Fruit Quality Evaluation of Strawberry Cultivars Grown in Argentina

Fruit Quality Evaluation of Strawberry Cultivars Grown in Argentina A.K. Yommi, A.M. Borquez and S.L. Quipildor INTA, Estación Experimental Agropecuaria Famaillá, CC 11 (4132) Famailla Tucuman, Argentina

D.S. Kirschbaum Department of Pomology University of California One Shields Avenue, Davis CA 95616, USA

Keywords: Fragaria x ananassa, firmness, color, soluble solids content, vitamin C, acidity Abstract Fruit quality of different strawberry (Fragaria x ananassa) cultivars was evaluated in Tucuman (Argentina) from June to August (2001), a period when fruit prices are above the average values of the season. Cold-stored (frigo) plants (FGP) of 'Aromas', 'Camarosa', 'Gaviota' and 'Selva', and fresh plants (FHP) of 'Camarosa', 'Earlibrite', 'Gaviota', 'Rosa Linda', 'Sweet Charlie' and 'Tud New' were grown in a winter production system. Fruit were harvested periodically and samples of 15 fruit (>75% red color) per cultivar were analyzed during June and July (FGP) and August (FHP). Fruit quality was evaluated in terms of fruit weight, external and juice color (L*, °hue, chroma), firmness, soluble solids (SSC) and ascorbic acid contents, acidity and ratio (SSC/acidity). Within FGP, 'Camarosa' and 'Selva' had the highest external chroma values, while 'Gaviota' and 'Aromas' had intermediate and the lowest external chroma values, respectively. Levels of acidity were different within cultivars, with 'Camarosa' being the most acid of the group. Within FHP, 'Tud New' had high fruit weight, firmness, ascorbic acid content, and low °hue, which is desirable in terms of quality; however, L* (external and juice), SSC and ratio were low. ‘Camarosa’ had relatively high values of firmness, SSC and acidity, and was low in external and juice °hue. 'Earlibrite' had relatively high values of fruit weight, firmness, SSC, acidity and ascorbic acid. 'Sweet Charlie' had high SSC, intermediate firmness, and low acidity and ratio. Although production patterns of FGP and FHP were not the same and both groups were not fruiting simultaneously, 'Camarosa' and 'Gaviota', which were included in both groups, produced smaller fruit from FGP than from FHP, but firmness and SSC in FGP were the highest. These differences could be related to the particular background of each kind of plant and/or to environmental conditions during the fruiting season. INTRODUCTION Argentina, with 1,080 hectares and a production of 25,000 ton/year, is the second largest strawberry (Fragaria x ananassa) producer in South America, after Brazil. Strawberries are produced year-round, as they are planted across a broad range of latitude (24°S to 42°S), with climates ranging from cold-temperate to tropical (Kirschbaum and Hancock, 2000). Three major production regions - northern, central, and southern - can be distinguished, based on their particular climate and harvest season (Rodriguez and Hompanera, 1988). The northwestern province of Tucuman produces 30% of Argentina’s strawberries. Typically, the Argentine strawberry industry uses either fresh or cold-stored (‘frigo’; Voth, 1980) transplants. Fruit production is mostly concentrated in the spring, which is correlated with a marked decrease in fruit prices. Conversely, the highest fruit prices occur at the end of fall and in winter (May to August; Kirschbaum and Hancock, 2000). Tucuman takes advantage of its mild winter and top technology to harvest strawberries during the winter; however, increasing temperatures in September and decreasing fruit size result in deterioration of fruit quality. Fresh plants are currently used for the normal harvesting season which extends from June to November. Proc. XXVI IHC – Issues and Advances in Postharvest Hort. Ed. R.K. Prange Acta Hort. 628, ISHS 2003 Publication supported by Can. Int. Dev. Agency (CIDA)

