Postharvest color development of strawberries: Influence of matunty, temperatare and light

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1 HORTCULTURE SECTON Pstharvest clr develpment f strawberries: nfluence f matunty, temperatare and light Can. J. Plant Sci. Dwnladed frm by n 5/3/18 r persnal use nly. W. Kalt, R.K. Prange and P.D. Lidsterl Agriailture Canada Research Statin, Kentville, Nva fttia B4N U5. Cntributin n. 214, received 22 June 1992, accepted 5 Nvember $a]t, W, Prange, R. K. and Lidster, P. D Pstharvest clr develpment f strawberries: nfluence f maturity, temperature and light. Can. J. Plant Sci. 73: Strawberries (cv. Blmidn) that were either cmpletely white r red at harvest were stred up t 8 d under varius temperature and light cnditins t examine the effects f strage cnditins n pstharvest clr develpment. Strawberries, stred at 5,1,2 r 3'C and at lighi levels f, 1 br 2 pml m2 t ', Y"P sampled fr anthcyanin cncentratin, surface clr,ital sluble slids, titratable acidity, ph f the berry surface, and berry weight lss after, l,2, 5 and 8 d f strage. Anthcyanin cncentratin and surface clr increased during strage with greater changes in the whiteharvested than redharvested fruit. Temperature, and t a lesser eitent light, affected tfie rate f strawberry clr develpment during strage. After 8 d, the prprtins f the tw majr strawberry anthcyanins, petargnidin 3glucside and cyanidin 3glucside, were different in redharvested fruit and white fruit that became red during strage, cmpared t fieldripened fruit at harvest. Key wrds: ragaria x ananassa, anthcyanin, strage Kalt, W., Prange, R. K. et Lidster, P. D D6velppement de la culeur des fraises aprs la reclte: influence de la maturit6, de la temp,6rature et dela lumiire. Can. J. plant Sci. 73: Des fraises de la vari6td Blmidn qui 6taient sit cmplbtement blanches, sit tutes ruges ir la cueillette, nt 6td_cnservdes jusqu'd huit jurs sus divers r6gimes thermiques et lumineux afin d'examiner les effets des cnditins de cnservatin sur la frmati6n de la culeur aprbs la r6clte. Les fraises cnserv6es e 5, 1, 2 u 3"C sus des dclairements de, 1 u 2 pml m2 s' nt 6t6 analys6es sur leur cncentratin d'anthcyanines, sur la culeur de surface, sur textrait sluble ttal, sur 'aiiditd titrable, sur le phde la surface du fruit et sur la perte de pids du fruit, au but de O,1,2,5 et 8 jurs de cnservatin. Les incentratins d'anthcyanines etla culeur superficielle augmentaient durant la cnservatin, les changements 6tant plus marqu6s chez les fruits r6cl[6s blancs queihez ceux r6clt6s ruges. La tempdrature, et dans une mindre mesure la lumidre, influaient sur le d6velppement de la culeur durant la cnservatin. Au but de 8 jurs, les prprtins des deux anthcyanines principales de la fraise, la p6largnidine 3glucside et la cyaniitin6 3glucside dtaient diff6rents dins les fruits r6clt6s_ rtlges et dans les fruits r6clt6s blanci qui avaient rugi durant la cnservatin, par rapprt avec les fruits mris sur pied au champ. Mts cl6s: ragaria x ananassa, anthcyanine, cnservatin Strawberries (ragaria x ananassa Duch.) can accumulate anthcyanin pigments after harvest. ruit that are harvested when nly 'Current address (P.D.L.): Agriculture Canada Research Branch, Sir Jhn Carling Building, 93 Carling Ave, Ottawa, Ontari, Canada KA C5. 25% red becme cmpletely red when stred fr 34 d at2l"c (Smith and Heinze 1958). Anthcyanin synthesis in strawberry fruit fllwing harvest can be used t imprve the appearance funderripe fruit; hwever, cntinued clr develpment during strage f red fruit culd be detrimental t clr quality. We have bserved that under certain cndi Can. J. Plant Sci. 73: (Apr. 1993) tins strawberries that are harvested fully red 541

