Effects of Hot Water Treatment on Reducing Chilling Injury ofPomegranate (Punica granatwz) Fruit during Storage

S.H. Mirdehghan and M. RahemrDept. of Horticulture, College ofAgricultureShiraz UniversrtYShinzTran

Ke1'rvords: browning, electrol)te leakage, potassium ion leakage, '\4alas Yazdi', 'Malas

Saveh'

AbstractIn an initial experiment comparing hot water and chemicill effects on chilling

ho1monal heatments.

:r9c 5'Int Postharvesr Syip.los l. Mencarelli and P. ToruftiActa l l .n Kar rerre ) l r^<

iDiur\, 'Mafa\ Yazdi" and 'r4aias'Sare-h' pomegranates IPunlca granatuml weriaibpea in hot water at 50 and 75oC, imazalil (1 and 3 ml,rl,) an{ benzyladenine (80ano 100 mgn-) for 2 and 5 min. Distilled wa.ter ̂ t 25"C was useal as a controltreatment. lreated fruit were stored at 1.5oC and 85+3% RII for 4.5 months.Atthough $'ater at 75oC resulted in heat injury of fruit, hot watei at 50oC compareilwith the other treatments sigoificantly reduced chilling inijury. In a secondexperiment, 'Malas Yazdi' pomegranates were dipped in hot wfiter at 25 (control),35,45, 55 and 65oC for 2 and 5 min. Treated fruit were stored for 3 months underthe same conditions as used in the first experiment. The iesults showed thatjncreasing tbe $ater temperalure to 45oC significantly reduced chill ing injurl.electrolvri and K' leakage bul had oo significant effect oo tolal soluble souds- totalacidity, ascorbic acid and pH of fruit after remoYal from storagel

INTRODUCTIONThe ponegranate (Punica granaunt) is a subtroplcal fixit tee that is native to the

Middie Easi (esp6cially lian). This species belongs to -the

Punicaciae and is one of theoldest knowr'edibie A"itr. ihe t"tit ii round with a prominent attached callx and a hardleathery skin (Badizadegan and Khabbaztan, 1977).-The

storage temperature recommended for pomegranates vhries from 0 to 10'Cwith a storage hfJ rangiig ftom 2 weeks to 7 rnonthi dependhg ol the cultivar. However,Elyatem andKadar (1i84) showed that storage ofpomegranatei at 5"C or lower results i]lchiiLi"g i"j"rl, (C!, marilfest as brown discoloration

-of the skr:n, suface pittin-g ard

sL,scep"tiUiiityio'delay organisnls. Inremal symptoms include a palel aril color and browndiscororarion oI dre u hite segments separating the arils.

. Severul posthawest ireatments- have -beel

designed ro impiove 1ow tempemturestomse of chillirs-sensitive ffuit. These tueatnents include chemiQal ffeatments such asthiabEndazole (iiazalil), homone treabnents such as benzyladeirine (BA), and heatteatments, e.g. hot water ard intermittent warming.

Heat ieatments have been shown to redu& sensivi6' to lolrf. temperature damagein persimmons (Bumeister et al., 1997), tomatoes (Lurie and KJeinl 1991) and kumquats(Sahiraa et al." L995). BA and imazalil have also Droved to be effectrive in reducing CI ingrape&uit (Sahiffmann-Nadel er al., 19'75,Ismail and Griersonl 1977j. Gol-erruneniregulations. consumel demand and environmeutal collcems in the lESt few years have iedtolesearch-on developing or improving non-chemical methods for irosthawest protectionofhorticultual crops (Schirra and D'hallewin, i997).

The aim of this investieation was to evaiuate the eflects qf hot water ffeatmentIFAVTy on \eepire qualin oI p-omegranate' ard Lo srud) whether rhe beneficial elfect ofib i . l redtTenl or

- re i luc i r ig Cl o f pornegranates could be compared \^ iLh cbemica l and

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\4ATERIA L5 AID ML THODSFresh pomegraaate ftuit were selected from the Agricultural Research Center of

Yazd province. Fruit were picked manually and immediatefy delivered to the laboratory.The following day fruit of uniform size were chosen at random. Damaged and inegularfrrit (those with sunburl, cracks, cuts and bnises in the husk) were removed and selectedfruit were randomly distributed into different lots. Pour replications of five firiit perreplication were used.