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Frigo plants, when used in a winter/spring production system, have a brief production peak in June-July, no fruit in August and a major peak in September-October. The quality of fruit produced from frigo plants in September-October is comparable to that of the first fruit produced by fresh plants, which compensates the reduction in quality of fruit from fresh plants in spring. This allows growers to remain competitive throughout the season. Because of the reasons given above, frigo plants could be consider as a supplement to fresh plants both early and late in the season. Generally, fruit quality attributes for shippers and retailers are not fine-tuned to consumer preferences. Shippers and retailers demand size, color and firmness, while consumers demand flavor over any other quality factor. These characteristics are genotype-related; however, they are significantly affected by environment. Sims et al. (1997) found variations in external fruit color, soluble solids content and flavor among years and among different harvests within the same year. This study was designed to evaluate fruit quality of different cultivars and plant types (fresh and frigo) at different harvesting dates in winter. MATERIALS AND METHODS Fruit quality of different strawberry cultivars was evaluated from June to August. Cold-stored (frigo) plants of 'Aromas', 'Camarosa', 'Gaviota' and 'Selva', and fresh plants of 'Camarosa', 'Earlibrite', 'Gaviota', 'Rosa Linda', 'Sweet Charlie' and 'Tud New' were grown in a winter production system in 2001. The trials were conducted on a loamy soil at the INTA-Municipalidad de Lules Cooperative Research and Extension Center (CEAL), in Tucuman, Argentina. Frigo plants were set in the field on April 15 and fresh plants on May 7. Cropping beds consisted of mechanically-built raised beds 0.40 m high, 0.50 m wide, and 1.25 m between centers. Plant spacing within each two-row bed was 0.30 m. Row spacing within the bed was 0.30 m. Drip irrigation tubes were laid on the beds, which were covered with black polyethylene mulch. The standard fertilization program for Lules was used (INTA, 2000). In order to protect flowers from frost damage, plants were covered with clear polyethylene (50 µm thick) one-row tunnels from May to August. Fruit with more than 75% red color was harvested once a week during June and July (cold stored plants) and August (fresh plants). Four samples of 15 fruit (from four different blocks) of each cultivar were evaluated for fruit weight, external and juice color (L*=brightness, °hue=tone, chroma=intensity), firmness, soluble solids content (SSC), acidity, ratio (SSC/acidity) and ascorbic acid content. As fruit production from frigo plants was scarce, each harvesting date was considered as a block. Fruit were individually weighed. External color was determined on both sides of the fruit (Sacks and Shaw, 1994) with a MINOLTA Chromometer CR300, using L*a*b* color space. Firmness was measured on two replicates of each fruit with an Effegi penetrometer, with a 3 mm diameter plunger tip. Juice was extracted for determination of color (L*, °hue and chroma), soluble solids content (SSC, determined with an Atago refractometer), titratable acidity as citric acid content (by titration of 10 g of juice diluted in 100 ml of distilled water, using NaOH to ph 8.1), ratio (SSC/titratable acidity) and ascorbic acid or vitamin C (as mg of ascorbic acid/100 g of juice) by titration of 10 g of juice dissolved in 100 ml of distilled water, using 0.02 mol·L-1 KI and starch solution as color indicator. Data were subjected to analysis of variance at P=0.05 and mean separation performed by LSD test with SAS 8.01. RESULTS AND DISCUSSION Frigo Plants Fruit surface color intensity and acidity were significantly different among cultivars (Table 1). ‘Camarosa’ and ‘Selva’ had the highest external color intensity. 872