2 CANADAN JOURNAL O PLANT SCENCE Can. J. Plant Sci. Dwnladed frm by n 5/3/18 r persnal use nly. will darken during strage, making the berry appear verripe, dull and less appealing. t is nt knwn whether this phenmenn is due t cntinued anthcyanin synthesis during strage. Tw anthcyanidin glycsides, pelargnidin 3glucside (Pg 3gl) and cyanidin 3glucside (Cy 3gl), are almst exclusively respnsible fr the red clr f strawberries (Timberlake and Bridle 1982). Under the acid ph cnditins f strawberry fruit, these tw pigments differ in their hue. Pg 3gl is rangered, while Cy 3gl is magenta in clr (Harbrne 1984). The prprtin fpg 3gl t Cy 3gl can vary amng gentypes f fieldripened strawberries fruit, but is generally abut 88% Pg 3gl (Wrlstad et al. 197). Since pstharvest clr develpment may r may nt be desirable, the fcus f this study was t investigate pstharvest cnditins which influence clr changes in underripe and mature strawberry fruit, and t examine the clr quality f strawberries harvested white r red, after cntrlled envirnment strage. MATERALS AND METHODS Experimental Material Strawberries (cv. Blmidn), either cmpletely red r cmpletely white, were harvested frm a cmmercial field in Nva Sctia and placed in varius strage treatmens within 4 h. The experiment was replicated by using berries harvested during the first and third week f Julv 199. Strage Cnditins The berries were stred in fur Cnvirn E8VH grwth chambers set at 5, 1, 2 and 3"C. Light was supplied by a cmbinatin f flurescent (75V) and incandescent (25%) surces. Light intensity was varied by using layers fblack screen abve the sample trays t prvide. l(d r 2 pml m's'. Light intensity was measured at the berry surface using a LiCr Ll1776 Slar Mnitr. Berry samples (+ 1 g) were cntained in clear, perfrated plyethylene bags t reduce misture lss. Berry temperature was cntrlled by placing the bags, with the perfratins facing upward, n a mesh screen held at the surface f a water tray. Air temperature inside bags held in the dark was.2'c (SEM.24) belw the set temperature, while bags stred at lfi) and 2 pml m' s' were 1.57C (SEM.2'14) abve the set temperature. ruit were sampled after harvest and after 1,2, 5 and 8 d f strage. Analytical Methds Surface clr f the strawberries was rated by the same persn thrughut the study, using a 5 scale with.5 increments. The ratings fr white, red and dark red berries were, 4, and 5, respectively. T determine the anthcyanin cntent fthe fruit, six t eight berries were cut int quarters, and the inner pith tissue f the receptacle was remved. The remaining material (1215 g) was blended fr 2 min in a Virtis Hmgenizer. ifteen g f l% frnic acid and l g f the fruit were blended fr 2 min, and vacuumfiltered thrugh Whatman N. 42 paper. A 2mL aliqut f filtrate was aded nt a Waters C16 SepPak cartridge (Waters, Mississauga ON) rinsed with 2 ml f water, and the anthcyanins were eluted with 2 ml f l% HC in prpanl. Samples were stred at 2'C until analyzed. HPLC separatin f strawberry anthcyanins was cnducted n a Beckman System Gld HPLC using a Beckman Ultrasphere ODS Cr8 clumn (4.6 mm x 15 mm) and a twslvent gradient elutin. Slvent A was 5% aqueus frmic acid and slvent B was methanl. A gradient elutin was achieved by varying the percentage f slvent A in the fllwing manner: 93V fr the first 2 min; decreased t 85V ver 6 min; decreased t 257 ver 17 min: decreased t 2O% ver 2 min. Slvent A was returned t 93% ver 2 min t reequilibrate the clumn. The eluate was mnitred at 52 nm. Since pure anthcyanin standards are nt cmmercially available, HPLC data were analysed as area units g W'. N crrectin was made fr differences in the mlar absrptivity f the tw pigments in acidified methanl (Pg 3gl e : 31 6; Cy 3el e = 29 ffi) (Wrlstad 1976). Sluble slids cntent (TSS, %) and titratable acids (TA, mg malic acid equivalents/lo ml juice) were measured injuice extracted frm the berries. The TSS was measured using a handheld' temperaturecmpensated refractmeter (Atag' Japan) and TA was measured using a semiautmatic MultiDsimat E4 5 titratr (Metrhm AG, Switzerland). The ph f the fruit surface was measured using a Sensrex cmbinatin ph electrde (Sensrex, Stantn, CA). Statistical Analysis Statistical analysis fthe data, after necessary transfrmatins, was cnducted using the analysis f