In 1997 'Maias Yazdi' and 'Malas Saveh' fi'nit were dipped in hot water (I{WT) at50 and 75"C (water bath model YCM-04M), imazalil (1 and 3 nd/L) and benzyladenine(80 and 100 mg/l) for 2 and 5 minutes. In 1998, 'Malas Yizdi' {iuit were dipped in hotwater at 35, 45, 55 and 65"C for 2 and 5 mirutes. In both yiars dipping in disiilled \.vaterat 25oC was the controi treatment. Followins treatment'the fruii wire dried at roomremperarure ard fioved to a sroraee room and-kepr for 4.5 monihs in che f;r.t lesl and jmonths ior the second one, at 1.5oC and 85+3% RII. Fruit were removed fiomrefrigerated storage and after 72 h at room. temperature -(2 5+3'C ), weight loss, elect olyeleakage, browning, and potassium ion leakage lsecond ye{r only; were measured as anindex of CI and ftuit quality. Twenq/ ftuit lfour replicatiohs of five fiuit per tueatment)were used lor each measurement.

Fruit weight loss was evaluated by weighing the fruii belore and after storage. Theamount of extemal (skin) browning was rated on a scale ff 0 (no browning), 1 (10%),2 (2s%), 3 (.so%), 4 ('7 s%) arLd s (ib0%).

To detemine the rate ol electuolyte leakage of peel tissue, 6 discs (10 mm) werecut rvith a cork borer. Conductiviry after incubation id 25 ml 0.4M mannitol wasmeasured with a conductivity meter (model series 0l 64{.; after 4 h incubation underconstant shaking. After readings were taken, the flasks weie autociaved at i ahn. (101.3kPa) pressure for 20 mirutes, held ovemight ard conductivity was measured again fortotal alectuolytes. The rate of ion leakage- was. expressed as a percentage of t1e total(initiavtotal)x 100 (McCollum and McDonald, 199i). nor deterrnining the late ofpotassium ion leakage, the incubation medium was prep{red as above and potassiumconcentrations measured with a flame photometer. Leakagd was expressed as the ratio ofthe 4 h leakage of potassium to total potassium leakage. lotal soluble solids (TSS) wasmeasured using a hand refractometer, TA (total acidity) wai detemined by titrating 10 mlofjuice with 0-.2 M NAOH (as citric acid) and pH uiirg a pH meter. Ascorbic aiid wasdetemined by employing the method described 6y Jacobs ({ 951).

Alalysis of Vaxiance (ANOVA) was calculated and mean s€paxations weredeiermined using Dirocao ' mulriple range resL ai p=0.05.

RESULTSH\,i/T at 75'C caused heat iniurv and led to dbcay, so thrs uearmenr was

elininated from fr.mher e\penmenrs.'The differences benr6en dipping for 2 and 5minutes in ai1 tueaments were not sistriflcant and thu! their combhed means arepresented.

Weight LossIn ihe hrst e:'periment. *eighi loss rnas leasr in rreared firl it u.i& FIWI ar 50"C

compared with other beatments ard the control (Fig. 1). In the second, the rate of weightloss increased with increasing hot water temperahte. blt there were no significanttreatment elfects up to 55"C (data not shown). it seems thht high weight loss at 65"C isrelated to heat injury. This result is consistent with previous work with kumquats (Schirraet al., 1995). They showed that IfWT at 53'C signifrcantly ieduced fruit weight ioss.

BrowningThe results of the first year for the dilferent treahlents were very different; skin

browaing was least in fruit treated with HWT at 50"C (Fig. 2). Other treatmentsdecreaseiL browling but the differences were not signjficani excelt for BA at 80 mg,&. In

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1ee8, H$'r at 45"c ,:g*:1:t1gi"#ft.TgJ13:[ffi,1n"'" -as slighr heat rnlury andindeased Percentage ol brownlng m

**""i'i::*:,"',f ?;*e: y:'ifl i*T:1v.,H:*:1i:,HYh?! :l;:,fl,f, "-J:ffi5:'Ji(i/1000), whereas other teatmentsi"","",]i,g the hot^walel.q1P::X',t#S"**",'*X"i,*:'"T1"-"il'H$'iffi11$?f;:tit"jJ:l;ili}T,'Jl}i'":i:';:6;;;11;;b;;"' and increase Jr""["ivi" 1"'"t"e"(Warg, 1990).

Potassium L€akage tassium- leakage was least in ftuit fieated with Hwr at 45'c' but the

**:' *ff'"i$,'iff:,n:i*Tir$: il;#:tand.skin.browning.*-"::-1gy,'l in 'Ma1as saveh',l'* 'lriuruiv-ii; ntil iaitu -ipt?ittt"aj This suggeits that 'Malas Yazdi' is more

*"niiti-,e "ultivar

to 1ow temperature dunng storage'

"t"tt "ffJi3*"r. no signiicant differences among treatments in TSS' TA' pH anrl

us"ort i. uiiA otruit after-storage (data not shown)'