‘Camarosa’ had the highest index of acidity. There were no significant differences among cultivars in terms of fruit size (weight), external color brightness and tone, firmness, soluble solids content (SSC), ratio (SSC/acidity), ascorbic acid and juice color (intensity, brightness and tone). The values of SSC for ‘Aromas’, ‘Camarosa’ and ‘Gaviota’ were higher than those reported by D’Anna and Prinzivalli (2002); however, the ranking of firmness for these three cultivars was identical in both studies. Fresh Plants The interaction between cultivar and sampling date was significant for fruit weight, firmness, external color brightness, juice color tone and ascorbic acid content (Table 2). ‘Earlibrite’ had the highest fruit weight in three out of four sampling dates, which agrees with Chandler (1997), who found similar results when ‘Camarosa’, ‘Earlibrite’ and ‘Sweet Charlie’ were compared. Regarding external color, ‘Sweet Charlie’ and 'Tud New' showed the lowest and the highest brightness, respectively (Table 2). The external color tone of 'Tud New' was lower than the external color tone of ‘Camarosa’, regardless of the sampling date (Table 3). The ranking of external color intensity was (in decreasing order) as follows: ‘Sweet Charlie’, 'Rosa Linda’, 'Camarosa', and 'Tud New' (Table 3). Firmness of the fruit from ‘Tud New’, ‘Earlibrite’ and 'Camarosa' was among the highest in three out of the four sampling dates (Table 2). When juice was analyzed, except for the first harvest date, there were significant differences in brightness among cultivars, with 'Tud New' being the darkest. Regarding hue angle, differences were found in the second week of August, when 'Tud New' and 'Camarosa' were closer to purple-red than the other cultivars. 'Tud New' had the lowest juice color intensity (Table 2). SSC, acidity, and ratio were significantly different among cultivars and harvesting dates. 'Sweet Charlie' and 'Earlibrite' showed the highest SSC followed by ‘Camarosa’. This is in agreement with D’Anna and Prinzivalli (2002), who showed similar values for ‘Sweet Charlie’, ‘Camarosa’, ‘Tud New’ and ‘Rosa Linda’ (‘Earlibrite’ was not included in this study). 'Gaviota' and 'Tud New' had the lowest SSC. 'Gaviota' and 'Sweet Charlie' had relatively reduced acidity and 'Camarosa' was the most acidic. Ruiz-Nieto et al. (1997) reported that 'Camarosa' had high acidity, especially when compared with 'Sweet Charlie'. 'Sweet Charlie' and ‘Earlibrite’ SSC/acidity ratios were the highest with ´Tud New´ having the lowest ratio (Table 3). ‘Earlibrite’ was among the cultivars with the highest levels of ascorbic acid in the entire period. External color, juice color, SSC, acidity and ratio were affected by sampling date (Table 3). Differences could be related to the fact that the maturity stage of the samples at each date was not identical, even though criteria for choosing fruit to be harvested were the same. Moreover, samples from Aug 15 always showed the highest or lowest values for the variables cited above. The only significant environmental condition that could be related to this event was the presence of fog the day before sampling and a fully clouded sky on the sampling date. This may explain why the lowest SSC level was found on Aug 15. Sims et al. (1997) reported that SSC can vary among harvesting dates and years of evaluation. Chandler (1997) showed that sweetness and firmness may vary between two consecutive years. This agrees with Shaw et al. (1987), who showed how environment could affect SSC, and with Went (1957, cited by Darrow, 1966), who correlated sugar content to light intensity. Fruit load was discarded as a possible factor affecting SSC since there was no correlation between fruit load and SSC for the same cultivar (Table 4). Lack of sun did not affect ascorbic acid content, although Darrow (1966) suggested that berries on the plant ripening in the sun have increased ascorbic acid content over those ripening in the shade. The effect of cultivar on fruit quality was also reported for various cultivars, although growing conditions and methodology of these studies were different (Cordenunsi et al., 2002; Ruiz-Nieto et al., 1997). 873