3 KALT ET AL. _ POSTHARVEST CHANGES N STORED STRAWBERRES 543 Can. J. Plant Sci. Dwnladed frm by n 5/3/18 r persnal use nly. variance prcedure in Genstat 5 (Payne 1987). Statistical tests were cnducted at P <.5. Plynmial regressin was used t describe respnses f the quantitative factrs t strage time. Cntrasts were used t cmpare the effects f temperature. Althugh the experiment was cnducted atne time, data btained n white and red berries were analysed separately. Anthcyanin area units g W' plus were transfrmed t the lg, scale t equalize the experimental variances amng factrial cmbinatins. Data btained at 5 and 1C were averaged because the respnses bserved at these tw temperatures were nt significantly different. r the same reasn data btained n berries stred under light intensities f lfi) and 2N p.ml m'2 s' have been averaged. RESULTS Effect f Temperdrne n Chr Develpment igure illustrates changes in the clr f whiteharvested and redharvested strawberrv =L E a E = 5 E 4{n :<' (L zt {: X U S am il r* 2 lrj! + C) 7xffi z, 6 z../t C: Red R2=76.7% srr/\ge DURATTON (DAYS) fruit during strage at varius temperatures fr up t 8 d. Results f regressin analysis f the curves in ig. are shwn in Table 1. Anthcyanin frmatin and changes in surface clr during the strage f whiteharvested strawberries (ig. 1A and B) depended n temperature and duratin f strage. When whiteharvested berries were stred at either 5 r 1C, there was an increase in anthcvanin cntent f22 area units g wr d1. At 2'C pigments accumulated rapidlv. with an increase f 996 area units g wt'at. At 3'c anthcyanins frmed mre slwly than at 2'C. At 3"C the rate f increase was 36 area units g wr d1. At the end f the 8d strage perid, berries held at 5 r 1"C were still nt cmpletely red in clr, i.e., surface clr rating < 4 while the 3 and 2O"Cstred berries had reached and exceeded a surface clr D: Red R2:83.5% 2 z. 1E E dc) 58 *E D gul ig. l. Changes in anthcyanin cncentratin (Panels A and C) and surface clr rating (Panels B and D) f whiteharvested and redharvested strawberries during strage at different temperatures. 5 and l'c; a 2"C;.. 3'C. Peak : Pk, : p"1*tnidin 3glucside, Peak 2 : Pkr : gt*tdin 3glucside.

4 544 CANADAN JOURNAL O PLANT SCENCE Can. J. Plant Sci. Dwnladed frm by n 5/3/18 r persnal use nly. Table l. Results f regressin analysis f data in ig. 1, using the equatin J : brt + b2t" + a,wherct : time (d), and a = day value Az Temp. 5 & 1'C 2"c 3"c SEMY 5 & ro'c 2"c 3'c SEM 5 & l"c 2"c 3'c SEM 5 & l'c 2"c 3'c SEM t4r b t9.447 za = anthcyanin cncentratin, whiteharvested berries; B : surface clr rating, whiteharvested berries; C = anthcyanin cncentratin, redharvested berries; D : surface clr rating, redharvested berries. vstandard errr f the mean with n = 12. df : 12. ratingf 4, respectively (ig. 1B). ncreases while abut 2t/ f the red berry samples in anthcyanin cncentratin were best cntained rtted berries. described by linear mdels, while changes in surface clr rating fit quadratic mdels rmatin f Pg 3gl and Cy 3gl in the (Table 1). Redharvested berries that were stred at either 5 r 1"C accumulated anthcyanins at a rate f abut 147 area units g Wl dr (ig. 1C) and surface clr rating increased frm 4 t 4.62 by the end f the 8d strage perid (ig. 1D). At 2'C and 3"C pigments accumulated at abut 48 area units g Wr dl and the surface clr rating f these