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Effect of harvest season, maturity and storage temperature on storability of carambola ‘Honglong’ fruit
Scientia Horticulturae 220 (2017) 42–51
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Effect of harvest season, maturity and storage temperature on storability of carambola ‘Honglong’ fruit Shao-Wei Chen a , Min-Chi Hsu b , Hsin-Hsiu Fang c , Shang-Han Tsai a , Yu-Shen Liang a,∗ a
Department of Plant Industry, National Pingtung University of Science and Technology, No.1, Shuefu Rd., Neipu, Pingtung 91201, Taiwan, ROC Crop Science Division, Taiwan Agricultural Research Institute, No.189, Zhongzheng Rd., Wufeng Dist., Taichung City 41362, Taiwan, ROC Department of Tropical Fruit Tree, Fengshan Tropical Horticultural Experiment Branch, Taiwan Agricultural Research Institute, No. 530, Wenlong E. Rd., Fengshan Dist., Kaohsiung City 830, Taiwan, ROC b c
a r t i c l e
i n f o
Article history: Received 18 January 2017 Received in revised form 22 March 2017 Accepted 24 March 2017 Available online 31 March 2017 Keywords: Chilling injury Titratable acidity Total soluble solids Storage life Shelf life
a b s t r a c t Averrhoa carambola L. cv. Honglong is a species newly bred in Taiwan for commercial purposes. However, few studies have been conducted on the storage and transportation of this fruit. Accordingly, the present study investigated the influences of harvest reasons, fruit maturity, and storage temperature on the food quality and storage life of ‘Honglong’ fruits. The results showed that the color and firmness of summer fruits were superior to those of winter fruits; the winter fruits at 70% or 80% maturity had a significantly longer the storage life than the corresponding summer fruits. Fruits with 70% maturity (i.e., when half of the fruit is yellow) are bright green-yellow, high in total soluble solids (7.1◦ Brix for winter fruits and 7.5◦ Brix for summer fruits), and low in titratable acidity (0.34% for winter fruits and 0.32% for summer fruits). In addition, the storage life and cold resistance of fruits with 70% maturity had a longer life and were more resistant to cold than those with 60% maturity were. The transportation storage temperature of 5 ◦ C caused slight chilling injury but was optimal for maintaining food quality, storage life, and shelf life. Storage temperatures of 0 and 3 ◦ C caused severe chilling injury, and 10 ◦ C caused the fruits to rapidly turn yellow and rot. We suggest that ‘Honglong’ fruits be harvested at 70% maturity and be stored at 5 ◦ C to achieve optimal quality for commercial production. © 2017 Elsevier B.V. All rights reserved.
1. Introduction Averrhoa carambola L. cv. Honglong is a member of the Oxalidaceae family. Carambola fruit is oval or elliptical with three to five longitudinal ribs. The fruit derives its vernacular name “starfruit” from its star-shaped cross section; it was a potent natural antioxidant food and contained abound in phenolic compounds (Tongchitpakdee, 2012; Yan et al., 2013). Carambola fruit has a sour tart or mildly sweet taste depending on the species and level of maturity. The fruit can be eaten fresh or after processing (Morton, 1987; Wu et al., 2004). Prior to 2010, the main cultivars of carambola fruits exported from Taiwan was Averrhoa carambola L. cv. Chang Tsey (‘Chang Tsey’ carambola), accounting for 40% of carambola fruit exports. In recent years, ‘Chang Tsey’ carambola crops were often damaged by pests and disease, and the frequent use of pesticide increased production costs. Accordingly, the agricultural area for cultivating
∗ Corresponding author. E-mail addresses: [email protected] (S.-W. Chen), [email protected] (M.-C. Hsu), [email protected] (H.-H. Fang), [email protected] (S.-H. Tsai), [email protected] (Y.-S. Liang). http://dx.doi.org/10.1016/j.scienta.2017.03.047 0304-4238/© 2017 Elsevier B.V. All rights reserved.
‘Chang Tsey’ carambola gradually reduced, and another species, ‘Honglong,’ became dominant for cultivation. Fengshan Tropical Horticultural Experiment Branch first cultivated ‘Honglong’ with self-seedlings obtained from the species ‘Jakarta.’ The peel of the fruit is orange-red and has thick, firm ribs; it is considered delicious, suitable for storage and transportation, and is therefore preferred by for export. Currently, ‘Honglong’ carambola is the main species exported from Taiwan (Liu, 2009). When managed properly, carambola fruits can be harvested three times annually (Wu et al., 1993). In Florida, carambola fruits are harvested from June to February; however, the main harvest periods are August–October and December–February. In Malaysia, the fruit is harvested throughout most of the year; however, the main harvest periods are April–May, July–August, and November–December (Tongchitpakdee, 2012). In Taiwan, except for the low harvest from May to July, most harvests during other periods are exported. Product quality and nutritional quality are influenced by the climate. For example, lettuce is typically grown at low temperatures and has a firm head with a mild flavor. If lettuce is grown at high temperatures or during droughts, its leaves will be less tender even if the flavor quality of the head excellent (Peirce, 1987).
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Harvest maturity is crucial for quality management and has a marked influence on product quality (Braman et al., 2015). It can also influence the metabolic responses of vegetables and fruits. Therefore, it is a crucial factor that determines product quality, storage potential, and storage disorder (O’Hare, 1993; Siddiqui and Dhua, 2010). Currently, to prevent mechanical damage to carambola fruits during long-distance transportation and after-harvest handling, exporters suggest that the fruit should be harvested at the color-break stage (O’Hare, 1993). Because total soluble solids (TSS) content in carambola fruits increases with maturity, Warren et al. (2007) suggested that the fruit of Averrhoa carambola L. cv. Arkin (‘Arkin’ carambola) should be harvested after the color-break stage to ensure excellent food quality. Cold storage is commonly used to transport fruits to international markets, however, tropical fruits are susceptible to chilling injury (Mustafa et al., 2016). The influence of storage temperature on the quality of fruits and vegetables depends on the metabolic rates of them. Dodd and Bouwer (2014) suggested that the optimum temperature and relative humidity for storage of carambola fruits were 7–10 ◦ C and 85–95%, respectively. Under these conditions, the storage life of the fruits is approximately 21–35 days. Cantwell (2002), however, suggested that the optimum storage temperature and relative humidity were 9–10 ◦ C and 85% to 90%, respectively. Under these conditions, the storage life of the fruit is approximately 3–4 weeks. Numerous reports have indicated that for this fruit, storage temperature ≤5 ◦ C causes chilling injury (CI), which becomes severe with longer storage times (Miller and McDonald, 1997; Wan and Lam, 1984; Warren et al., 2007). ‘Honglong’ is a newly bred species that has been widely accepted by farmers and consumers in Taiwan. Furthermore, it has become a major carambola cultivar. However, few studies have examined the physical, storage, and transportation characteristics of this cultivar to derive a reference for business operators regarding the optimum storage and transportation conditions. Accordingly, in the present study, the influences of the harvest season, fruit maturity, and storage temperature on the fruit quality and storage life of ‘Honglong’ were investigated.
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CI index were investigated. At 7, 14, 21, 28, 35, and 42 days, fruits were stored at 25 ◦ C to investigate their shelf life. Each analysis was carried out 5 replications and each replication included two fruit samples. 2.2. Experiment II. Storage temperature During winter (February 4th) and summer (August 27th) in 2013, fruits having 70% maturity were harvested and sent to the laboratory. The 70% maturity of carambola is mainly harvest maturity for commercial exportation in Taiwan. Fruits were removed if they were over- or under-ripened or affected by pests, disease, or mechanical damage. The remaining fruits were stored in a refrigerator at 0, 3, 5, or 10 ◦ C and their storage life, chilling injuring index, and quality investigated. After 7, 14, 21, 28, 35, and 42 days of storage, the fruits were then stored at 25 ◦ C and their shelf life was investigated. Each analysis was carried out 5 replications and each replication included two fruit samples. 2.3. Quality characteristics 2.3.1. Color The color of the rib peel was determined at three points (top, middle, bottom) and a mean value was calculated for each piece of fruit. A color difference meter (ZE-2000, Nippon Denshoku) was used to measure the lightness and to obtain the values of a and b. The lightness values ranged from 0 to 100, with lower values representing darker colors. Hue value ( value = tan−1 |b/a|) was used to represent the color change in the fruit (0◦ = red-purple, 90◦ = yellow, 180◦ = blue-green, and 270◦ = blue). Color intensity was represented by C = [(a2 + b2 )1/2 ], with higher values indicating higher color intensity (McGuire, 1992). 2.3.2. Firmness A property analyzer EZ-test 500N, Shimadzu with a No. 5 probe (diameter, 5 mm) was employed to measure the fruit firmness. The probe depth was set to 10 mm. Measurements (N) were performed at the top, middle, and bottom parts of the ribs, and a mean value was calculated for each piece of fruit.