Although production patterns of cold-stored and fresh plants were not the same and both groups were not fruiting simultaneously, 'Camarosa' and 'Gaviota', which were included in both groups, produced smaller fruit from cold-stored than from fresh plants, but firmness and SSC were higher in frigo than in fresh plants. Thus, 'Camarosa' consistently showed the highest acidity regardless of plant type. The differences in terms of quality for the same cultivar but between plant types could be related to the particular background of each kind of plant and/or to the environmental conditions during the sampling seasons. The genotype has a major effect on fruit quality (Cordenunsi et al., 2002). Future studies should examine how the environment affects fruit quality so as to understand how fruit quality is controlled during fruit development. ACKNOWLEDGEMENTS We thank G. Fragaris and strawberry growers from Tucuman for providing the plants for the trials. Literature Cited Chandler, C.K. 1997. ‘Sweet Charlie’ strawberry. HortScience 32:1132-1133. Cordenunsi, B.R., Oliveira do Nascimento, J.R., Genoves, M.I. and Lajolo, F.M. 2002. Influence of cultivar on quality parameters and chemical composition of strawberry fruits grown in Brazil. J. Agri. Food Chem. 50:2581-2586. D'Anna, F. and Prinzivalli, C. 2002. Due anni di studio su varieta di fragola per l'ambiente protetto meridionale. Frutticoltura LXIV(6):61-68. Darrow, G. M. 1966. The strawberry: history, breeding, and physiology. 1st ed. Holt, Rinehart and Winston, New York. INTA Famaillá. 2000. Frutilla. Strawberry web site of Estación Experimental Agropecuaria INTA Famaillá (Argentina). http://www.inta.gov.ar/famailla/frutilla Kirschbaum, D.S. and Hancock, J.F. 2000. The strawberry industry in South America. HortScience 35:807-811. Rodriguez, J.P. and Hompanera, N. 1988. Produccion de Plantines para la Multiplicacion de Frutilla. Manual de Produccion de Semillas Horticolas. Fasciculo II. Instituto Nacional de Tecnología Agropecuaria -Mendoza, Argentina. Ruiz-Nieto, A., Lopez-Aranda, J.M., Lopez-Montero, R., Lopez-Medina, J. and Medina, J.J. 1997. Analysis of sugars from strawberry cultivars of commercial interest contents evolution. Acta Hort. 439:663-667. Sacks, E.J. and Shaw, D.V. 1994. Optimum allocation of objective color measurements for evaluating fresh strawberries. J. Amer. Soc. Hort. Sci. 119:330-334. Shaw, D.V., Bringhurst, R.S. and Voth, V. 1987. Genetic variation for quality traits in an advanced-cycle breeding population of strawberries. J. Amer. Soc. Hort. Sci. 112:699702. Sims, C.A., Chandler, C.K., Eastridge, J.S. and Golaszewski, R.R. 1997. Seasonal changes in fruit quality of several strawberry genotypes grown in Florida. Adv. Strawb. Res. 16:48-56. Voth, V. 1980. California cultural systems. p. 67-76. In: N.F. Childers (ed.), The Strawberry. Horticultural Publ., Gainesville, Florida.

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Tables Table 1. Frigo plants: Fruit size (weight), external color and juice color, firmness, soluble solids content (SSC), acidity, ratio* and ascorbic acid content of different cultivars. Cultivar Aromas Camarosa Gaviota Selva

Fruit weight (g) 11.65 9.25 9.86 9.71 NS

LSD 1

External color L* °hue Chroma 36.79 33.44 33.82 39.14 33.56 40.59 40.19 35.17 35.74 42.11 37.70 40.36 NS NS * 5.39

L* 49.30 53.56 48.00 62.36 NS

Juice color Firmness (N) °hue Chroma 46.42 48.23 6.38 50.70 52.88 6.32 46.23 50.81 5.25 37.91 46.94 5.93 NS NS NS

SSC (%) 7.9 9.4 8.9 8.6 NS

Acidity

Ratio1

0.69 0.94 0.65 0.75 * 0.15

11.55 10.39 13.40 11.80 NS

Ascorbic acid 68.40 83.87 83.25 67.05 NS

Ratio SSC/acidity.

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Table 2. Harvesting date x cultivar effects on external color, juice color, firmness, soluble solids content (SSC), acidity and ascorbic acid. Harvest Date 7/8

Cultivar

Fruit Ext. Color size L* (g) Camarosa 13.8 35.2 Earlibrite 12.9 35.2 Gaviota 12.9 35.7 Rosa Linda 12.9 38.7 Sweet Charlie 12.7 39.2 Tud New 15.9 33.9 LSD 2.1 2.8

Juice color L* °hue

Firmness SSC Acidity Ascorbic Acid (N) (%)