berries increased frm 4 t apprximately 5, indicating a dark red, verripe appearance. The inhibitin f anthqcyanin frmatin bserved in the whiteharvested berries at 3'C was nt apparent in the redharvested berries. Like the whiteharvested berries, increases in anthcyanin cncentratin in redharvested berries fit linear mdels while changes in surface clr rating were described by quadratic mdels (Table l). Sme berries rtted during strage. Rt was nly bserved,at2 and 3"C, and after 5 d f strage. Apprximately 5% f the white berry samples cntained sme rtted berries, l6t).6' t r8 32r8 32r8 ield and in Strage Changes in the percent Pg 3gl during strage are shwn in Table 2. During the first 2 d that whiteharvested berries were held at 5 and 1"C nly a small amunt f Pg 3gl, and n Cy 3gl was detected. n white berries held at 2O and 3C. there was a cntinuus decline in the prprtin f Pg 3gl frmed (Table 2) while rapid anthcyanin synthesis was ccurring (ig. 1, A). Red fruit cntained 88.1% Pg3gl at harvest, and this prprtin stayed cnstant fr the 8 d when berries were held at 5 and 1C. Hwever, when red berries were held at 2 and 3'C there was a significant decline in the percent Pg 3gl after 5 d. Since pigment frmatin ccurred during this time (ig. 1C), the change in percent Pg 3gl reflects an increase in the prprtin f Cy 3gl synthesized. Effect f Light n Clr Develpment Light had little effect n the develpment f strawberry clr during 8 d f strage 4 A

5 KALT ET AL. POSTHARVEST CHANGES N STORED STRAWBERRES 545 Table 2. Percent f Pg 3gl as a functin f strage time, temperature and strawberry clr at harvest. Lg16transfrmed pigment ratis used fr statistical analysis are shwn in parentheses Can. J. Plant Sci. Dwnladed frm by n 5/3/18 r persnal use nly. Clr at harvest White "lgt6 rati f Pg 3gl/Cy 3gl as l916 (Pkr) Ystandard errr f the mean with n 12, df = 48. xn = 2, dav values were nt incl in statistical analysis. Table 3. Effect f light n Clr at harvest White Red Significant effects (P < z 5 8 * z 5 8 Light cnditins Darkx Light" Dark Light zsurface clr ratings f, 4, 5 vstatistical analysis was xdark;n:32.df=19. cnducted wlight included bth 1 and 2 "NS = nt significant, C = Clr rncrease f white in the light. (Table 3). There was a signi nly in the surface clr harvested berries after Effects f nitial Berrv Treatment n Strawberrv The effects f berry clr at duratin, temperature and li ph fthe berry surface, and are shwn in Table 4. Whi cntained siglificantly lwer higher levels fta than red Pg 3gl (7 f Pg 1l + Cy 3gl) 5 & 1"C 2 & 3"c 1. (1.3t2 1. (r.4) 91.4 (1.s) 92.5 (t.rd (.129) 88.l (.94) 88.5 (.9) 88.5 (.89) 88.3 (.89) 89.8 (.97) (.22) 94. (r.s4) 91. (1.3) 88.1 (.88) 84.4 (.73) (.129) 88.1 (.94) 88.9 (.92) 88.1 (.89) 86.s (.81) 84.s (.73) (.22) cncentratin and surface clr rating in whiteharvested and redharvested strawberries during strage Anthcyanin cncentratin Lg;6 areay 2.46 (.72) 2.59 (.s1) 3.63 (.r7) 3.63 (.12) NS" white, red, and dark red, respectively. l916 transfrmed values, SEM shwn in parentheses. m s, which were nt significantly different; n = 64, df = harvest, L = Light cnditins. and Strage Attributes, strage ON TSS. TA. t weight lss berries ftss and, and white Surface clr' (5) 2. (.88) 2.4s (.62) 4.49 (.61) 4.65 (.Or3) CXL berries never develped the levels ftss and TA bserved in red berries at harvest. Higher levels f TSS were bserved when white berries were stred in the light and at higher temperatures while titratable acidity remained at a higher level when white berries were held at lwer temperatures. The surface ph f white berries was lwer than red berries. Differences in the surface ph generally reflected differences in TA. Althugh differences were small, surface ph was higher when berries were stred at higher temperatures.