2. Materials and methods 2.1. Experiment I. Harvest maturity ‘Honglong’ fruits were harvested in Ligang Township (Pingtung County, Taiwan) during winter (February 26th) and summer (September 10th) in 2012. Fruit maturity was determined through visual inspection, and three levels of maturity were determined: 60% maturity (one-quarter of the fruit had turned yellow), 70% maturity (half of the fruit had turned yellow), and 80% maturity (three-quarters of the fruit had turned yellow). The inspection criteria are defined as follows: 60% maturity: the fruit is not fully developed, the outer edge of its ribs appear dark green, and the ribs appear light green (approximately 65–75 days after blossoming for summer fruits and approximately 100–110 days after blossoming for winter fruits); 70% maturity: the fruit is fully developed, the outer edge of its ribs appear light green, and approximately half of its ribs are yellow (approximately 70–80 days after blossoming for summer fruits and approximately 105–115 days after blossoming for winter fruits); and 80% maturity: the color of a fruit has begun changing, but the outer edge of its ribs remain green (approximately 80–90 days after blossoming for summer fruits and approximately 115–125 days after blossoming for winter fruits). The fruits were selected and sent to a laboratory. Fruits were removed if they were over- or under-ripened or affected by pests, disease, or mechanical damage. The remaining fruits were stored in a refrigerator at 5 ◦ C and their storage life, quality, and
2.3.3. Total soluble solid The TSS content in the juice was measured using a hand-hold refractometer N-IE, Atago; the TSS value was presented in ◦ Brix. The TSS of the top, middle, bottom parts of the ribs of each fruit were measured and the mean TSS value was calculated for each fruit. 2.3.4. Titratable acidity Carambola pulp of 10 g was added to 100 mL of distilled water; the mixture liquid was filtered by using filter paper (Whatman No. 1). Subsequently, 25 mL of filtrate was removed and titrated in 0.1 M NaOH. An automatic potentiometric titrator (DL53, Mettler Toledo) was employed to titrate the filtrate until its pH was 8.1. The NaOH titration of the sample was converted into the chemical equivalent of citric acid to obtain the total titratable acidity (TA) (%) of the sample (Teixeira et al., 2008; Ashok et al., 2011). 2.4. Chilling injury Chilling injury (e.g., black or brown depressed spots) due to low temperature was assessed through visual observation. Three CI index were determined (index 0–2). The criteria were defined as follows: CI index 0: the peel is bright and without CI; index 1: the peel exhibits slight CI with brown depressed spots covering less than 20% of the peel; and index 2: the peel shows clear CI with brown depressed spots covering more than 20% of the peel. The CI
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Fig. 1. The lightness, chroma and hue value of ‘Honglong’ fruits (A, C, E for winter fruit and B, D, F for summer fruit) with different maturity that stored at 5 ◦ C condition. The hairline in each storage day was LSD value at p < 0.05.
index was calculated, according to the severity of symptoms and the number of fruit. Fruit with CI index 2 has no commercial value. 2.5. Storage life For each experiment, if half of the fruits stored at low temperature had disease or mildew, had turned completely yellow (90% maturity), exhibited CI index 2, or appeared rotten, the storage life of repetition was concluded because the fruit would not appeal to consumers. Four replicates were conducted for storage life assay, and five fruits were used for each of four replicates. Each treatment was 20 fruits (4 replicates x 5 fruits) totally in each assay. 2.6. Shelf life Some fruits originally stored at low temperature were removed every second week and placed on a shelf at 25 ◦ C. In each experi-
ment, if half of the fruits had disease or mildew, turned completely yellow (90% maturity), exhibited CI index 2, or appeared rotten, the shelf life of repetition was concluded because the fruit would be accepted by the consumers. Three replicates were conducted for shelf life assay, and five fruits were used for each of four replicates. Each treatment was 15 fruits (3 replicates x 5 fruits) totally in each assay.
2.7. Statistical analysis Analysis of variance (ANOVA) was performed on the test data by using the statistical analysis system (SAS), with a least significant difference test at a 5% significance level. Chart plotting was performed using Sigma Plot 10.0 and Microsoft Excel.
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Fig. 2. The firmness, total soluble solids and titrable acidity of ‘Honglong’ fruits (A, C, E for winter fruit and B, D, F for summer fruit) with different maturity that stored at 5 ◦ C condition. The hairline in each storage day was LSD value at p < 0.05.
3. Results 3.1. Experiment I. Harvest maturity The quality characteristics of winter fruits (harvest: February 26th, 2012) and summer fruits (harvest: September 10th, 2012) at 60%, 70%, and 80% maturity were compared at harvest time (Table 1). The color of the fruits at the three maturity levels was compared; the hue value was found to gradually reduce with the maturity. Fruit quality was optimal at 60% maturity, becoming lower as the fruit matured. For both winter and summer fruits, the TSS at 80% maturity (winter: 7.9◦ Brix, summer: 10.3◦ Brix) was significantly higher than that at 60% maturity (winter: 6.9◦ Brix, summer: 7.0◦ Brix) and 70% maturity (winter: 7.1◦ Brix, summer:
7.5◦ Brix). The TA was the highest at 60% and 70% maturity for winter and at 60% maturity level for summer product reducing gradually as the fruit matured. The color of the fruits differed significantly between seasons (Table 1). The summer fruits were significantly brighter and more intense in color at all three maturity levels, whereas the hue value of the winter fruits was higher. In addition, the summer fruits were significantly firmer at all three maturity levels. TSS of 60% and TA of 60% and 80% maturity were significant difference between seasons; however, these results were not consistent across the three maturity levels. For all three maturity levels, we investigated the color and quality of fruits stored at 5 ◦ C. Initially, the lightness gradually decreased and then increased (Fig. 1A and B), whereas the chroma increased
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Table 1 The quality of ‘Honglong’ fruit with different maturities at harvest time. Season
Winter
LSD value Summer
Maturity
60% 70% 80% 60% 70% 80%
LSD value LSD value for 60% LSD value for 70% LSD value for 80%
Coloration
Lightness (L value)
Chroma (C value)
Hue value (degree sign)
23.5 ± 2.5ab B 21.4 ± 3.1bB 25.7 ± 2.4aB 2.857 38.1 ± 1.8aA 32.8 ± 2.2bA 34.2 ± 1.5bA 2.082 2.573 2.972 2.183
8.1 ± 1.2aB 7.7 ± 0.8aB 8.0 ± 1.1aB 1.235 12.6 ± 1.2bA 10.7 ± 1.6cA 15.1 ± 0.7aA 1.203 1.348 1.388 0.928
118.5 ± 6.5aA 115.0 ± 5.9aA 100.8 ± 8.6bA 7.840 112.9 ± 3.3aB 116.0 ± 3.9aA 92.2 ± 6.2bB 5.299 5.931 5.988 8.122
z
y
Firmness (N)
Total soluble solids (◦ Brix)
Titratable acidity (%)
13.8 ± 1.1aB 12.2 ± 1.1bB 11.0 ± 1.1cB 1.224 18.5 ± 1.0aA 14.4 ± 1.3bA 12.6 ± 1.4cA 0.823 1.588 1.412 1.549
6.9 ± 0.1bA 7.1 ± 0.3bA 7.9 ± 0.2aB 0.605 7.0 ± 0.2bA 7.5 ± 0.2bA 10.3 ± 0.3aA 0.646 0.454 0.613 0.807
0.31 ± 0.06aB 0.34 ± 0.16aA 0.27 ± 0.05bA 0.039 0.44 ± 0.25aA 0.32 ± 0.09bA 0.17 ± 0.08cB 0.068 0.061 0.060 0.049
z Each value is presented as the mean of four replicates. The means in same season with the same lowercase letter did not differ significantly at p < 0.05 using least significant difference test. y The means in same maturity between winter and summer with the same capital letter did not differ significantly at p < 0.05 using least significant difference test.
with time (Fig. 1C and D). At all three maturity levels, the hue value of the winter fruits gradually reduced after the fruits were stored at 5 ◦ C for 28 days; the hue value of summer fruits at 60% or 70% maturity rapidly decreased after 14 days of storage at 5 ◦ C; the hue value of summer fruits at 80% maturity did not change significantly during storage (Fig. 1E and F). During storage, the fruit gradually became softer with time (Fig. 2A and B). For both the winter and summer fruits, the TSS at 80% maturity was significantly higher than that at 60% or 70% maturity (Fig. 2C and D). The TSS in the summer fruits at 80% maturity increased during the late storage period (Days 35 and 42). The TA of the winter fruits gradually reduced during the late storage period, there were no significantly different at three maturity during storage; at 60% maturity, the TA of summer fruits also reduced during storage period, but that at 70% or 80% maturity did not change significantly (Fig. 2E and F). The TA of the winter fruits became lower during the late storage period; at 70% or 80% maturity, the TA of the summer fruits gradually became lower, but that at 60% maturity did not change significantly (Fig. 2E and F). The fruit of three maturity were stored at 5 ◦ C was investigated for CI during storage.Winter fruits exhibited CI after 12 days of storage at 5 ◦ C; the fastest increase in the CI index was observed in the winter fruits at 60% maturity, the CI index arrived 2 after 36 days of storage (Fig. 3). The CI indices of fruits at 70% and 80% maturity were respectively 1.8 and 1.6 after 42 days of storage. CI to the summer fruits became delayed as their maturity increased; fruits at 60%, 70%, and 80% maturity exhibited CI after storage for 14, 20, and 24 days, respectively. Compared with the winter fruits, the summer fruits exhibited less severe CI. We investigated the storage life and shelf life of the fruits at all three maturity levels. The storage life of the winter fruits at 70% or 80% maturity was significantly longer than that of the winter fruits at 60% maturity (Table 2). The storage life of summer fruit at different maturity stages was not significantly different. The winter fruits at 70% or 80% maturity had a significantly longer the storage life than the corresponding summer fruits; however, there was no difference in storage life between the winter and summer fruits at 60% maturity. To investigate the shelf life, some fruits were removed from lowtemperature storage each week and kept at 25 ◦ C. The shelf life was found to gradually become shorter with the storage time (Table 2). At all three maturity levels, fruits stored for 35 days at 5 ◦ C had a shelf life of approximately 3–5 days. No significant difference in shelf life was observed between the three maturity levels in 35th day of storage. The most limiting factor was rotting in shelf life experiments; after 21 days storage at 5 ◦ C, the fruit easily became rotten or grew mildew when stored at 25 ◦ C.
Fig. 3. The CI index of ‘Honglong’ fruits (winter and summer fruit) with different maturity that stored at 5 ◦ C condition. Each value is presented as the mean of four replicates.
3.2. Experiment II. Storage temperature We investigated the quality and storage characteristics of winter (harvest: February 4th, 2013) and summer (harvest: August 27th, 2013) fruits were stored at 0, 3, 5, and 10 ◦ C. The lightness of the winter fruits increased on 35 and 42 days of storage. The summer fruits became their brightest on 28 days of storage at 5 and 10 ◦ C; their peel brightness rapid reduced because of CI at these storage temperatures (Fig. 4A and B). The winter fruits gradually became more intense in chroma after 35 and 42 days storage at 5, and 10 ◦ C.
