Rpid Reduction in Arom Voltiles of Pcific Rose Apples in Controlled Atmospheres H.J. Tough nd E.W. Hewett Centre for Posthrvest nd Refrigertion Reserch Institute of Nturl Resources, Mssey University Plmerston North New Zelnd R.U. Redy Deprtment of Pomology Centre of Physiologicl Studies Hstings New Zelnd Keywords: Mlus domestic, voltiles, sensory evlution, ethyl esters, cette esters, ldehydes, lcohols, fruit qulity Astrct Arom voltiles mke n importnt contriution to the flvour nd eting qulity of pples (Mlus domestic). While controlled tmosphere () storge reduces the rte of decline of fruit qulity ttriutes such s texture nd colour, it lso reduces flvour fter prolonged storge. When Pcific Rose pples ( new cultivr recently developed in New Zelnd) were plced in (.% O 2 +.% CO 2 ) t. C, significnt decreses in rom voltile concentrtions occurred within weeks compred to fruit in regulr ir (). The mgnitude of rom voltile suppression y incresed with storge time nd with susequent shelf life t 2 C nd ws not reversile on trnsfer to ir. After weeks in, concentrtion of utyl cette, key rom voltile compound, ws only % tht in ; fter weeks there ws no utyl cette in fruit whilst high concentrtions (8 mm L - ) remined in fruit. Despite the lrge reduction in rom voltile concentrtions n untrined tste pnel found only slight reduction in flvour intensity nd no undesirle flvours in fruit. Conversely, some pnellists identified n off-flvour in stored fruit tht incresed s storge nd shelf life time incresed. Significnt differences in rom voltile concentrtions etween nd stored fruit my hve commercil implictions for consistency of flvour nd qulity etween lines of Pcific Rose pples. INTRODUCTION Controlled tmosphere () storge llows pple industries to store fruit for up to 2 months. Such fruit remin reltively firm with good externl ppernce ut consumers re recognising tht it is not truly fresh. Some cultivrs sustin mjor reductions of rom voltiles on removl to ir fter -6 months in storge (Streif nd Bngerth, 988; Mttheis et l., 99; Yhi, 99). Mesurle reductions hve een noted fter -2 weeks. The extent nd speed of recovery of rom voltile production fter vries with oth cultivr nd storge time with totl suppression nd lck of recovery reported for McIntosh pples fter 2 dys in (Lidster et l., 98). Pcific Rose is new pple cultivr from Gl Splendour cross, tht is ecoming populr interntionlly. It hs good storge potentil, mintining firmness throughout extended periods in ir t C (J.W. Johnston nd E.W. Hewett, unpulished results). The ojective of this work ws to compre rom voltile production from this cultivr fter storing in ir nd for up to weeks. MATERIALS AND METHODS Pcific Rose pples (count size 88, verge weight 2 g) were hrvested t commercil export mturity, pcked into 8. kg crtons nd plced into commercil coolstore in ir or in (.% O 2 +.% CO 2 ) t. C. After,, 8 nd weeks fruit ws removed to 2 C shelf life conditions prior to qulity determintion nd extrction of voltile compounds from expressed pple juice using diethylether: n-pentne (2: v/v) s solvent (Dixon nd Hewett, 2). Anlysis of rom voltiles ws undertken y injecting μl of concentrted juice into Hewlett Pckrd gs
chromtogrph Model 8 (Dixon nd Hewett, 2). An untrined pnel of people, () used Tringle Difference procedure to determine if difference existed etween three smples provided when two of them were from the sme tretment; (2) were sked to identify the rom detected, sed on pulished pple rom descriptors; nd () indicted their preferred smple from the three provided. RESULTS AND DISCUSSION Totl voltile concentrtion, comprising 28 mesured components (8 lcohols, ldehydes nd 6 esters) nd mesured 2 h fter removl from. C to 2 C, remined constnt in ir stored fruit throughout weeks storge. In contrst totl voltiles in stored fruit