6 56 CANADAN TOURNAL O PLANT SCENCE Can. J. Plant Sci. Dwnladed frm by n 5/3/18 r persnal use nly. O H ' a a q u) a +. B\ Ov '6 J 8 b ad^!, bs q = 5e r.y,9.: JE n:f,o\o\ crq9 e{$$ Jc.i h\o O\ \nnq sc{n 6\ 6 6 X J i\oo\o hn n 6NO\ h :hcl\@ X :h N@i Ḟ rnn d;giaidi +E cidddci.^ *N \gnnn d\@ 8x8K x rh Ns nqc!cl n ds\ l alel.:gcl c_!nc) q.iqnq 666 Eqq qiqe :NOh Na.t\.iiicj nr@o n*nr rno nh\6 no\o\$ hn\ :::: :ij: iji: qqqq n\\h \ AO X X slhe{ N\ Ji.:.1 d n 6 adoh Y h\rh " iijjd r n1 q qnqq rhc^l \\\n \\n grviqi a rlc{ncl 9v?99 nd} qn +r b,1 n nnnqc{ nhhh hnnh hhs* nhhn *dh inh dc^lh6 da.lh@t v= =u /i"i (J d rq cn J.!) u) d T rh' *rr O ^ ilc "9 =.^5 =.: 5dv b rl q 9T ll.e EJ S ^tr 5 ts " H il= bt)o d p ^ tt'e s E.t.: f'e 3 =a.:l E O,,d ll ;: ='T trn *E ej : b.: E EnEiH.Y >Vii 'Er e k X E r_ " E?=EE= a _,e dl =Q HE'.. rl ib=;,5 uc) 6 r" N >x ' >

7 KALT ET AL. POSTHARVEST CHANGES N STORED STRAWBERRES Can. J. Plant Sci. Dwnladed frm by n 5/3/18 r persnal use nly. resh weight lss in whiteharvested berries was influenced nly by the presence r absence f light, and was nt significantly atrected S strage temperature. n red berries, hwever, fresh weight lss was affected by bth light and strage temperature. While weight lss f red berries stred at lw temperatures in the dark was abut 1.69%, it increased almst threefld in the light t 4.89%. After 8 d in the light, weight lss was abut threefld greater at high temperatures (13.88%) than at lw temperatures (4.89%). All f the quality attributes examined were affected by strage duratin. DSCUSSON Effect f Ternperature n Clr Develpment Althugh the respnses t light and temperature bser,ved in the present study were similar t thse reprted in earlier studies (Smith and Heinze 1958; Austin et al. 196) there were als distinct differences. n Sparkle, a strawberry cultivar suited fr the same gegraphical regin as Blmidn (Galletta and Bringhurst 199) a psitive respnse f pigment frmatin t temperatures between 13 and 29C was bserved (Austin et al. 196). They reprt that clr frmatin at29"c is significantly greater than at 18C, and these temperaturedependent differences are readily apparent after 12 h f strage. n the present study, bth anthcyanin measurements and subjective clr ratings f berries indicated less pigment frmatin at 3 than at 2"C. which was apparent after24 h fstrage. Results fthe tw studies were similar at the lwer strage temperatures. Austin et al. (196) reprt that clr frmatin in white berries held at 13'C was nt cmplete after 4 d while in ur study red clr develpment in white berries held at 5 and 1C was still incmplete after 8 d f strage. rmatin f Pg 3gl and Cy 3gl in the ield and in Strage n a study f 18 different strawberry gentypes, the mean ttal anthcyanin cncentratin was 573 p.m gl and mean percentage f Pg 3gl was 88% (Wrlstad et al. 197). n the present study, fieldripened Blmidn berries had the same prprtin f Pg 3gl at harvest, i.e.,88%. The surface clr ratings f whiteharvested berries were influenced mre by the percent Pg 3gl than by the abslute anthcyanin cncentratin. After 8 d the percent Pg 3gl and the surface clr rating were similar at 2 and 3"C (Table 2) (ig. lb), althugh the abslute anthcyanin cntent fthe berries differed by 2.6fld (ie. 1A). While benies held at 5, l and 3'C had a similar anthcyanin cntent (ig. 1A) bth the percent Pg 3gl and the surface clr rating were different between these samples (Table 2) (ig. 1B). The percent Pg 3gl decreased during pigment frmatin in strage i.e. a higher prprtin f Cy 3gl was synthesized after harvest than under field cnditins (Table 2). Since Cy 3gl is a deeper, magentared cmpared t the rangered f Pg 3gl, the higher prprtin Cy 3gl may cntribute t the higher surface clr rating