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Table 2 The storage life and shelf life of ‘Honglong’ fruit with different maturities that were harvested in winter and summer. Season
Maturity
Storage life (day)
Winter
60% 70% 80%
36.6 ± 0.2bz Ay 42.8 ± 0.4aA 42.6 ± 0.4aA 1.067 34.6 ± 1.8aA 37.2 ± 1.2aB 38.4 ± 1.0aB 4.269
LSD value Summer
LSD value
60% 70% 80%
Shelf life (day) 7D
14D
21D
28D
35D
42D
9.6 ± 1.9a 10.8 ± 0.5a 12.0 ± 0.0a 3.513 9.4 ± 0.2b 10.6 ± 1.3a 13.8 ± 0.7a 2.674
9.2 ± 0.7a 6.4 ± 0.6b 6.4 ± 0.6b 1.996 9.2 ± 0.7a 9.8 ± 0.6a 9.6 ± 1.1a 2.602
4.0 ± 0.0b 7.8 ± 0.5a 7.4 ± 0.4a 1.125 6.4 ± 0.7b 6.0 ± 0.6a 9.6 ± 0.6a 1.882
5.8 ± 0.7a 4.0 ± 0.0b 6.4 ± 0.6a 1.687 5.8 ± 0.4b 5.8 ± 0.2b 7.6 ± 0.6a 1.307
3.2 ± 0.5a 4.6 ± 0.6a 3.6 ± 0.4a 1.550 5.4 ± 0.2a 5.2 ± 0.2a 4.8 ± 0.6a 1.180
x 3.0 ± 0.0b 3.8 ± 0.2a 0.3558 3.0 ± 0.0a 2.6 ± 0.2a 2.2 ± 0.6a 1.125
x, It means the fruits was decay during storage. z Each value is presented as the mean. The means in same season with the same lowercase letter did not differ significantly at p < 0.05 using least significant difference test. y The means of storage life in same maturity between winter and summer with the same capital letter did not differ significantly at p < 0.05 using least significant difference test. The LSD value for 60% maturity between winter and summer was 4.264, for 70% maturity between winter and summer was 2.898, and for 80% maturity between winter and summer was 2.440.
Fig. 4. The lightness, chroma and hue value of ‘Honglong’ fruit (A, C, E for winter fruit and B, D, F for summer fruit) that stored in different temperature condition (0, 3, 5, 10 ◦ C). The hairline in each storage day was LSD value at p < 0.05.
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Fig. 5. The firmness, total soluble solids and titrable acidity of ‘Honglong’ fruit (A, C, E for winter fruit and B, D, F for summer fruit) that stored in different temperature condition (0, 3, 5, 10 ◦ C). The hairline in each storage day was LSD value at p < 0.05.
The chroma of the summer fruits increased gradually after 28 days of storage at 0 and 3 ◦ C. However, the chroma of the summer fruits gradually became lower after storage for 28 days at 5 and 10 ◦ C; this might be attributable to the fruits turning yellow normally (Fig. 4C and D). At the four temperatures, the hue value of the winter and summer fruits gradually decreased with the storage time. In addition, the hue value of fruits stored at 10 ◦ C was lower than that of fruits stored at the other three temperatures, indicating that fruits stored at 10 ◦ C turn yellow earlier than the others (Fig. 4E and F). At all four temperatures, the firmness of fruits gradually decreased during storage period; in particular, those stored at 10 ◦ C exhibited the most notable decline, whereas the fruits stored at the other three temperatures remained relatively firm (Fig. 5A and B). The TSS in the winter fruits stored at the four temperatures did not
appear to change. The TSS in the summer fruits stored for 35 days at 10 ◦ C was 5.3◦ Brix, which is lower than that of the summer fruits stored at the other three temperatures; this might be attributable to the high respiration rate caused a high consumption of carbohydrates (Fig. 5C and D). The TA of the winter fruits stored at the four temperatures gradually became lower with the storage time; however, storing the fruit at 0 and 3 ◦ C delayed the reduction in TA (Fig. 5E). The TA of the summer fruits gradually increased during the early storage period and then gradually became lower after 14–21 days of storage (Fig. 5F). Winter and summer fruits stored at 0, 3, and 5 ◦ C for 8, 12, 14 days showed evidence of CI; in addition, the CI index increased with the storage time (Fig. 6). The fruits stored at 10 ◦ C also exhibited CI symptoms. In other words, the winter (or summer) fruits
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Fig. 6. The CI index of ‘Honglong’ fruits (winter and summer fruit) that stored in different temperature condition (0, 3, 5, 10 ◦ C). Each value is presented as the mean of four replicates.
stored at 10 ◦ C for 26 days (or 22 days) showed evidence CI symptoms; however, the CI index at 10 ◦ C was lower than those observed at the other storage temperatures. The storage life and shelf life of the fruits stored at the various temperatures were investigated. The longest storage life for the winter fruits was for those stored at 3 ◦ C (38.0 days) and 5 ◦ C (39.2 days); for the summer fruits, the longest storage life was for those stored at 5 ◦ C (40.4 days) (Table 3). By storage temperature, the shortest storage life was observed in the fruits stored at 10 ◦ C (winter: 35.0 days, summer: 32.2 days); the main reasons was rot and the fruit turning yellow. The storage life experiments for the fruits stored at 0 ◦ C were concluded mainly because of CI. Among the four storage temperatures, the longest storage life was attained by the winter and summer fruits stored at 5 ◦ C; the shelf life of fruit stored at 5 ◦ C had also good performance. 4. Discussion The study results indicate that the lightness, chroma and firmness of ‘Honglong’ fruits harvested in summer are superior to those harvested in winter; the fruits at 70% or 80% maturity were of higher quality that those at 60% maturity (Table 1). At 60% maturity, the TSS was low but the TA was high. The winter fruits had a longer storage life compared with the summer fruits with the exception of 60% maturity level (Table 2). During storage, the change in quality was more apparent in the summer fruits than in the winter fruits. In addition, fruits at 60% maturity were more susceptible to CI and had a shorter storage life and shelf life compared with those at 70% or 80% maturity (Table 2). Thus, ‘Honglong’ fruits at 70% maturity
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are of excellent quality and exhibit highly favorable storage characteristics. Among the various storage temperatures, 5 ◦ C resulted in the longest storage life and shelf life. Various carambola species are harvested in various regions worldwide. According to Saúco et al. (1993) and Nakasone and Paull (1998), the main cultivars are ‘Arkin,’ ‘Golden Star,’ ‘Newcomb,’ ‘Thrayer,’ and ‘B10’ for Florida; ‘Sri Kembangsaan’ and ‘Kary’ for Hawaii; ‘Kaput,’ ‘Ting Go,’ and ‘Demak’ for Indonesia; ‘Hong Hug’ and ‘Far Dee’ for China; ‘Chang Tsey’ for Taiwan; ‘B2,’ ‘B10,’ and ‘B17’ for Malaysia; ‘Arkin,’ ‘B1,’ ‘B6,’ ‘B10,’ and ‘Jungle Gold’ for Australia; and ‘Fwang Tung’ and ‘Thai Knight’ for Thailand. In recent years, ‘Honglong’ has become one of the main species cultivated for commercial purposes in Taiwan. Because of differences between target markets and eating habits, different carambola species are cultivated in different countries. Generally, consumers prefer firm, crisp, and juicy carambola fruits with a yellow peel and no brown spots on the peel or ribs. The taste of carambola fruits depends on the species and level of maturity (Kader, 2009). When the fruit ripens, the peel color changes from green to yellow-green and then become yellow or orange as the carbohydrates and TSS increase and organic acids are reduced (Campbell, 1989). Numerous studies on when to harvest carambola fruits have been conducted, but their results have been inconsistent. Some studies have suggested that the fruit should be harvested when they become bright green and a quarter of the peel turns yellow (Miller and McDonald, 1997; Oslund and Davenport, 1983; Paull and Chen, 2014; Warren et al., 2007); other studies have suggested that the fruit should be harvested when half to three-quarters of the peel turns yellow (Pauziah et al., 2009; Tongchitpakdee, 2012). The quality of green carambola fruits typically does not vary substantially; after harvest, the green carambola changes color, and a change from green to yellow coincides with a reduction in firmness. Once this occurs, the fruit can be easily damaged, rendering it unsuitable for packaging and transportation (Oslund and Davenport, 1983; Paull and Chen, 2014; Tongchitpakdee, 2012). Therefore, carambola fruits harvested while still green should have excellent quality, firmness, and storage and transportation characteristics. The ripen stage of ‘B10 carambola fruit significantly affected skin color (chroma and hue value), pH and sensory attributes of color and flavor of the minimally processed of carambola (Ding et al., 2007).The fruits became more than 50% softer as they matured, from 30.5 N at 60% maturity to 14.0 N once the fruit is over-ripe. When the fruits turns yellow and becomes ripe, the structure of cell walls changes; at 60% maturity, cellulose accumulates and hemicellulose and pectin would gradually become lower (Chin et al., 1999). In the present study, the winter and summer fruits at 60% maturity were significantly firmer than those at 70% and 80% maturity (Fig. 2); in all cases, the fruits gradually lost their firmness as they matured. These results accord with those reported in previous studies. Regarding postharvest processing, because the firmness of fruits at 60% maturity was high, these fruits would not be easily damaged during harvesting and packaging. As indicated by Narain et al. (2001), before being harvested, carambola fruits accumulate carbohydrates, their color changes from green to orange, and they become sweet to taste. Furthermore, the TSS content increases as the fruit matures, with higher TSS content at 70% maturity than at 60% maturity. Warren et al. (2007) investigated the quality as well as the storage and transportation characteristics of ‘Arkin’ fruits during their color-break, half-yellow, and fully yellow periods. They found that the TSS gradually increased as the fruit matured (color-break: 6.7◦ Brix, half-yellow: 7.1◦ Brix, and fully yellow: 7.9◦ Brix). In the present study, the TSS in the winter and summer fruits at 80% maturity was high and increased with the fruit maturity (Fig. 2). However, during the storage period, no increase in TSS was observed with the excep-
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Table 3 The storage life and shelf life of ‘Honglong’ fruit that were harvested in winter and summer stored at different temperature. Season
Temperature (◦ C)
Storage life (day)
Winter
0 3 5 10
37.0 ± 1.2bcz Ay 38.0 ± 0.0abA 39.2 ± 0.8aA 35.0 ± 0.0cA 2.192 34.6 ± 0.6cA 37.6 ± 1.1bA 40.4 ± 1.1aA 32.2 ± 0.7cB 2.772
LSD value Summer
LSD value
0 3 5 10
Shelf life (day) 7D
14D
21D
28D
35D
7.2 ± 0.8bz 9.4 ± 1.7ab 11.8 ± 0.7a 11.0 ± 0.0a 2.975 10.2 ± 0.7a 9.8 ± 0.9a 11.6 ± 0.2a 11.4 ± 0.4a 1.896
4.8 ± 0.5c 5.2 ± 0.5bc 7.8 ± 0.7a 6.8 ± 0.8ab 1.931 9.0 ± 0.9a 10.6 ± 0.6a 9.8 ± 0.5a 9.4 ± 0.2a 1.872
4.4 ± 0.4b 4.0 ± 0.0b 6.0 ± 0.0a 6.0 ± 0.0a 0.599 5.6 ± 0.4b 7.8 ± 0.5a 7.8 ± 0.7a 8.4 ± 0.2a 1.499
3.6 ± 1.0a 4.2 ± 0.7a 6.4 ± 0.2a 4.8 ± 0.7a 2.172 4.2 ± 0.2b 5.6 ± 0.2a 5.2 ± 0.6ab 5.4 ± 0.2a 1.06
3.8 ± 0.5bc 3.4 ± 0.4c 4.6 ± 0.4ab 5.0 ± 0.0a 1.121 4.0 ± 0.0a 4.8 ± 0.3a 4.8 ± 0.7a 3.6 ± 0.6a 1.528
z Each value is presented as the mean. The means in same season with the same lowercase letter did not differ significantly at p < 0.05 using least significant difference test. y The means of storage life in same storage temperature between winter and summer with the same capital letter did not differ significantly at p < 0.05 using least significant difference test. The LSD value for 0 ◦ C between winter and summer was 3.145, for 3 ◦ C between winter and summer was 2.588, for 5 ◦ C between winter and summer was 3.178, and for 10 ◦ C between winter and summer was 1.694.