31.93 36.09 37.56 42.38 33.50 37.89 NS

48.47 48.99 47.12 45.16 49.57 42.99 NS

3.42 4.47 2.97 2.78 4.35 4.22 0.79

7.7 8.4 7.1 7.1 8.4 7.3 0.8

0.85 0.70 0.65 0.68 0.64 0.80 0.06

84.0 96.0 81.9 88.8 87.0 97.2 9.8

15/8 Camarosa Earlibrite Gaviota Rosa Linda Sweet Charlie Tud New LSD

14.7 18.0 15.2 14.7 13.7 17.0 NS

37.2 39.3 37.8 38.8 42.4 33.9 1.5

47.44 49.92 42.42 47.74 51.95 32.25 11.76

43.57 44.20 43.74 44.86 43.39 43.29 NS

4.52 3.40 4.64 3.77 2.73 5.52 NS

7.4 8.3 6.2 6.5 7.9 6.3 0.8

0.90 0.75 0.66 0.66 0.71 0.80 0.07

76.8 93.6 78.3 79.6 84.6 94.5 11.0


19.7 22.1 16.1 14.8 20.8 17.6 4.0

37.0 40.7 38.3 39.9 41.3 34.6 1.8

52.13 46.68 45.17 45.42 50.36 32.71 9.28

41.66 45.02 43.94 43.81 42.73 41.55 1.52

4.68 4.39 3.52 3.30 3.86 4.66 0.36

8.1 8.7 7.0 7.6 8.9 7.2 0.9

0.87 0.70 0.64 0.69 0.59 0.78 0.05

104.4 105.6 97.6 94.0 100.8 90.0 NS


20.0 22.4 17.2 15.7 20.8 19.2 3.7

36.2 39.4 37.3 39.2 39.6 35.5 1.2

51.19 51.91 48.15 48.06 51.14 36.62 6.48

41.87 45.20 44.41 44.57 44.79 41.77 2.35

4.05 3.85 3.15 3.05 3.23 4.38 0.39

7.3 7.9 6.6 7.4 8.4 6.8 0.8

0.91 0.72 0.63 0.70 0.65 0.77 0.11

70.8 89.1 85.8 73.8 67.5 70.8 7.1

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Table 3. Independent effects of cultivar and harvesting dates on external color, juice color, soluble solids content (SSC), acidity and ratio. Cultivar Camarosa Earlibrite Gaviota Rosa Linda Sweet Charlie Tud New LSD

External color °hue Chroma 31.28 37.07 32.97 36.45 32.59 36.79 32.76 41.36 33.13 42.95 28.27 36.18 1.17 0.87

Juice color Chroma 51.01 54.54 48.75 55.34 51.79 42.35 5.04

SSC

Acidity

Ratio1

7.62 8.32 6.71 7.19 8.45 6.90 0.38

0.88 0.71 0.64 0.69 0.64 0.79 0.04

8.66 11.73 10.41 10.50 13.21 8.78 0.78

55.93 46.74 49.39 51.31 4.11

7.69 6.89 7.86 7.45 0.31

0.73 0.74 0.71 0.73 0.03

10.7 9.4 11.2 10.4 0.6

Harvest date 7/8 15/8 24/8 29/8 LSD 1

31.02 33.41 30.57 32.10 0.95

35.23 42.06 38.09 38.11 0.71

Ratio is SSC/acidity

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Table 4. Harvest date x cultivar effects on fruit number and weight per plant. Harvest date

Cultivar Camarosa Earlibrite Gaviota Rosa Linda Sweet Charlie Tud New

Number of fruit /plant 0.65 0.43 0.31 0.78 0.46 0.63

Fruit weight (g)/plant 8.86 6.09 3.97 9.97 5.98 10.02

7/8

15/8

Camarosa Earlibrite Gaviota Rosa Linda Sweet Charlie Tud New

0.73 0.53 0.70 1.48 0.50 0.83

10.02 10.52 10.92 24.17 7.25 14.30

24/8


0.68 0.68 0.78 1.81 0.91 0.90

12.85 14.19 11.45 26.97 16.06 15.27

29/8


0.79 0.77 0.63 1.37 0.76 0.78

15.44 18.58 11.75 21.98 16.26 14.74

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