidencemechanicalinjurieson‘Packham’sTriumph’pearsinordertorevealdamageincidenceatharvestandpostharvestprocedures.
MATERIAL AND METHODS ‘Packham’s Triumph’ pearswere harvested from a commercial orchard close to the
cityofSaoFranciscodePaula,RioGrandedoSul,thesouthern‐moststateinBrazil.Toavoidinjuriesatharvestand transport to the lab theharvested fruitwereplaced inpaper traysandwrappedwithplasticfilmandthenplacedboxes.Theboxeswereaswellenfolded.
Pearsfromallcaliberswereclassifiedanddistributedinplasticboxes(55×18×36cm).With an orbital shaker (Fanem, 255B) the following treatmentswere applied for 20min:control(0rotationsmin‐1),70,140or210rpm.Immediatelyafterinflictingthedamagesthepearswereeitherpackedinlowdensitypolyethylenebagsof8micrathickness,immersedfor20hat30±2°Cinabsenceof lightina0.1%(w/v)2,3,5‐triphenyl‐tetrazoliumchloridesolutionorexposedfor2hinahermeticchambertosulfurdioxide(SO2)ataconcentrationof 3mL L‐1 (v/v). The individually bagged fruitweremaintained for 24 h at 30±2°C. Thepears for the TTC treatment had been previously washed with a neutral detergent andafterwardsrinsedthreetimesindistilledwater.
Identification of sulfur dioxide damages was performed as described in Amiri andBompeix(2005)withadaptations.Thepearswereplacedsidebysideinanacrylicboxof40L internal volume.The internal airwas removedwithavacuumpump, andsulfurdioxidewas injectedwitha20mLsyringe throughasiliconeseptum. Inside,at thebottomof thebox,asmallventilatorhomogenizedtheinternalairvolume.After2htheboxwasopenedandtreatedfruitaeratedfor24h.
Themagnitudeof thedamageswasevaluatedvisuallyaftertreatmentapplicationbymeansofaratingscaleadaptedfromSlaughteretal. (1993):rankingzero(nodamagesatall)up toranking five (veryseveredamages).Rankingone=veryslightdamages; rankingtwo = slight damages; ranking three = moderate damages and ranking four = severedamages.
RESULTS AND DISCUSSION Using the pears of the experiment, a numerical scale of extent of damages for each
testedmethodwas developed (Figure 1). The ranking zero indicates absence of damageswhilerankingfiveindicatesthemaximumrateofdamages.
As higher rotations were applied, the lesions became more severe and the gradesassigned according to the scalewere higher (Figure 2). In the control treatment, the TTCtreatment signaled damages in 100% of the fruit even with the protecting measuresundertakenatharvestandforthetransportofthefruit.Thusfar,however,thelesionswererankedasveryslightuptomoderatedamages.
Figure1. Numerical scale of extent of damages on ‘Packham’s Triumph’ pears fortechniques to evidence mechanical injuries: low density 8 micra thickpolyethylenebags (A); 0.1% (w/v)2,3,5‐triphenyl‐tetrazoliumchloride solution(B)andfumigationwithsulfurdioxide(SO2)at3mLL‐1(v/v)(C).Rankingzero(no damages at all); Ranking one = very slight damage; ranking two = slightdamage; ranking three=moderatedamage; ranking four=severedamagesandrankingfive=veryseveredamage.
Figure2. Frequencydistributionofrankingsattributedto‘Packham’sTriumph’pearsaftersubmissiontodifferentvibration intensities:control(0rotationsmin‐1),70,140or 210 rpm for 20min techniques to evidencemechanical injuries via bagginginto lowdensitypolyethylenebagsor immersion in0.1%(w/v)2,3,5‐triphenyl‐tetrazoliumchloridesolutionorfumigationwithsulfurdioxide(SO2)at3mLL‐1(v/v);Rankingzero(nodamageatall);Rankingone=veryslightdamage;rankingtwo = slight damage; ranking three =moderate damage; ranking four = severedamageandrankingfive=veryseveredamage.
part of the pearswere ranked aswithmoderate damages and yet 13% of the fruit wereranked as with slight damages. The TTC and sulfur dioxide treatments categorized themajorityofthefruitaswithsevereandveryseveredamages,respectively.
The pears consigned to polyethylene bags presented immediately after treatmentapplicationepidermalbrowning,whichisanevidentsignalofinjureincidence.Afterlesionoccurrence, the affected tissues darken rapidly because tissue ruptures and subsequentoxidation. According to Yuri et al. (2005) injure symptoms appearance is hastened inpolyethylenebagsinresponsetotheincreasesintemperatureinsidethebags.
Browning was more evident at 140 rpm and beyond. At the highest rotation evenfracturesintheepidermiscouldbevisualized.Thepresenceoffractureswasconsideredthehighestlevelofdamages.Browning,however,didnotspreadouttosubepidermallayersandmesocarptissuesremainedwithitscolorunaltered.
Sommer(1957)indicatedthatfrictiondamagesaremorerestrictedtosuperficialcelllayers and mesocarp tissue, more often than not, remain undamaged. Berardinelli et al.(2005) transportedpears fora520kmjourneyanddiddetectdamages to thepulpof thefruit.Barchietal.(2002),aswell,concludedinthesamewaysubsequentlytoshippingpearsfor1200km.Agar andMitcham (2000), in contrast, however, reckoned that small lesionsoccur after frictions. The authors, though, correlate the lesions to the intensity of thedamage.
Thedamagedareassubmittedtotetrazoliumimpartalightbrowncolorwithaborderofintensered.FrançaNetoetal.(1998)indicatethatmalatedehydrogenasereducesTTCinlivingtissues.AsTTCdiffusesintodamagedtissues,thecompoundspreadsoutintotissueswhereitsreductionresultsintheformationof1,3,5‐trifenilformazan.Formazansynthesisisan indication of intense respiratory activity at the damaged areas. Several authors havedemonstratedthataftermechanicalinjuriesanincrementinrespirationratesisuniversal,asdetermined in pears by Agar and Mitcham (2000), in apples by Montero (2010) andavocadosbySanchesetal.(2008).
Fumigationwithsulfurdioxidecausesanecrosisat thedamagedsite.Theborderofthewound presents a darker color. Oxidation and polymerization of phenolic compoundsare presumed to cause the darkening (Underhill and Critchley, 1992). Stratford and Rose(1986) demonstrated that cytoplasm sulfur dioxide build up resulted in pH reductionssimultaneously to higher resistance of epidermal tissues to carbon dioxide diffusion.According to the same authors, such modifications associated to respiratory activity ofinternal tissuescouldwindup inelevatedoxygendepletions inthesetissues.Asoxygenisnecessarytopolyphenoloxidaseactivity,hypoxiacouldpreventbrowningofinternaltissuesimpartingamorecolorlessnecrosisofthedamagedtissues(Banks,1985).
Whereas the external appearance is one of the main aspects taken into account atpurchaseitisplausibletoinferthatlowdensitypolyethylenebagsevidenceinjuries,whichineffectbecomevisiblethroughoutmarketingandwillbeeasilynoticedbyconsumers.
the fruit into 2,3,5‐triphenyl‐tetrazolium solution or fumigating with sulfur dioxide aremethodstobeusedtosignalmechanicalinjuriesonpearsatharvestandalongafterharvesthandling procedures. Immersion of ‘Packham’s Triumph’ pears into a 2,3,5‐triphenyl‐tetrazoliumsolutionhasthecapabilitytoevidenceveryslightpeeldamagesinflictedalongharvestingandpostharvesthandlingprocedures,which,otherwise,wouldhardlynoticed.
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