decresed from out 2 mmol L - initilly to. mmol L - fter weeks, decresing y 2,, nd 86% fter,, 8 nd weeks respectively (Fig. ). One dy fter removl from C to 2 C totl voltiles from fruit declined s time in storge incresed ut remined constnt or incresed through dys shelf life (Fig. 2). In contrst totl voltiles declined drmticlly in fruit, oth with time t. C nd through dys t 2 C. Recovery of voltile production occurred fter storge, especilly fter 8 nd weeks, ut not in fruit. Alcohol Alcohols showed the sme overll pttern s totl voltiles for oth nd fruit. Becuse lcohols re importnt precursors of esters in pples (Dimick nd Hoskin, 98), ny reduction in concentrtion will ffect rom voltile concentrtions.. Ethnol. Ethnol contriuted vrily (-8%) to totl lcohol concentrtion in fruit, hving similre ptterns of chnge during shelf life fter removl from oth nd storge (dt not shown). Concentrttion declined s time in incresed. 2. Butnol. Butnol concentrtions vried from to 6% of totl lcohol concentrtion in fruit from oth nd tretments. Presence of this lcohol is criticl ecuse it is precursor of utyl esters so importnt in rom development (Dimick nd Hoskin, 98). Butnol in. Butnol concentrtions remined reltively constnt during shelf life following removl from fter nd weeks, ut incresed 2 to fold on removl fter 8 nd weeks (Fig. ). Butnol in. Butnol concentrtions in fruit were much reduced compred with fruit t ll removl times from coolstore nd during susequent shelf life. After 8 nd weeks concentrtions were negligile (Fig. ). This progressively incresing reduction in utnol concentrtion from s erly s weeks in stored fruit, together with the inility to recover when returned to ir, suggests tht expected ttse nd flvour might to reduced to less thn cceptle levels. Acette Butyl cette concentrtions from fruit did not chnge consistently t. C remining etween.6 nd.2 mmol L - ; during shelf life t 2 C there ws slight initil decline efore concentrtions incresed through dys with the lrgest increse occurring fter weeks (dt not shown). In fruit t. C utyl cette decresed more thn 6% fter weeks nd ws only just detectle fter weeks, declining further to very low concentrtions t 2 C fter ll removls. Esters Totl esters in fruit decresed slightly with time t. C, remining constnt or incresing fter trnsfer to 2 C especilly fter 8 nd weeks. fruit showed sustntil nd progressive decline of totl esters t. C; this continued on trnsfer to 2 C with no recovery on trnsfer to ir even fter only weeks in (Fig. ). Sensory Evlution An untrined pnel of people ws used in n ttempt to relte ojective GLC
mesurements of rom voltiles to sensory nd preference scores for fruit from nd storge. There ws no difference in preference etween tretments for fruit evluted fter dys t 2 C following weeks t. C, ut fter dys fruit ws preferred (Tle ). After weeks fruit ws preferred. CONCLUSIONS Significnt nd irreversile reductions of some compounds tht contriute to pple rom nd flvour occurred within weeks in storge. It is possile tht such rpid nd non-reversile effect of on voltile production could occur even sooner thn weeks.. Although similr decreses hve een shown to occur within 6- weeks of exposure to (Lidster et l., 98; Ptterson et l., 9) most reports determine the effect fter -9 months storge. Alcohols, ldehydes nd esters ll decrese with time in reltive to storge. The inility of fruit to produce these compounds on return to ir t mient tempertures fter storge, indictes tht their iosynthesis is impired y. Thus the potentil exists for consumer resistnce to develop when fruit tht ppers to e fresh (firm nd juicy) on removl from, is found to hve sustntil flvour reduction on consumption. An untrined tste pnel preferred fruit to fruit fter weeks storge. This pprent disprity etween ojective nd sujective ssessments