DISCUSSTON h other fi.Ilir (Lude"^- - -itr" iesutts of the present study confirm previols results wrt

ft kff t;#j'f Hi:iffi :'ltil$q:i:";:i'di"i:r"r"{:i::i*i[hJJF]#*fr lli,.}Xffi ',"j1?i::m'""*f,,,nJi'#'1Sfl 3;i11iilH!f :;l58"C iojuled ftuit peel and increased CI

;#"T'+#t5ri:ttr'*Hl'uf ':,'*,fJ#::ti?::{T{t#id1t?iii,r"i"ii. rt i.'iiei;ti"a tnut tn"

'"ff""t of postha est leat^treaimen

:##t#ti:ir.::"r*imi:"f f, r*i'lY:j;nr-":?"iii^fTtrf; iJi'ry,'l;'&%?pomegrauate nlrt.

ACKNOWLEDGEMENTSThalksareextendedtoshilazUnivelsityfor|mancia.lsupporisandtotheHeadof

the .qeric;lhtral Research Center ofYazd province for providrng the pomegranales'

Literature CitedBadizadesan. A. and Khabbazlan , G.H. 1977 . Study.of pomegranate cultivation i]l FaIs

:;ffii;: S#;t"i:i"".ffi [J'"-*"r.' c""t"r, Publicatio.n No'7 u'.3oltf f;liiT];","'eurrn" i . , . i , - o .M. ; -Bu '1 . S. . Cr . "n . S and Wool l { B lqq7 ln ter r

treatmelts and controlled adosphere storage on qualitl of 'Fu1'u' persimmons'

"rl?iTTff] 3'1f ff."H"i 11 liaT Postharvest phvsiologv and storase behavior or

pomegranale f ru i t . . Scien, ia Hon. 24:287-2q8lsrnarr , V. A. and Lrr ierson,

" io j l . S." t* . ' suscepl ib i l iq ? l f l ip l* i '

ro chi ' l ing

,"..Rlo*1i"1""j'it [,r:il::l %3.xi"l:flF'",:"i"1]'''i"To'iiii;iisl rnLe"..i"n.e_ Publishers Inc. New York, USA.Lurie, S. anO Kfein, J.D. 199i. Acquisition of iolvJem-perarure l91.tt3ll:9 1o^iqtuto*

byerposure to h ;gh- iemperarure s ress J Amer . Soc Ho l l Sc l l lo : I uu - ru Lz '

889

Lit*s'^13:r$#friiif '*',-,."6:1"?.;'r*'f ff 53'":.i:ll,iil;iit;il'""-iljy;ilTl'*ilo:'"fi iT;'ii;X'1oi;l,Tl"3ii11;,X,l3J;,"1f Hii:!,:',aHi1-'-ffi {:1$,i{i;;,{;,i,,:?iil:1';;,1,ffi ligtith _l"i::Lf f :*;rI ;:"*tiri:

*g.v=$i{,',".'*ir",l#''llts;",1"'1Til11:;,3lFonunemandarinswaug (ed r, chlhng in:u,y orijli?"e"'#,yysi$"Js*3fli:iofls; nffi:oz. rn: c v

Figures

d

1

BA(ms/l)!1q9q !!!9q 50

lmazal i l (ml) HWf C)

Fig 1 Effect of beyJlll:"i". iBAl^imazalil and hot water (HW) on werght loss of fruitffi:##"1,'i::1","H:f,:*i;ifH?Jl l1lff.f,t'*i-#, corun s with a rJter

1 5

1 0

5

0

BA(ms/l)1/1000 3/1000 50 controt

lmazal i l ( . l l l ) HWfl C)

'.'ff::HH"Tr#i:1r"*!i*];.:?i3iffi f *:l#:hril'J"n1p*,if ""1H1i

890

fffect of di fferenr hot warer temperatures on fir-rit brow:

i"trg.lt i.jr i rs98 t. For each 'neatrnent'

colunus withg after 3 n.tonths ofletter ir col1llllon arc

rot significantly different at p:0 05'

807A00

40

30201 0

Ao 100 1/ 1000 3/1000

BA(mg/l) lmazalil(mi)

891

s1 0 0

80

60

40

20

0J5 45 55

Hot Water Temperatures(C)

Fig. 5. Effect of different hot water temperatures ou ion leakage of ft1rit after 3 months ofsrordge at t .5 .C tJq9gt . For each r . " r , , . . " , i ; ; t , , ; ; " : : , ; , - ' l :_"ot

,tg"ifi*otly diir"i*i ##;3;:""-ent' columns with a letter in colm''on are

r00s 8

Hot Water TemperaturesCC)

Fig- 6. Effecr of different hot water temp.eratures on.potassium ion leakage of firrit after 3months of storage at 1.5.Ccommon are not-signir;;y iiiri]."ixl i1ilotil"t""t columls with a letter in

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