indicative fdark berries. Effect f Light n Clr Develpment The minimal effect f light bserved in the present study was generally cnsistent with earlier results. n the strawberry cv. Sparkle, Austin et al. (196) nte a small effect f light n the rate f pstharvest clr develpment at29"c while the effect is negligible at l3'c. n cntrast, we bserved that light increased the surface clr rating f white berries and, alttrugh nt statistically significant, the effect was greater at lw than at high temperatures (data nt shwn). Effects f nitial Berry Clr and Strage Treafinent n Strawberry Quality Attributes Our results, like earlier studies, demnstrate that althugh unripe berries becme red during strage, they d ntunderg sufficient changes in sugar and acid cntent t be suitable fr fresh cnsumptin. Hwever, results frm an infrmal taste panel (Smith and Heinze 1958) indicate that underripe strawberries that turn red after harvest are

8 548 CANADAN JOURNAL O PLANT SCENCE Can. J. Plant Sci. Dwnladed frm by n 5/3/18 r persnal use nly. acceptable if sugar is added. Althugh this may be useful when berries are destined fr prcessing it is f n use fr strawberries intended fr fresh cnsumptin. ncreasing ph decreases the clr intensity f anthcyanin pigments (Jackman et al. 1987) althugh in the present study the range f berry surface ph values (3.3.6) was prbably t small t cntribute significantly t phdependent clr changes in surface pigments. The highest surface ph values, where anthcyanin clr wuld be least intense, were bserved in redharvested berries that had becme deep red after 8 d f strage (ig. ld) (Table 4). Weight lss was particularly high when berries were stred at high temperatures in the light. The mean temperature elevatin due t the lights was 1.57C with n difference in the amunt f heating between the tw liqht intensities (i.e. 1 and 2 pml m's'). Water lss can create mrphlgical changes that will affect clr quality. Changes in cellular cmpartmentatin as a result f water lss may give rise t anthcyanin xidatin, cpigmentatin, r metal chelatin (Jackman et al. 1987); all f these reactins can affect anthcyanin clr. Thus the deepening f red clr bserved in this study may be due in part t an increased prprtin f Cy 3gl. Hwever, it is likely that ther changes in the chemistry f the strawberry surface anthcyanins als cntribute t the lss f ptimal berry clr during strage. ACKNOWLEDGMENTS The authrs gratefully acknwledge the statistical advice f K. B. McRae and the technical assistance f L. Hamiltn, P. Harrisn and J. McDnald. Austin, M. E., Shutak, V. G. and Christpher' E. P Clr changes in harvested strawberries. Prc. Am. Sc. Hrtic. Sci. 75: Galletta, G. J. and Bringhurst, R. S Strawberry management. Pages ing. J. Galletta and D. G. Himelrick eds. Small fruit crp management. PrenticeHall, New Jersey. Harbrne, J. C. 19E4. Anthcyanins. Page 64 in Phytchemical Methds. Chapman and Hall, l,ndn, U.K. Jackrnan, R. J., Yada, R. Y., Tung, M. A. and Speers, R. A Anthcyanins as fd clrants a review. J. d Bichem. ll: 2r247. Payne, R. W. (Chairman, Genstat Cmmittee) Genstat 5 reference manual. Clarendn Press. Oxfrd. U.K. Smith, W. L. and Heinze, P. H Effect f clr develpment at harvest n quality f pstharvest ripened strawberries. Prc. Am. Sc. Hrtic. Sci. 72: Timberlake, C.. and Bridle, P Distributin f anthcyanins in fd plants. Page 137 in P. Markakis, ed. Anthcyanins as fd clrs. Academic Press, New Yrk, NY. Wrlstad, R. E Clr and pigment analyses in fruit prducts. Statin Bulletin 624. Agricultural Experiment Statin, Oregn State University, Crvallis, OR. Wrlstad, R. E., Putnam, T. P. and Varseveld' G. W Clr quality f frzen strawberries: Effect f anthcyanin, ph, ttal acidity and ascrbic acid variability. J. d Sci. 35: