To study the effects of different levels of preharvest shading (74, 58, 48, 38 and 5% of light penetration which were

denoted by So' SI' S2' 53 and S4 respectively) on developing strawberry (Fragaria X ananassa Duchesne) cv. Ostara

fruits, some chemical tests (pH, total soluble solids and titratable acidity) associated with fruit quality were carried out.

Results showed that although the different levels of preharvest shading were found to demonstrate a significant effect on

the chemical parameters studied, this could only be detected in fruits shaded by S4 and S3. However, for total soluble

solids, significant interactions were observed between location of fruit and fruit type and also between storage day and

fruit type

Osman, Azizah

Peter B., Dodd

Universiti Putra Malaysia Institutional Repository

PertanikaJ. Trap. Agrie. Sci. 17(1): 65-71 (1994) ISSN: 0126-6128© Universiti Pertanian Malaysia PressEffects of Different Levels of Preharvest Shading on the Storage Quality ofStrawberry (Fragariax ananassaDuchesne) cv.OstaraII. Chemical CharacteristicsAZlZAH B. OSMAN AND PETER B. DODDIFaculty ofFood Science and BiotechnologyDepartment ofFood Science,Universiti Pertanian Malaysia43400 UPM Serdang, SelangorDarul Ehsan, MalaysialWye CollegeUniversity ofLondonAshford, Kent TN25 5AHEnglandKeywords: preharvest shading, strawberry fruit, storage quality, chemical characteristicsABSTRAKUntuk mengkaji kesan penaungan sebelum tuai yang berlainan (74, 58, 48, 38 dan 5 % penembusan cahayayang dilambangkan sebagai So' 51' S2' S3 dan S4 masing-masing) ke atas buah strawberi (Fragaria x ananassaDuchesne) cv. Ostara yang sedang membesar, beberapa ciri ujikaji kimia (pH, jumlah pepejallarut dan keasidantertitrat) yang berkaitan dengan mutu telah dijalankan. Hasil kajian menunjukkan walaupun darjahpenaungan yang berlainan ini memberi kesan yang bererti ke atas ciri-ciri kimia yang dikaji, perbezaan inihanya boleh dikesan pada buah yang dinaungi oleh S4 dan S3' Walau bagaimanapun, bagi jumlah pepejallarut, keputusan menunjukkan wujudnya interaksi yang bererti di antara lokasi dan jenis buah dan juga diantara hari penyimpanan dan jenis buah.ABSTRACTTo study the effects ofdifferent levels ofpreharvest shading (74, 58, 48, 38 and 5 % of light penetration which weredenoted by So' SI' S2' 53 and S4 respectively) on developing strawberry (Fragaria X ananassa Duchesne) cv. Ostarafruits, some chemical tests (pH, total soluble solids and titratable acidity) associated with fruit quality were carried out.Results showed that although the different levels ofpreharvest shading werefound to demonstrate a significant effect onthe chemical parameters studied, this could only be detected in fruits shaded by S4 and S3. However, for total solublesolids, significant interactions were observed between location offruit andfruit type and also between storage day andfruit type.INTRODUCTIONPart I (Osman and Dodd 1994) reported on a studyof the effect of different levels of preharvestshading on the physical attributes of postharvestquality of strawberry cv. Ostara. Part II now de-scribes changes in the chemical characteristicsassociated with postharvest quality.The taste of sweetness and sourness is dueprimarily to the balance between sugar and wa-ter-soluble acid content (Huelin 1961; Moore andSistrunk 1980). In the strawberry, a proper bal-ance of these quality components not only pro-duces the desired level of sweetness, but also en-hances other flavour components (Moore andSistrunk 1980). The latter are responsible for thetypical strawberry taste (Went 1957). Sugar formsa high proportion ofsoluble solids (Huelin 1961).Soluble solids content and acidity appear tobe fairly consistent among cultivars (Scott andLawrence 1975). Variations are mainly due tomaturity, date of harvest and other field factors.Went (1957) pointed out that the sugar contentAZIZAH B. OSMAN AND PETER B. DODDis entirely a function of the light intensity to whichthe plants are subjected during the day and is in-dependent of the photo- or nyctotemperature.However, he reported that the development of thearomatic substances or flavour componentsrequires only a short period (not more than twohours daily) of high intensity light at low tem-perature and that the lower the phototem- perature,the stronger the taste. Many res- earchers havepointed out that citric acid is the dominantorganic acid in strawberry fruit (Whiting 1958;Markakis and Embs 1964; Sistrunk and Cash1973). They expressed percentage of titratableacidity as percent- age of citric acid. However, inthis study, since no attempt was made to determinethe dominant acid found in this strawberry variety,titratable acidity was expressed as ml of 0.1 MNaOH used per 6 ml fruit juice (Shaw et al. 1987).This experiment was carried out to study the effectsofdifferent levels ofpreharvest shading from flow-ering to harvest on the changes in the chemical(pH, total soluble solids and titratable acidity)characteristics associated with postharvest qual-ity of strawberry fruits.MATERIALS AND METHODSPlanting Materials and Fruit SourceThe experiment was conducted at Wye College,University ofLondon, England. The experimentaldetails pertaining to the preharvest shadingtreatments and experimental design werereported earlier (Osman and Dodd 1994). Fivelevels of preharvest shading of 74,58,48, 38 and5% light penetration (denoted as So' SI' S2' S3 andS respectively) were employed by covering thes:rawberry plants with netting of different levelsof light penetration. The three fruit types(primary, secondary and tertiary) under thesedifferent levels ofpreharvest shading were furthersub-divided into above (completely exposed) andbelow (hidden by leaves) indicating their location.The ripe fruits were harvested 32 ± 2 days afteranthesis.The same fruits, ten of each type (primary,secondary and tertiary) from each treatment andreplicate used for the determination offruit firm-ness (Osman and Dodd 1994) were used for thedetermination of total soluble solids, pH and ti-tratable acidity of the fruits. The punctured fruitswere immediately placed in labelled plastic bagsand stored in a freezer (-80°C) for the determina-tion of the above chemical characteristics.Total Soluble SolidsThe frozen strawberry fruits were thawed at am-bient condition before crushing with a pestle ina mortar. The juice was squeezed through fourthicknesses of cheesecloth (Duewer and Zych1967; Shaw et al. 1987). Total soluble solids (TSS)of the expressed juice (15°C) were determinedusing a hand refractometer (Bellingham andStanley model). Readings are presented in °Brix.pH of Fruit JuiceThe pH of the strained strawberry fruit juice wasdetermined with a pH meter (Beckman Model3500 Digital). Before each observation the accu-racy and sensitivity of the pH meter were checkedusing standard solutions of pH 4 and 7.Titratable AcidityJuice from the fruit sample was passed throughfour layers of cheesecloth. Six ml of the expressedjuice was diluted to 50 ml with distilled water andtitrated with 0.1 M NaOH to pH 8.2, with a pHmeter (Beckman Model 3500 Digital). The analy-sis was done in duplicate. Titratable acidity wasexpressed as ml of 0.1 M NaOH used per 6 ml offruit juice (Shaw et al. 1987).RESULTSThe ANOVA table in Table 1 shows the effect ofdifferent levels of preharvest shading, location offruit, fruit types, storage time (days) and theirinteractions on total soluble solids, pH and titrat-able acidity of strawberry.Total Soluble SolidsThere was a significant response of total solublesolids content of the fruit to the different levelsofpreharvest shading (Table 1). The total solublesolids content was found to decrease with a de-cline in the percentage light penetration reach-ing the plants and fruits (Table 2). Fruits underS which showed the lowest value were signifi-4cantly different from fruits of the other levels.However, fruits under So' S1 and S2 did not showany significant difference.Total soluble solids content also showed asignificant increase with storage time (Table 2).Location offruit alone did not affect total solublesolids content. Total soluble solids content wasalso found to be unaffected by the different fruittypes (Table 2). Nevertheless, there was signifi-66 PERTANIKAJ. TROP. AGRIC. SCI. VOL. 17 NO.1, 1994EFFECTS OF PREHARVEST SHADING ON STRAWBERRY - II. CHEMICAL CHARACTERISTICSTABLE 1Mean squares of the analyses of variance of three parameters of strawberry fruitsas influenced by different levels of preharvest shading.Source of df Total Soluble pH Titratable AcidityVariation Solids (ml of 0.1 M NaOH(OBrix) per 6 ml fruit juice)Shading (S) 4 99.9979** 1.2562** 76.122**Error a 8 2.1170 0.0351 5.396Location (L) 1 0.0271 0.0055 0.738SxL 4 0.8192 0.0077 1.437Error b 10 0.7743 0.0078 1.331Day (D) 2 15.8082 0.0952* 41.853**SxD 8 0.3569 0.0310 0.170LxD 2 0.0040 0.0109 2.052SxLxD 8 0.4399 0.0076 0.212Error c 40 0.5590 0.0232 1.438Fruit (F) 2 1.2760 0.1140* 2.052SxF 8 1.2332 0.0234 1.882LxF 2 3.8028** 0.0064 0.145DxF 4 2.2438** 0.0474 0.497SxLxF 8 0.7537 0.0277 2.308SxDxF 16 0.4670 0.0209 1.638LxDxF 4 0.5480 0.0221 0.672Error d 124 0.4288 0.0234 1.397Total 252*, ** are significant at 5% and 1% levels respectivelycant interactions between shading and fruit type,location of fruit and fruit type and storage timeand fruit type (Figs. Ia-lc). Primary fruits thatwere hidden (below) by the leaves had a lowertotal soluble solids content than the exposed(above) fruits (Fig. Ib). However, the reverse wastrue for the tertiary fruits. At day 0, total solublesolids content of tertiary fruit was lower than thatof primary fruits (Fig. Ic) but the reverse was trueat day 4.pH of Strawberry FruitJuiceIt was found that pH of fruit juice increasedsignificantly with decreasing percentage of lightPERTANIKAJ. TROP. AGRIe. SCI. VOL. 17 NO.1, 1994 67AZlZAH B. OSMAN AND PETER B. DODDTABLE 2Mean values for pH, total soluble solids and titratable acidity of strawberry fruits.MajorEffectTotal SolubleSolids(OBrix)pHTitratable Acidity(ml of 0.1 M NaOH/per 6 ml fruit juice)Shading (S)So (Control) 8.48 3.40 9.36SI 8.08 3.46 8.82S2 7.93 3.47 8.76S3 7.45 3.52 8.34S4 5.04 3.82 6.25LSDo.05 0.65 0.08 1.03Location (L)A 7.39 3.53 8.34B 7.49 3.53 8.32LSDo.05 NS NS NSDay (D)0 7.02 3.54 7.732 7.34 3.56 8.124 7.96 3.50 9.15LSDo.05 0.23 0.05 0.36Fruit (F)F I 7.53 3.56 8.45F2 7.30 3.49 8.28F3 7.27 3.55 8.27LSDo.05 NS 0.05 NSGrand Mean 7.42 3.53 8.32FI, F2, F3 are primary, secondary and tertiary fruits respectively.A and B are above and below (location of fruit) respectively.So' SI' S2' S3 and S4 are 74, 58, 48, 38 and 5% light penetration respectively.Day 0, Day 2 and Day 4 are 0, 2 and 4 days after harvest.NS - Not Significant.penetration from So to S4 (Table 2). However, nosignificant differences were detected betweenpreharvest shading levels So to S2' This suggeststhat pH of fruit juice is only affected whensubjected to a very low level oflight intensity suchas S3 and S4'Location of fruits under the preharvest shad-ing did not affect pH. The pH was found to beaffected by storage time, whereby a significant de-crease could only be observed between day 2 andday 4 (Table 2). A significant difference was foundbetween secondary and the other fruit types butnot between primary and tertiary fruits. None ofthe interactions were found to be significant(Table 1).68 PERTANlKAJ. TROP. AGRIC. SCI. VOL. 17 NO.1, 1994EFFECTS OF PREHARVEST SHADING ON STRAWBERRY - II. CHEMICAL CHARACTERISTICS•~9,----------------------,mo~10'----------------------'moLOCATION OF FRUIT--- LOCATION A ·M· LOCATION BFig.1bTitratable AcidityFruit titratable acidity was found to decrease sig-nificantly with decreasing percentage light pen-etration reaching the plants and developing fruits(Tables 1 and 2). However, no significant differ-ence was detected in the fruits shaded within therange of S1 to S3'Fruit titratable acidity was also found to in-crease significantly during the storage time. Byday 4, mean titratable acidity increased signifi-cantly (18.36%). The results in Table 1 indicatedthat titratable acidity of fruit juice was only sig-nificantly affected by very low levels of preharvestshading and storage time. All the other factorsand interactions were not significant.DISCUSSIONThe chemical characteristics (pH, total solublesolids and titratable acidity) measured in this studywere influenced significantly by the different levelsof light penetration reaching the plants anddeveloping fruits. There was a significant decreasein total soluble solids and titratable acidity withdeclining percentage light penetration from So toS4' Nevertheless, there was a significant increasein pH as the light intensity decreased. Thesefindings confirm the observations that shadingreduces soluble solids in apples (Heinicke 1966;Seeley et ai. 1980; Robinson et ai. 1983; Morgan etai. 1984) and in sweet cherries (Ryugo and Intrieri1972; Patten and Proebsting 1986). The findingsof these researchers and those of the presentstudy are, however, in contrast to what has beenstated by Sistrunk and Moore (1983). Theymentioned that soluble solids are related to fruitsize, being higher in smaller fruit within a cultivar.This is due to smaller cell size and compactnessof fruit as well as greater density.Nevertheless, results of fruit titratable acidityobtained in the present study were in contrast tothose reported by Robinson et ai. (1983) whofound that fruit total acidity correlated negativelywith percentage light penetration. As fruit rip-ens, starch levels decrease and soluble solids in-crease with the conversion of starch to sugar(Olsen and Martin 1980). Robinson et al. (1983),however, found that fruits from unshadedbranches contained both greater solids andstarch reserves than shaded fruits, in addition toa greater percentage of dry matter. Theysuggested that the effects of light environmentdo not seem to be due only to advanced maturity--------- -- ~ ----~-FRUIT TYPE--- FRUIT 1 .. FRUIT 2 .". FRUIT 3Fig.1a1a: Interaction between levels of shading (So to S4)and fruit types (primary (Fl ), secondary (F2 ) andtertiary (F)) on total soluble solids content ofthe fruit juice. Values are means of fruits from alltypes under each shading level. Trend analysis isprovided in Table 1~Iiio~7.8o::i07.6C/)W-J7.•lD:;:)<5 7 .2C/) LsDo.o~" 0.31-J 7L--=-:..:.-------'---------:~ F1 F2 F3~ FRUIT3 8oC/)W-JlD 6:;:)-JoC/) LSDo.o~" 0.65-J 4 L- --'-- -' -'- ---'~ 80 81 82 83 84~ SHADEo::i8gL-------:-:-~~~---1w-JlD7:;:)-JoC/) LSD 0.0.5 " 0.35~80LO---------O.L2----------.:0.~ D~FRUIT TYPE--- FRUIT 1 .. FRUIT 2 ...... FRUIT 3Fig.1cFig. 1c: Interaction between storage time (day 0 to day 4)and fruit types (primary (F) secondary (F) andtertiary (F) on total soluble solids content ofthe fruit juice. Values are means of fruits fromeach day of storage. Trend analysis is providedin Table 1Fig. 1b: Interaction between location of fruit (above' andbelouJ3) and fruit types (primary (Fl ), secondary(F) and tertiary (F])) on total soluble solidscontent of the fruit juice. Values are means offruit from all types in each location. Trend anay-lisis is provided in Table 1Fig.PERTANIKAJ. TRap. AGRIC. SCI. VOL. 17 NO.1, 1994 69AZIZAH B. OSMAN AND PETER B. DODDof unshaded fruits. The adverse effect of shadingon fruit size, carbohydrate content and dry mattercontent suggests that with crop density held at aconstant, the competition for resources amongfruits and between fruits and shoots results in alinear reduction of fruit size, internalcarbohydrate supply and dry matter content aslight exposure is reduced (Heinicke 1966; Jack-son and Palmer 1977; Jackson et at. 1977).However, in the present study fruit carbohydratecontent was not determined.All the quality attributes measured in thepresent study changed'significantly with storagetime (days), This was expected since the fruitsunder study were stored at ambient condition (20± 1°C, 70 ± 5% relative humidity), Our observa-tion showed that fruits from all treatments (dif-ferent levels of preharvest shading) were foundto be unacceptable due to excessive surface dehy-dration and loss of glossiness after day 4 (Osmanand Dodd 1994). These attributes were alsoobserved in fruits which were not subjected toany preharvest shading treatment. Therefore,shading does not extend the storage life of straw-berry fruit if it is just stored at ambient conditionafter harvest.REFERENCESDUEWER, RG. and C.C. ZYCH. 1967. Heritability ofsoluble solids and acids in progenies of the cul-tivated strawberry (Fragaria x ananassaDuch.).Proceedings Amer. Soc. Hort. Sci. 90: 153-157.HEINICKE, D.N. 1966. Characteristics ofMcIntosh andRed Delicious apples as influenced by expo-sure to sunlight during the growing season. JAmer. Soc. Hort. Sci. 89: 10-13.HUELIN, F.E. 1961. Chemical aspects of fruit quality.Fruit Preservation Quarterly 21: 12-14.JACKSON,J.E. andJ.W. PALMER. 1977. Effects of shadeon the growth and cropping of apple trees. II.Effects on components ofyield. J Hort. Sci. 52:253-266.JACKSON, J.E., PALMER, J.W., PERRING, M.A and RD.SHARPLES. 1977. Effects of shade on the growthand cropping ofapple trees. III. Effects on fruitgrowth, chemical composition and quality atharvest and after storage. J Hort. Sci. 52: 267-282.MA!uwas, P. andRJ. EMBs. 1964. Conversion ofsugarsto organic acids in the strawberry fruit. J FoodSci. 29: 629-630.MooRE,j.N. and W.A. SISTRUNK. 1980. Breeding straw-berries for superior fruit quality. In TheStrawberryed. N.F. Childers, p.149-155. Florida:Horticultural Publications.MORGAN, D.C., STANLEY, CJ., VOLZ, R. and IJ.WARRINGTON. 1984. Summer pruning of Galaapple: The relationships between pruning time,radiation penetration and fruit quality. J Amer.Soc. Hort. Sci. 109:637-642.OLSEN, KL. and G.e. MARTIN. 1980. Influence ofapplebloom date on maturity and storage quality ofStarking delicious apples. J Amer. Soc. Hart. Sci.105: 183-186.OSMAN, AB. and P.B. DODD. 1994. Effects ofdifferentlevels of preharvest shading on the storagequality of strawberry (Fragaria x ananassaDuchesne) cv. Ostara. I. Physical characteristics.PertanikaJ Trop. Agric Sci. 17(1): 55-64PArrEN, KD. and E.L. PROEBSTING. 1986. Effect ofdif-ferent artificial shading times and natural lightintensities on the quality of Bing sweet cherry.J Amer. Soc. Hart. Sci. 111: 360-363.ROBINSON, T.L., Ej. SEELEY, and B.N. BARRITT. 1983.Effect of light environment and spur age onDelicious apple fruit size and quality. J Amer.Soc. Hart. Sci. 108: 855-861.RYUGo, K and e. INTRIERI. 1972. Effect of light ongrowth of sweet cherry (Prunus avium L.) fruit.J Amer. Soc. Hort. Sci. 97: 691-694.SCOTT, D.H. and F.G.UWRENCE.1975. Strawberries. InAdvances in Fruit Breeding ed. J. Janick and J.N.Moore. p, 71-97. Lafayette, Indiana: PurdueUniversity Press.SEELEY, Ej., MICKE, W.e. and R KAMMERECK. 1980.Delicious apple fruit size and quality as influ-enced by radiant flux density in the immediategrowing environment. J Amer. Soc. Hart. Sci. 105:642-647.SHAW, DV, RS. BRINGHURST, and V VOTH. 1987. Geneticvariation for quality traits in an advanced-cyclebreeding population of strawberries. J Amer.Soc. Hart. Sci. 112: 699-702.SISTRUNK, W.A andJ.N. CAsH. 1973. Non-volatile acidsof strawberries. J Food Sci. 38: 807-809.70 PERTANlKAJ. TRap. AGRIC. SCI. VOL. 17 NO.1, 1994EFFECfS OF PREHARVEST SHADING ON STRAWBERRY - II. CHEMICAL CHARACfERISTICSSISTRUNK, WA. and J.N. MOORE. 1983. Quality. InMethods in Fruit Breeding ed. J.N. Moore and J.Janick. p 274-293. West Lafayette: Purdue Uni-versity Press.WENT, F.W.1957. The strawberry in the experimentalcontrol of plant growth. Chronica Botanica 17:129-138.WHITING, C.C. 1958. The non-volatile organic acids ofsome berry fruit. J Sci. Food andAgric. 9:244-248.(Received 23 May 1992)PERTANIKAJ. TRap. AGRIC. SCI. VOL. 17 NO.1, 1994 7]

Effects of different levels of preharvest shading on the storage quality of strawberry (Fragariax ananassaDuchesne) cv. Ostara II. chemical characteristics

The effects of shading developing fruits up to harvest on strawberry (Fragaria X ananassa Duchesne) cv. 'Ostara '

fruit quality were studied. Plants were shaded with netting of different levels of light penetration (74,58, 48,38 and

5% which are denoted by S(J SJ' S2' S3 and S4 respectively). Results showed that effects could only be detected when

plants were subjected to a very low level of light intensity, S4 . Location of fruits on the plant affected the fresh fruit

weight, surface glossiness and fruit firmness significantly. Fruits shaded by leaves were heavier and able to retain

surface glossiness longer than exposed fruits

Effects of sifferent levels of preharvest shading on the storage quality of strawberry (Fragariax ananassa Duchesne) cv. Ostara I. physical characteristics

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Effects of different levels of preharvest shading on the storage quality of strawberry (Fragariax ananassaDuchesne) cv. Ostara II. chemical characteristics

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