tion of summer fruit of 80% maturity. Therefore, the TSS during the harvesting period is a crucial factor that influences consumer pReferences As indicated by Campbell (1989), as carambola fruit matures, the amount of TA becomes significantly lower and the pH value increases slightly. Warren et al. (2007) collected ‘Arkin’ fruits during their color-break, half-yellow, and fully yellow periods and found that the TA became lower as the fruits matured (color-break: 0.28%, half-yellow: 0.31%, and fully yellow: 0.25%). Mustafa et al. (2016) stored ‘B10’ carambola fruits at 6 ◦ C, the TA content of fruit also peaked on the 8th day of storage. El-Anany et al. (2009) conducted an apple storage test and found that organic acids (e.g., malic acid or citric acid) were the reaction matrix for respiration function; as respiration increased, the TA in the fruits reduced. In the present study, the TA in the fruits at all three maturity levels gradually decreased with fluctuations (Fig. 2). Therefore, during long-term storage, the respiration of carambola fruits might consume organic acids, thereby reducing the TA of the fruits. Fruits might not develop fully or their storage life may be shortened if they are not harvested at the appropriate time (Kader, 1999, 2002). Indian jujubes can naturally ripen on the tree, but their shelf life is short; the optimal harvest time is just as they begin ripening (Abbas, 1997). Pauziah et al. (2009) indicated that if carambola fruits are harvested at 60% maturity, mechanical damage can be reduced and their storage life can be extended. Among the maturity levels, 70% to 80% maturity was associated with the longest storage life; ‘Honglong’ fruits at 60% maturity are sensitive to low temperatures and are thus susceptible to CI (Fig. 3), hence their short storage life. Miller and McDonald (1997) subjected mature green and slightly yellow ‘Arkin’ fruits stored at a low temperature to quarantine treatment at 1 ◦ C for 15 days. They found that mature green fruits experienced more severe peel scald, pitting, stem-end breakdown, and fin browning than did the slightly yellow fruits. Wan and Lam (1984) stored unripened and ripened ‘B10’ carambola fruits at 5, 10, 15, and 20 ◦ C and observed CI on the unripened fruits (i.e., less than one-quarter of their peel had turned yellow) stored at 5 ◦ C for 5 weeks, and this became more severe at longer storage times. Numerous studies in addition to the present study have shown that carambola fruits at a low maturity level are sensitive to low temperatures, which render them susceptible to CI and a short storage life that cannot be extended. Numerous studies have suggested that the optimal storage temperature for carambola fruits should be 7–10 ◦ C; at these temperatures, the storage life is approximately 3–5 weeks (Cantwell, 2002; Dodd and Bouwer, 2014). Currently, exporters in Taiwan set container temperatures to 3–5 ◦ C when storing and transporting carambola fruits. In the present study, we investigated the optimal
storage temperature for ‘Honglong’ fruits; the temperatures were 0, 3, 5, and 10 ◦ C. Numerous studies have indicated that carambola fruits stored below 5 ◦ C exhibit CI, the severity of which increases with the storage time (Ali et al., 2004; Miller and McDonald, 1997; Wan and Lam, 1984; Warren et al., 2007). The CI symptoms on carambola fruits include dark brown concave spots (<1 mm) on the fruit peel surface, large brownish spots (1–2 mm), and rib-edge browning. Kader (2009) indicated that some carambola species stored at 0 ◦ C for 2 weeks or at 5 ◦ C for 6 weeks exhibited CI after being stored for 2 days at 20 ◦ C. In the present study, fruits exhibited CI at all four temperatures, with injury occurring earlier at lower storage temperatures. ‘Honglong’ fruits exhibited CI after storage at 10 ◦ C for 22–26 days (Fig. 6). Ali et al. (2004) observed CI in ‘B10’ fruits stored at 5 and 10 ◦ C; specifically, only 9% of the fruits stored for 25 days at 10 ◦ C exhibited injury, but all of the fruits stored for 40 days at 10 ◦ C exhibited injury. Pérez-Tello et al. (2001) investigated the CI to ‘Yau’ fruits stored at 2, 10, and 20 ◦ C and found those stored at 2 and 10 ◦ C exhibited CI; in addition, the onset of CI was related to peroxidase and phenylalanine ammonia-lyase activity. The influence of storage temperature on vegetable and fruit quality depends on their metabolic rate. Fruit chlorophyll degradation and increased enzyme activity promote color change in fruits (Amir-Shapira et al., 1987). In the present study, the hue value of the winter fruits stored at 5 ◦ C remained higher than 100◦ (Fig. 4). Lam and Wan (1987) indicated that the rate of color change depends on the storage temperature, and the color remains for fruits stored at 5 ◦ C after harvest. Ali et al. (2004) indicated that compared with modified atmosphere packaging, using a lower storage temperature was effective for delaying the onset of color change in ‘B10 fruits. In the present study, the summer fruits maintained their color when stored at 5 ◦ C. O’Hare (1993) indicated that carambola fruits could prevent rib scald when stored for 4 weeks at 10 ◦ C; in addition, carambola fruits could remain unchanged for 5 weeks at 0 and 4 ◦ C. O’Hare (1993) also indicated that at high temperatures, carambola fruits could turn yellow at the same time that chlorophyll degradation occurs. In the present study, the winter fruits retained their firmness when stored at 0 ◦ C after 28th day, and the summer fruits stored at 5 ◦ C generally exhibited high firmness (Fig. 5). Ali et al. (2004) indicated that storing carambola fruits at 5 ◦ C and 85% to 95% relative humidity effectively prevents water loss and promotes firmness. Compared with the quality of completely ripened carambola fruit, that at 70% and 80% maturity is superior (Paull and Chen, 2014). Storage at a low temperature can reduce the respiration rate and thermal decomposition rate and maintain the freshness and shelf life of products (Cheng and Shewfelt, 1988). In the present study, the storage life of the fruits stored at 5 ◦ C was significantly longer
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than the fruits stored at 10 ◦ C (Table 3). The shelf life of the winter fruits stored at 5 ◦ C was relatively long; that of the summer fruits stored at 3 and 5 ◦ C was also relatively long during the late-storage period (Table 3). Although carambola fruits are tropical, they can be stored at 4–5 ◦ C under 90% to 95% relative humidity for 21–35 days (Kader, 1999). According to Pauziah et al. (2009), carambola fruits at the advance maturity stage can be stored for 8 weeks at 8 ◦ C. In Taiwan, ‘Honglong’ fruits are produced throughout most of the year; the color and quality of summer fruits are superior to those of winter fruits; ‘Honglong’ fruits at 70% maturity are bright green-yellow, high in TSS, low in TA, and exhibit excellent quality that accepted by consumers; in addition, their storage life and cold resistance at 70% maturity are superior those at 60% maturity. A storage and transportation temperature of 5 ◦ C was found to be optimal for maintaining the food quality, storage life, and shelf life; storage temperatures of 0 and 3 ◦ C caused severe CI; a storage temperature of 10 ◦ C made the fruits rapidly turn yellow and become rotten. Therefore, we suggest that ‘Honglong’ fruits be harvested at 70% maturity and be stored at 5 ◦ C for commercial purposes. References Abbas, M.F., 1997. Jujube. In: Mitra, K.S. (Ed.), Post-harvest Physiology and Storage of Tropical and Subtropical Fruits. CAB International, Wallingford, pp. 405–415. Ali, Z.M., Chin, L.H., Marimuthu, M., Lazan, H., 2004. Low temperature storage and modified atmosphere packaging of carambola fruit and their effects on ripening related texture changes, wall modification and chilling injury symptoms. Postharvest Biol. Technol. 33, 181–192, http://dx.doi.org/10.1016/j. postharvbio.2004.02.007. Amir-Shapira, D., Goldschmidt, E.E., Altman, A., 1987. Chlorophyll catabolism in senescing plant tissues: in vivo breakdown intermediates suggest different degradative pathways for citrus fruit and parsley leaves. Proc. Natl. Acad. Sci. U. S. A. 84, 1901–1905, http://dx.doi.org/10.1073/pnas.84.7.1901. Ashok, R., Shoba, H., Chidanand, D.V., 2011. A study on shelf life extension of carambola fruits. Int. J. Sci. Eng. Res. 2, 1–5. Braman, K., Ahmad, S., Siddiqui, M.W., 2015. Factors affecting the quality of fruits and vegetables. In: Siddiqui, M.W. (Ed.), Postharvest Biology and Technology of Horticultural Crops. CRC Press, Boca Raton, FL, pp. 1–50. Campbell, C.W., 1989. Carambola production in the United States. Proc. Inter.—Am. Soc. Trop. Hort. 33, 47–54. Cantwell, M.I., 2002. Appendix: summary table of optimal handling condition for fresh produce. In: Kader, A.A. (Ed.), Postharvest Technology of Horticultural Crops. University of California, Richmond, CA, pp. 511–518. Cheng, T.S., Shewfelt, R.I., 1988. Effect of chilling exposure of tomatoes during subsequent ripening. J. Food Sci. 53, 1160–1162, http://dx.doi.org/10.1111/j. 1365-2621.1988. tb13552.x. Chin, L.H., Ali, Z.M., Lazan, H., 1999. Cell wall modifications, degrading enzymes and softening of carambola fruit during ripening. J. Exp. Bot. 50, 767–775, http://dx.doi.org/10.1093/jxb/50.335.767. Ding, P., Ahmad, S.H., Ghazali, H.M., 2007. Changes in selected quality characteristics of minimally processed carambola (Averrhoa carambola L.) when treated with ascorbic acid. J. Sci. Food Agric. 87, 702–709. Dodd, M.C., Bouwer, J.J., 2014. The supply value chain of fresh produce from field to home: refrigeration and other supporting technology. In: Florkowski, W.J., Prussia, S.E., Shewfelt, R.L., Brueckner, B. (Eds.), Postharvest Handling: A Systems Approach. Acadcmic Press, San Diego, CA, pp. 449–483. El-Anany, A.M., Hassan, G.F.A., Rehab Ali, F.M., 2009. Effects of edible coatings on the shelf-life and quality of Anna apple (Malus domestica Borkh) during cold storage. J. Food Technol. 7, 5–11. Kader, A.A., 1999. Fruit maturity ripening and quality relationships. Acta Hort. 485, 203–208, http://dx.doi.org/10.17660/ActaHortic.1999.485.27.