of qulity demonstrtes the difficulty in determining specific quntittive qulity ttriutes, such s concentrtions of totl or prticulr esters, in isoltion from the overll perception of qulity determined when tsting. It is lmost impossile for untrined pnellists to isolte the influence of firmness nd juiciness from rom nd flvour when mking their judgements. This difficulty is common prolem when compring sujective nd ojective methods of qulity ssessment (Mttheis nd Fellmn, 999). Tht such drmtic nd irreversile reductions in rnge of rom compounds nd their precursors occur following such short periods of exposure to suggests tht efforts should e intensified to develop prcticl techniques to llevite or reverse the undesirle chnges. Dynmic tmosphere storge (Mttheis et l., 998) or hypoxic tretments (Dixon nd Hewett, 2) undoutedly hve potentil to reduce loss of flvour voltiles induced y. In ddition plnt reeders should expose dvnced selection lines of fruit to storge prior to finl relese to ensure tht new releses do not hve uncceptle flvour loss when mintined in storge. ACKNOWLEDGEMENTS Thnks to ENZAFruit New Zelnd for finncil ssistnce nd Jonthn Dixon for technicl dvice. Literture Cited Dimick, P.S. nd Hoskin, J.C. 98. Review of pple flvour-stte of the rt. Crit. Rev. Food Sci. Nutr. 8:86-9. Dixon, J. nd Hewett, E.W. 2. Hypoxic tretments lter voltile concentrtion of pple cultivrs. J. Sci. Food Agri. (in press). Lidster, P.D., Lightfoot, H.J. nd McRe, K.B. 98. Production nd regenertion of principl voltiles in pples stored in modified tmospheres nd ir. J. Food Sci. 8:-2.. Mttheis, J.P., Buchnn, D.A. nd Fellmn, J.K. 998. Voltile compounds emitted y Gl pples following dynmic tmosphere storge. J. Amer. Soc. Hort. Sci. 2:-2. Ptterson, B.D., Htfield, S.G.S. nd Knee, M. 9. Residul effects of controlled tmosphere storge on the production of voltile compounds y two cultivrs of pples. J. Food Sci. Agri. 2:8-89. Streif, J. nd Bngerth, F. 99. Production of voltile rom y Golden Delicious pple fter storge for 2 yers in CO 2 nd O 2 tmospheres. J. Hort. Sci. 6:9-99.
Tles Tle. Influence of hrvest methods on scoric cid, NO -N, chlorophyll content of lef lettuce. Hrvest method Ascoric cid (mg/ g FW) NO -N (ppm) Chlorophyll z Reping y 2.2 8. Conventionl 2 2.92 9. NS x NS NS z Mesured with SPAD-2 (MINOLTA). y Dt from 2 nd reping hrvest. x NS, not significnt (P>.). Tle 2. Effects of loction nd cultivr on the vegettive growth prmeters of Jeruslem rtichoke in 998 nd 999 seson. Source: Jones et l., 99. 998 999 Loction Cultivr Cultivr Fuseu Locl Men Fuseu Locl Men Plnt height (cm) El-Kluoi 2. c 2.2 82. A. 2. 9.2 A El-Behir 8.8 c 2.2. B 2.2 c 6.8.9 B Men 2.2 B.2 A.9 B 96.9 A Min shoot dim. (cm) El-Kluoi.2.6. A... A El-Behir.2.. A.6..9 A Men.2.6 A. B. A No. min shoots per plnt (ech) El-Kluoi 9..8 8. A... A El-Behir.2. 6. A.8.2.2 A Men. A. A. A. A. A Fresh wt. (g/plnt) El-Kluoi.. 2. A.6 2.9 2.2 A El-Behir.6 2.. B... B Men. B.6 A. B.9 A Mens seprtion t % level (DMRT); cpitl letters etween men vlues, smll letters etween loction vlues.
Figures Totl Voltiles (mmol L - ) 2 2 8 Fig.. Totl voltiles from juice of Pcific Rose pples fter storge in nd for up to weeks t C. Totl Voltiles Totl Voltiles (mmol L - ) 2 (mmol L - ) 2 8 8 Fig. 2. Totl voltiles in Pcific Rose pples during dys shelf life t 2 C fter storge in or for up to weeks t. C.
2 weeks 2 weeks 8 6 2 2 6 8 2 Butn--ol (μ mol. L - ) 8 6 2 2 6 8 2 ( 2 8 weeks 2 weeks Butn--ol (μ mol. L - ) 8 6 2 2 6 8 2 Butn--ol (μ mol. L - ) 8 6 2 2 6 8 2 Fig.. Butnol concentrtions in juice of Pcific Rose pples through dys t 2 C following storge for up to weeks in or t. C. 2 2 Esters (mmol L - ) 8 6 Esters (mmol L - ) 8 6 2 8 2 8 Fig.. Totl ester concentrtion in juice of Pcific Rose pples fter removl from nd storge t. C nd during dys t 2 C.