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Kader, A.A., 2002. Postharvest biology and technology: an overview. In: Kader, A.A. (Ed.), Postharvest Technology of Horticulture Crops. , third ed. University of California Agriculture and Natural Resources Publication, California, pp. 39–47. Kader, A.A., 2009. Carambola, http://postharvest.ucdavis.edu/produce/ producefacts/index.html (Accessed 5 December 16). Lam, P.F., Wan, C.K., 1987. Ethylene and carbon dioxide production of starfruits (Averrhoa carambola L.) stored at various temperatures and in different gas and relative humidity atmospheres. Trop. Agric. 64, 181–184. Liu, P.C., 2009. New cultivar of carambola: the breeding of ‘Tainung No. 4’ (Jinglong). Harvest 59, 37–40. McGuire, R.G., 1992. Reporting of objective color measurements. HortScience 27, 1254–1255. Miller, W.R., McDonald, R.E., 1997. Carambola quality after ethylene cold treatments and storage. HortScience 32, 897–899. Morton, J., 1987. Carambola (Averrhoa carambola L.). In: Morton, J.F. (Ed.), Fruit of Warm Climates. Southern Book Service, Miami, FL, pp. 125–128. Mustafa, M.A., Ali, A., Seymour, G., Tucker, G., 2016. Enhancing the antioxidant content of carambola (Averrhoa carambola) during cold storage and methyl jasmonate treatments. Postharvest Bio. Technol. 118, 79–86. Nakasone, H.Y., Paull, R.E., 1998. Tropical Fruits. CAB International, Oxon, UK, p. 608. Narain, N., Holschuh, H., Vasconcelos, M., 2001. Physical and chemical composition of carambola fruit (Averrhoa carambola L.) at three stages of maturity. Cienc. Tecnol. Aliment. 3, 144–148, http://dx.doi.org/10.1080/11358120109487721. O’Hare, T.J., 1993. Postharvest physiology and storage of carambola (starfruit): a review. Postharvest Biol. Technol. 2, 257–267, http://dx.doi.org/10.1016/09255214(93)90031-W. Oslund, C.R., Davenport, T.L., 1983. Ethylene and carbon dioxide in ripening fruit of Averrhoa carambola. HortScience 18, 229–230. Pérez-Tello, G.O., Silva-Espinoza, B.A., Vargas-Arispuro, I., Briceno-Torres, B.O., Martinez-Tellez, M.A., 2001. Effect of temperature on enzymatic and physiological factors related to chilling in carambola fruit (Averrhoa carambola L.). Biochem. Bio. Res. Commun. 287, 846–851, http://dx.doi.org/10.1006/bbrc. 2001.5670. Paull, R.E., Chen, C.C., 2014. Carambola: Postharvest Quality—Maintenance Guidelines. College of tropical agriculture and human resources, University of ¯ Hawaii, Manoa. Pauziah, M., Tarmizi, S.A., Mohd Salleh, P., Norhayati, M., 2009. Quality of starfruit harvested at advanced maturity stage. Acta Hort. 880, 231–236. Peirce, L.C., 1987. Vegetables: Characteristics, Production and Marketing. John Wiley and Sons, New York. Saúco, V.G., Menini, U.G., Tindall, H.D., 1993. Carambola Cultivation. FAO Plant Production and Protection Paper 108, FAO, Rome, pp. 1–74. Siddiqui, M.W., Dhua, R.S., 2010. Eating artificially ripened fruits is harmful. Curr. Sci. 99, 1664–1668. Teixeira, G.H.A., Durigan, J.F., Alves, R.E., O’Hare, T.J., 2008. Response of minimally processed carambola to chemical treatments and low-oxygen atmospheres. Postharvest Bio. Technol. 48, 415–421. Tongchitpakdee, S., 2012. Longan and carambola. In: Siddiq, M. (Ed.), Tropical and Subtropical Fruits: Postharvest Physiology, Processing and Packaging. John Wiley & Sons, Inc, Oxford, pp. 223–240. Wan, C.K., Lam, P.F., 1984. Biochemical changes use of polyethylene bags, and chilling injury of carambola (Averrhoa carambola L.) stored at various temperature. Pertanika 7, 39–46. Warren, O., Sargent, S.A., Pereira, M.E., Berry, A.D., 2007. Harvesting carambola at different ripeness stages affects postharvest quality. Proc. Fla. State Hort. Soc. 120, 256–258. Wu, J.S.B., Sheu, M.J., Fang, T.T., 1993. Oriental fruit juices: carambola, Japanese apricot (mei), lychee. In: Chen, S. Nagy, C.S. Shaw, P.E. (Eds.), Fruit Juice Processing Technology. AgScience, Auburndale, FL. Wu, J.S., Wu, M.S., Wei, P., 2004. Tropical fruits. In: Barrett, D.M., Somogyi, L., Ramaswamy, H.S. (Eds.), Processing Fruits: Science and Technology. , second ed. CRC Press, Boca Raton, FL, pp. 679–705. Yan, S.W., Ramasamy, R., Alitheen, N.B.M., Rahmat, A., 2013. A comparative assessment of nutritional composition, total phenolic, total flavonoid, antioxidant capacity, and antioxidant vitamins of two types of malaysian underutilized fruits (Averrhoa Bilimbi and Averrhoa Carambola). Int. J. Food Prop. 16, 1231–1244.
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Scientia Horticulturae journal homepage: www.elsevier.com/locate/scihorti
Effect of harvest season, maturity and storage temperature on storability of carambola ‘Honglong’ fruit Shao-Wei Chen a , Min-Chi Hsu b , Hsin-Hsiu Fang c , Shang-Han Tsai a , Yu-Shen Liang a,∗ a
Department of Plant Industry, National Pingtung University of Science and Technology, No.1, Shuefu Rd., Neipu, Pingtung 91201, Taiwan, ROC Crop Science Division, Taiwan Agricultural Research Institute, No.189, Zhongzheng Rd., Wufeng Dist., Taichung City 41362, Taiwan, ROC Department of Tropical Fruit Tree, Fengshan Tropical Horticultural Experiment Branch, Taiwan Agricultural Research Institute, No. 530, Wenlong E. Rd., Fengshan Dist., Kaohsiung City 830, Taiwan, ROC b c
a r t i c l e
i n f o
Article history: Received 18 January 2017 Received in revised form 22 March 2017 Accepted 24 March 2017 Available online 31 March 2017 Keywords: Chilling injury Titratable acidity Total soluble solids Storage life Shelf life
a b s t r a c t Averrhoa carambola L. cv. Honglong is a species newly bred in Taiwan for commercial purposes. However, few studies have been conducted on the storage and transportation of this fruit. Accordingly, the present study investigated the influences of harvest reasons, fruit maturity, and storage temperature on the food quality and storage life of ‘Honglong’ fruits. The results showed that the color and firmness of summer fruits were superior to those of winter fruits; the winter fruits at 70% or 80% maturity had a significantly longer the storage life than the corresponding summer fruits. Fruits with 70% maturity (i.e., when half of the fruit is yellow) are bright green-yellow, high in total soluble solids (7.1◦ Brix for winter fruits and 7.5◦ Brix for summer fruits), and low in titratable acidity (0.34% for winter fruits and 0.32% for summer fruits). In addition, the storage life and cold resistance of fruits with 70% maturity had a longer life and were more resistant to cold than those with 60% maturity were. The transportation storage temperature of 5 ◦ C caused slight chilling injury but was optimal for maintaining food quality, storage life, and shelf life. Storage temperatures of 0 and 3 ◦ C caused severe chilling injury, and 10 ◦ C caused the fruits to rapidly turn yellow and rot. We suggest that ‘Honglong’ fruits be harvested at 70% maturity and be stored at 5 ◦ C to achieve optimal quality for commercial production. © 2017 Elsevier B.V. All rights reserved.
1. Introduction Averrhoa carambola L. cv. Honglong is a member of the Oxalidaceae family. Carambola fruit is oval or elliptical with three to five longitudinal ribs. The fruit derives its vernacular name “starfruit” from its star-shaped cross section; it was a potent natural antioxidant food and contained abound in phenolic compounds (Tongchitpakdee, 2012; Yan et al., 2013). Carambola fruit has a sour tart or mildly sweet taste depending on the species and level of maturity. The fruit can be eaten fresh or after processing (Morton, 1987; Wu et al., 2004). Prior to 2010, the main cultivars of carambola fruits exported from Taiwan was Averrhoa carambola L. cv. Chang Tsey (‘Chang Tsey’ carambola), accounting for 40% of carambola fruit exports. In recent years, ‘Chang Tsey’ carambola crops were often damaged by pests and disease, and the frequent use of pesticide increased production costs. Accordingly, the agricultural area for cultivating
∗ Corresponding author. E-mail addresses: [email protected] (S.-W. Chen), [email protected] (M.-C. Hsu), [email protected] (H.-H. Fang), [email protected] (S.-H. Tsai), [email protected] (Y.-S. Liang). http://dx.doi.org/10.1016/j.scienta.2017.03.047 0304-4238/© 2017 Elsevier B.V. All rights reserved.
‘Chang Tsey’ carambola gradually reduced, and another species, ‘Honglong,’ became dominant for cultivation. Fengshan Tropical Horticultural Experiment Branch first cultivated ‘Honglong’ with self-seedlings obtained from the species ‘Jakarta.’ The peel of the fruit is orange-red and has thick, firm ribs; it is considered delicious, suitable for storage and transportation, and is therefore preferred by for export. Currently, ‘Honglong’ carambola is the main species exported from Taiwan (Liu, 2009). When managed properly, carambola fruits can be harvested three times annually (Wu et al., 1993). In Florida, carambola fruits are harvested from June to February; however, the main harvest periods are August–October and December–February. In Malaysia, the fruit is harvested throughout most of the year; however, the main harvest periods are April–May, July–August, and November–December (Tongchitpakdee, 2012). In Taiwan, except for the low harvest from May to July, most harvests during other periods are exported. Product quality and nutritional quality are influenced by the climate. For example, lettuce is typically grown at low temperatures and has a firm head with a mild flavor. If lettuce is grown at high temperatures or during droughts, its leaves will be less tender even if the flavor quality of the head excellent (Peirce, 1987).
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Harvest maturity is crucial for quality management and has a marked influence on product quality (Braman et al., 2015). It can also influence the metabolic responses of vegetables and fruits. Therefore, it is a crucial factor that determines product quality, storage potential, and storage disorder (O’Hare, 1993; Siddiqui and Dhua, 2010). Currently, to prevent mechanical damage to carambola fruits during long-distance transportation and after-harvest handling, exporters suggest that the fruit should be harvested at the color-break stage (O’Hare, 1993). Because total soluble solids (TSS) content in carambola fruits increases with maturity, Warren et al. (2007) suggested that the fruit of Averrhoa carambola L. cv. Arkin (‘Arkin’ carambola) should be harvested after the color-break stage to ensure excellent food quality. Cold storage is commonly used to transport fruits to international markets, however, tropical fruits are susceptible to chilling injury (Mustafa et al., 2016). The influence of storage temperature on the quality of fruits and vegetables depends on the metabolic rates of them. Dodd and Bouwer (2014) suggested that the optimum temperature and relative humidity for storage of carambola fruits were 7–10 ◦ C and 85–95%, respectively. Under these conditions, the storage life of the fruits is approximately 21–35 days. Cantwell (2002), however, suggested that the optimum storage temperature and relative humidity were 9–10 ◦ C and 85% to 90%, respectively. Under these conditions, the storage life of the fruit is approximately 3–4 weeks. Numerous reports have indicated that for this fruit, storage temperature ≤5 ◦ C causes chilling injury (CI), which becomes severe with longer storage times (Miller and McDonald, 1997; Wan and Lam, 1984; Warren et al., 2007). ‘Honglong’ is a newly bred species that has been widely accepted by farmers and consumers in Taiwan. Furthermore, it has become a major carambola cultivar. However, few studies have examined the physical, storage, and transportation characteristics of this cultivar to derive a reference for business operators regarding the optimum storage and transportation conditions. Accordingly, in the present study, the influences of the harvest season, fruit maturity, and storage temperature on the fruit quality and storage life of ‘Honglong’ were investigated.
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CI index were investigated. At 7, 14, 21, 28, 35, and 42 days, fruits were stored at 25 ◦ C to investigate their shelf life. Each analysis was carried out 5 replications and each replication included two fruit samples. 2.2. Experiment II. Storage temperature During winter (February 4th) and summer (August 27th) in 2013, fruits having 70% maturity were harvested and sent to the laboratory. The 70% maturity of carambola is mainly harvest maturity for commercial exportation in Taiwan. Fruits were removed if they were over- or under-ripened or affected by pests, disease, or mechanical damage. The remaining fruits were stored in a refrigerator at 0, 3, 5, or 10 ◦ C and their storage life, chilling injuring index, and quality investigated. After 7, 14, 21, 28, 35, and 42 days of storage, the fruits were then stored at 25 ◦ C and their shelf life was investigated. Each analysis was carried out 5 replications and each replication included two fruit samples. 2.3. Quality characteristics 2.3.1. Color The color of the rib peel was determined at three points (top, middle, bottom) and a mean value was calculated for each piece of fruit. A color difference meter (ZE-2000, Nippon Denshoku) was used to measure the lightness and to obtain the values of a and b. The lightness values ranged from 0 to 100, with lower values representing darker colors. Hue value ( value = tan−1 |b/a|) was used to represent the color change in the fruit (0◦ = red-purple, 90◦ = yellow, 180◦ = blue-green, and 270◦ = blue). Color intensity was represented by C = [(a2 + b2 )1/2 ], with higher values indicating higher color intensity (McGuire, 1992). 2.3.2. Firmness A property analyzer EZ-test 500N, Shimadzu with a No. 5 probe (diameter, 5 mm) was employed to measure the fruit firmness. The probe depth was set to 10 mm. Measurements (N) were performed at the top, middle, and bottom parts of the ribs, and a mean value was calculated for each piece of fruit.
2. Materials and methods 2.1. Experiment I. Harvest maturity ‘Honglong’ fruits were harvested in Ligang Township (Pingtung County, Taiwan) during winter (February 26th) and summer (September 10th) in 2012. Fruit maturity was determined through visual inspection, and three levels of maturity were determined: 60% maturity (one-quarter of the fruit had turned yellow), 70% maturity (half of the fruit had turned yellow), and 80% maturity (three-quarters of the fruit had turned yellow). The inspection criteria are defined as follows: 60% maturity: the fruit is not fully developed, the outer edge of its ribs appear dark green, and the ribs appear light green (approximately 65–75 days after blossoming for summer fruits and approximately 100–110 days after blossoming for winter fruits); 70% maturity: the fruit is fully developed, the outer edge of its ribs appear light green, and approximately half of its ribs are yellow (approximately 70–80 days after blossoming for summer fruits and approximately 105–115 days after blossoming for winter fruits); and 80% maturity: the color of a fruit has begun changing, but the outer edge of its ribs remain green (approximately 80–90 days after blossoming for summer fruits and approximately 115–125 days after blossoming for winter fruits). The fruits were selected and sent to a laboratory. Fruits were removed if they were over- or under-ripened or affected by pests, disease, or mechanical damage. The remaining fruits were stored in a refrigerator at 5 ◦ C and their storage life, quality, and
2.3.3. Total soluble solid The TSS content in the juice was measured using a hand-hold refractometer N-IE, Atago; the TSS value was presented in ◦ Brix. The TSS of the top, middle, bottom parts of the ribs of each fruit were measured and the mean TSS value was calculated for each fruit. 2.3.4. Titratable acidity Carambola pulp of 10 g was added to 100 mL of distilled water; the mixture liquid was filtered by using filter paper (Whatman No. 1). Subsequently, 25 mL of filtrate was removed and titrated in 0.1 M NaOH. An automatic potentiometric titrator (DL53, Mettler Toledo) was employed to titrate the filtrate until its pH was 8.1. The NaOH titration of the sample was converted into the chemical equivalent of citric acid to obtain the total titratable acidity (TA) (%) of the sample (Teixeira et al., 2008; Ashok et al., 2011). 2.4. Chilling injury Chilling injury (e.g., black or brown depressed spots) due to low temperature was assessed through visual observation. Three CI index were determined (index 0–2). The criteria were defined as follows: CI index 0: the peel is bright and without CI; index 1: the peel exhibits slight CI with brown depressed spots covering less than 20% of the peel; and index 2: the peel shows clear CI with brown depressed spots covering more than 20% of the peel. The CI
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Fig. 1. The lightness, chroma and hue value of ‘Honglong’ fruits (A, C, E for winter fruit and B, D, F for summer fruit) with different maturity that stored at 5 ◦ C condition. The hairline in each storage day was LSD value at p < 0.05.
index was calculated, according to the severity of symptoms and the number of fruit. Fruit with CI index 2 has no commercial value. 2.5. Storage life For each experiment, if half of the fruits stored at low temperature had disease or mildew, had turned completely yellow (90% maturity), exhibited CI index 2, or appeared rotten, the storage life of repetition was concluded because the fruit would not appeal to consumers. Four replicates were conducted for storage life assay, and five fruits were used for each of four replicates. Each treatment was 20 fruits (4 replicates x 5 fruits) totally in each assay. 2.6. Shelf life Some fruits originally stored at low temperature were removed every second week and placed on a shelf at 25 ◦ C. In each experi-
ment, if half of the fruits had disease or mildew, turned completely yellow (90% maturity), exhibited CI index 2, or appeared rotten, the shelf life of repetition was concluded because the fruit would be accepted by the consumers. Three replicates were conducted for shelf life assay, and five fruits were used for each of four replicates. Each treatment was 15 fruits (3 replicates x 5 fruits) totally in each assay.
2.7. Statistical analysis Analysis of variance (ANOVA) was performed on the test data by using the statistical analysis system (SAS), with a least significant difference test at a 5% significance level. Chart plotting was performed using Sigma Plot 10.0 and Microsoft Excel.
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Fig. 2. The firmness, total soluble solids and titrable acidity of ‘Honglong’ fruits (A, C, E for winter fruit and B, D, F for summer fruit) with different maturity that stored at 5 ◦ C condition. The hairline in each storage day was LSD value at p < 0.05.
3. Results 3.1. Experiment I. Harvest maturity The quality characteristics of winter fruits (harvest: February 26th, 2012) and summer fruits (harvest: September 10th, 2012) at 60%, 70%, and 80% maturity were compared at harvest time (Table 1). The color of the fruits at the three maturity levels was compared; the hue value was found to gradually reduce with the maturity. Fruit quality was optimal at 60% maturity, becoming lower as the fruit matured. For both winter and summer fruits, the TSS at 80% maturity (winter: 7.9◦ Brix, summer: 10.3◦ Brix) was significantly higher than that at 60% maturity (winter: 6.9◦ Brix, summer: 7.0◦ Brix) and 70% maturity (winter: 7.1◦ Brix, summer:
7.5◦ Brix). The TA was the highest at 60% and 70% maturity for winter and at 60% maturity level for summer product reducing gradually as the fruit matured. The color of the fruits differed significantly between seasons (Table 1). The summer fruits were significantly brighter and more intense in color at all three maturity levels, whereas the hue value of the winter fruits was higher. In addition, the summer fruits were significantly firmer at all three maturity levels. TSS of 60% and TA of 60% and 80% maturity were significant difference between seasons; however, these results were not consistent across the three maturity levels. For all three maturity levels, we investigated the color and quality of fruits stored at 5 ◦ C. Initially, the lightness gradually decreased and then increased (Fig. 1A and B), whereas the chroma increased
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Table 1 The quality of ‘Honglong’ fruit with different maturities at harvest time. Season
Winter
LSD value Summer
Maturity
60% 70% 80% 60% 70% 80%
LSD value LSD value for 60% LSD value for 70% LSD value for 80%
Coloration
Lightness (L value)
Chroma (C value)
Hue value (degree sign)
23.5 ± 2.5ab B 21.4 ± 3.1bB 25.7 ± 2.4aB 2.857 38.1 ± 1.8aA 32.8 ± 2.2bA 34.2 ± 1.5bA 2.082 2.573 2.972 2.183
8.1 ± 1.2aB 7.7 ± 0.8aB 8.0 ± 1.1aB 1.235 12.6 ± 1.2bA 10.7 ± 1.6cA 15.1 ± 0.7aA 1.203 1.348 1.388 0.928
118.5 ± 6.5aA 115.0 ± 5.9aA 100.8 ± 8.6bA 7.840 112.9 ± 3.3aB 116.0 ± 3.9aA 92.2 ± 6.2bB 5.299 5.931 5.988 8.122
z
y
Firmness (N)
Total soluble solids (◦ Brix)
Titratable acidity (%)
13.8 ± 1.1aB 12.2 ± 1.1bB 11.0 ± 1.1cB 1.224 18.5 ± 1.0aA 14.4 ± 1.3bA 12.6 ± 1.4cA 0.823 1.588 1.412 1.549
6.9 ± 0.1bA 7.1 ± 0.3bA 7.9 ± 0.2aB 0.605 7.0 ± 0.2bA 7.5 ± 0.2bA 10.3 ± 0.3aA 0.646 0.454 0.613 0.807
0.31 ± 0.06aB 0.34 ± 0.16aA 0.27 ± 0.05bA 0.039 0.44 ± 0.25aA 0.32 ± 0.09bA 0.17 ± 0.08cB 0.068 0.061 0.060 0.049
z Each value is presented as the mean of four replicates. The means in same season with the same lowercase letter did not differ significantly at p < 0.05 using least significant difference test. y The means in same maturity between winter and summer with the same capital letter did not differ significantly at p < 0.05 using least significant difference test.
with time (Fig. 1C and D). At all three maturity levels, the hue value of the winter fruits gradually reduced after the fruits were stored at 5 ◦ C for 28 days; the hue value of summer fruits at 60% or 70% maturity rapidly decreased after 14 days of storage at 5 ◦ C; the hue value of summer fruits at 80% maturity did not change significantly during storage (Fig. 1E and F). During storage, the fruit gradually became softer with time (Fig. 2A and B). For both the winter and summer fruits, the TSS at 80% maturity was significantly higher than that at 60% or 70% maturity (Fig. 2C and D). The TSS in the summer fruits at 80% maturity increased during the late storage period (Days 35 and 42). The TA of the winter fruits gradually reduced during the late storage period, there were no significantly different at three maturity during storage; at 60% maturity, the TA of summer fruits also reduced during storage period, but that at 70% or 80% maturity did not change significantly (Fig. 2E and F). The TA of the winter fruits became lower during the late storage period; at 70% or 80% maturity, the TA of the summer fruits gradually became lower, but that at 60% maturity did not change significantly (Fig. 2E and F). The fruit of three maturity were stored at 5 ◦ C was investigated for CI during storage.Winter fruits exhibited CI after 12 days of storage at 5 ◦ C; the fastest increase in the CI index was observed in the winter fruits at 60% maturity, the CI index arrived 2 after 36 days of storage (Fig. 3). The CI indices of fruits at 70% and 80% maturity were respectively 1.8 and 1.6 after 42 days of storage. CI to the summer fruits became delayed as their maturity increased; fruits at 60%, 70%, and 80% maturity exhibited CI after storage for 14, 20, and 24 days, respectively. Compared with the winter fruits, the summer fruits exhibited less severe CI. We investigated the storage life and shelf life of the fruits at all three maturity levels. The storage life of the winter fruits at 70% or 80% maturity was significantly longer than that of the winter fruits at 60% maturity (Table 2). The storage life of summer fruit at different maturity stages was not significantly different. The winter fruits at 70% or 80% maturity had a significantly longer the storage life than the corresponding summer fruits; however, there was no difference in storage life between the winter and summer fruits at 60% maturity. To investigate the shelf life, some fruits were removed from lowtemperature storage each week and kept at 25 ◦ C. The shelf life was found to gradually become shorter with the storage time (Table 2). At all three maturity levels, fruits stored for 35 days at 5 ◦ C had a shelf life of approximately 3–5 days. No significant difference in shelf life was observed between the three maturity levels in 35th day of storage. The most limiting factor was rotting in shelf life experiments; after 21 days storage at 5 ◦ C, the fruit easily became rotten or grew mildew when stored at 25 ◦ C.
Fig. 3. The CI index of ‘Honglong’ fruits (winter and summer fruit) with different maturity that stored at 5 ◦ C condition. Each value is presented as the mean of four replicates.
3.2. Experiment II. Storage temperature We investigated the quality and storage characteristics of winter (harvest: February 4th, 2013) and summer (harvest: August 27th, 2013) fruits were stored at 0, 3, 5, and 10 ◦ C. The lightness of the winter fruits increased on 35 and 42 days of storage. The summer fruits became their brightest on 28 days of storage at 5 and 10 ◦ C; their peel brightness rapid reduced because of CI at these storage temperatures (Fig. 4A and B). The winter fruits gradually became more intense in chroma after 35 and 42 days storage at 5, and 10 ◦ C.
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Table 2 The storage life and shelf life of ‘Honglong’ fruit with different maturities that were harvested in winter and summer. Season
Maturity
Storage life (day)
Winter
60% 70% 80%
36.6 ± 0.2bz Ay 42.8 ± 0.4aA 42.6 ± 0.4aA 1.067 34.6 ± 1.8aA 37.2 ± 1.2aB 38.4 ± 1.0aB 4.269
LSD value Summer
LSD value
60% 70% 80%
Shelf life (day) 7D
14D
21D
28D
35D
42D
9.6 ± 1.9a 10.8 ± 0.5a 12.0 ± 0.0a 3.513 9.4 ± 0.2b 10.6 ± 1.3a 13.8 ± 0.7a 2.674
9.2 ± 0.7a 6.4 ± 0.6b 6.4 ± 0.6b 1.996 9.2 ± 0.7a 9.8 ± 0.6a 9.6 ± 1.1a 2.602
4.0 ± 0.0b 7.8 ± 0.5a 7.4 ± 0.4a 1.125 6.4 ± 0.7b 6.0 ± 0.6a 9.6 ± 0.6a 1.882
5.8 ± 0.7a 4.0 ± 0.0b 6.4 ± 0.6a 1.687 5.8 ± 0.4b 5.8 ± 0.2b 7.6 ± 0.6a 1.307
3.2 ± 0.5a 4.6 ± 0.6a 3.6 ± 0.4a 1.550 5.4 ± 0.2a 5.2 ± 0.2a 4.8 ± 0.6a 1.180
x 3.0 ± 0.0b 3.8 ± 0.2a 0.3558 3.0 ± 0.0a 2.6 ± 0.2a 2.2 ± 0.6a 1.125
x, It means the fruits was decay during storage. z Each value is presented as the mean. The means in same season with the same lowercase letter did not differ significantly at p < 0.05 using least significant difference test. y The means of storage life in same maturity between winter and summer with the same capital letter did not differ significantly at p < 0.05 using least significant difference test. The LSD value for 60% maturity between winter and summer was 4.264, for 70% maturity between winter and summer was 2.898, and for 80% maturity between winter and summer was 2.440.
Fig. 4. The lightness, chroma and hue value of ‘Honglong’ fruit (A, C, E for winter fruit and B, D, F for summer fruit) that stored in different temperature condition (0, 3, 5, 10 ◦ C). The hairline in each storage day was LSD value at p < 0.05.
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Fig. 5. The firmness, total soluble solids and titrable acidity of ‘Honglong’ fruit (A, C, E for winter fruit and B, D, F for summer fruit) that stored in different temperature condition (0, 3, 5, 10 ◦ C). The hairline in each storage day was LSD value at p < 0.05.
The chroma of the summer fruits increased gradually after 28 days of storage at 0 and 3 ◦ C. However, the chroma of the summer fruits gradually became lower after storage for 28 days at 5 and 10 ◦ C; this might be attributable to the fruits turning yellow normally (Fig. 4C and D). At the four temperatures, the hue value of the winter and summer fruits gradually decreased with the storage time. In addition, the hue value of fruits stored at 10 ◦ C was lower than that of fruits stored at the other three temperatures, indicating that fruits stored at 10 ◦ C turn yellow earlier than the others (Fig. 4E and F). At all four temperatures, the firmness of fruits gradually decreased during storage period; in particular, those stored at 10 ◦ C exhibited the most notable decline, whereas the fruits stored at the other three temperatures remained relatively firm (Fig. 5A and B). The TSS in the winter fruits stored at the four temperatures did not
appear to change. The TSS in the summer fruits stored for 35 days at 10 ◦ C was 5.3◦ Brix, which is lower than that of the summer fruits stored at the other three temperatures; this might be attributable to the high respiration rate caused a high consumption of carbohydrates (Fig. 5C and D). The TA of the winter fruits stored at the four temperatures gradually became lower with the storage time; however, storing the fruit at 0 and 3 ◦ C delayed the reduction in TA (Fig. 5E). The TA of the summer fruits gradually increased during the early storage period and then gradually became lower after 14–21 days of storage (Fig. 5F). Winter and summer fruits stored at 0, 3, and 5 ◦ C for 8, 12, 14 days showed evidence of CI; in addition, the CI index increased with the storage time (Fig. 6). The fruits stored at 10 ◦ C also exhibited CI symptoms. In other words, the winter (or summer) fruits
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Fig. 6. The CI index of ‘Honglong’ fruits (winter and summer fruit) that stored in different temperature condition (0, 3, 5, 10 ◦ C). Each value is presented as the mean of four replicates.
stored at 10 ◦ C for 26 days (or 22 days) showed evidence CI symptoms; however, the CI index at 10 ◦ C was lower than those observed at the other storage temperatures. The storage life and shelf life of the fruits stored at the various temperatures were investigated. The longest storage life for the winter fruits was for those stored at 3 ◦ C (38.0 days) and 5 ◦ C (39.2 days); for the summer fruits, the longest storage life was for those stored at 5 ◦ C (40.4 days) (Table 3). By storage temperature, the shortest storage life was observed in the fruits stored at 10 ◦ C (winter: 35.0 days, summer: 32.2 days); the main reasons was rot and the fruit turning yellow. The storage life experiments for the fruits stored at 0 ◦ C were concluded mainly because of CI. Among the four storage temperatures, the longest storage life was attained by the winter and summer fruits stored at 5 ◦ C; the shelf life of fruit stored at 5 ◦ C had also good performance. 4. Discussion The study results indicate that the lightness, chroma and firmness of ‘Honglong’ fruits harvested in summer are superior to those harvested in winter; the fruits at 70% or 80% maturity were of higher quality that those at 60% maturity (Table 1). At 60% maturity, the TSS was low but the TA was high. The winter fruits had a longer storage life compared with the summer fruits with the exception of 60% maturity level (Table 2). During storage, the change in quality was more apparent in the summer fruits than in the winter fruits. In addition, fruits at 60% maturity were more susceptible to CI and had a shorter storage life and shelf life compared with those at 70% or 80% maturity (Table 2). Thus, ‘Honglong’ fruits at 70% maturity
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are of excellent quality and exhibit highly favorable storage characteristics. Among the various storage temperatures, 5 ◦ C resulted in the longest storage life and shelf life. Various carambola species are harvested in various regions worldwide. According to Saúco et al. (1993) and Nakasone and Paull (1998), the main cultivars are ‘Arkin,’ ‘Golden Star,’ ‘Newcomb,’ ‘Thrayer,’ and ‘B10’ for Florida; ‘Sri Kembangsaan’ and ‘Kary’ for Hawaii; ‘Kaput,’ ‘Ting Go,’ and ‘Demak’ for Indonesia; ‘Hong Hug’ and ‘Far Dee’ for China; ‘Chang Tsey’ for Taiwan; ‘B2,’ ‘B10,’ and ‘B17’ for Malaysia; ‘Arkin,’ ‘B1,’ ‘B6,’ ‘B10,’ and ‘Jungle Gold’ for Australia; and ‘Fwang Tung’ and ‘Thai Knight’ for Thailand. In recent years, ‘Honglong’ has become one of the main species cultivated for commercial purposes in Taiwan. Because of differences between target markets and eating habits, different carambola species are cultivated in different countries. Generally, consumers prefer firm, crisp, and juicy carambola fruits with a yellow peel and no brown spots on the peel or ribs. The taste of carambola fruits depends on the species and level of maturity (Kader, 2009). When the fruit ripens, the peel color changes from green to yellow-green and then become yellow or orange as the carbohydrates and TSS increase and organic acids are reduced (Campbell, 1989). Numerous studies on when to harvest carambola fruits have been conducted, but their results have been inconsistent. Some studies have suggested that the fruit should be harvested when they become bright green and a quarter of the peel turns yellow (Miller and McDonald, 1997; Oslund and Davenport, 1983; Paull and Chen, 2014; Warren et al., 2007); other studies have suggested that the fruit should be harvested when half to three-quarters of the peel turns yellow (Pauziah et al., 2009; Tongchitpakdee, 2012). The quality of green carambola fruits typically does not vary substantially; after harvest, the green carambola changes color, and a change from green to yellow coincides with a reduction in firmness. Once this occurs, the fruit can be easily damaged, rendering it unsuitable for packaging and transportation (Oslund and Davenport, 1983; Paull and Chen, 2014; Tongchitpakdee, 2012). Therefore, carambola fruits harvested while still green should have excellent quality, firmness, and storage and transportation characteristics. The ripen stage of ‘B10 carambola fruit significantly affected skin color (chroma and hue value), pH and sensory attributes of color and flavor of the minimally processed of carambola (Ding et al., 2007).The fruits became more than 50% softer as they matured, from 30.5 N at 60% maturity to 14.0 N once the fruit is over-ripe. When the fruits turns yellow and becomes ripe, the structure of cell walls changes; at 60% maturity, cellulose accumulates and hemicellulose and pectin would gradually become lower (Chin et al., 1999). In the present study, the winter and summer fruits at 60% maturity were significantly firmer than those at 70% and 80% maturity (Fig. 2); in all cases, the fruits gradually lost their firmness as they matured. These results accord with those reported in previous studies. Regarding postharvest processing, because the firmness of fruits at 60% maturity was high, these fruits would not be easily damaged during harvesting and packaging. As indicated by Narain et al. (2001), before being harvested, carambola fruits accumulate carbohydrates, their color changes from green to orange, and they become sweet to taste. Furthermore, the TSS content increases as the fruit matures, with higher TSS content at 70% maturity than at 60% maturity. Warren et al. (2007) investigated the quality as well as the storage and transportation characteristics of ‘Arkin’ fruits during their color-break, half-yellow, and fully yellow periods. They found that the TSS gradually increased as the fruit matured (color-break: 6.7◦ Brix, half-yellow: 7.1◦ Brix, and fully yellow: 7.9◦ Brix). In the present study, the TSS in the winter and summer fruits at 80% maturity was high and increased with the fruit maturity (Fig. 2). However, during the storage period, no increase in TSS was observed with the excep-
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Table 3 The storage life and shelf life of ‘Honglong’ fruit that were harvested in winter and summer stored at different temperature. Season
Temperature (◦ C)
Storage life (day)
Winter
0 3 5 10
37.0 ± 1.2bcz Ay 38.0 ± 0.0abA 39.2 ± 0.8aA 35.0 ± 0.0cA 2.192 34.6 ± 0.6cA 37.6 ± 1.1bA 40.4 ± 1.1aA 32.2 ± 0.7cB 2.772
LSD value Summer
LSD value
0 3 5 10
Shelf life (day) 7D
14D
21D
28D
35D
7.2 ± 0.8bz 9.4 ± 1.7ab 11.8 ± 0.7a 11.0 ± 0.0a 2.975 10.2 ± 0.7a 9.8 ± 0.9a 11.6 ± 0.2a 11.4 ± 0.4a 1.896
4.8 ± 0.5c 5.2 ± 0.5bc 7.8 ± 0.7a 6.8 ± 0.8ab 1.931 9.0 ± 0.9a 10.6 ± 0.6a 9.8 ± 0.5a 9.4 ± 0.2a 1.872
4.4 ± 0.4b 4.0 ± 0.0b 6.0 ± 0.0a 6.0 ± 0.0a 0.599 5.6 ± 0.4b 7.8 ± 0.5a 7.8 ± 0.7a 8.4 ± 0.2a 1.499
3.6 ± 1.0a 4.2 ± 0.7a 6.4 ± 0.2a 4.8 ± 0.7a 2.172 4.2 ± 0.2b 5.6 ± 0.2a 5.2 ± 0.6ab 5.4 ± 0.2a 1.06
3.8 ± 0.5bc 3.4 ± 0.4c 4.6 ± 0.4ab 5.0 ± 0.0a 1.121 4.0 ± 0.0a 4.8 ± 0.3a 4.8 ± 0.7a 3.6 ± 0.6a 1.528
z Each value is presented as the mean. The means in same season with the same lowercase letter did not differ significantly at p < 0.05 using least significant difference test. y The means of storage life in same storage temperature between winter and summer with the same capital letter did not differ significantly at p < 0.05 using least significant difference test. The LSD value for 0 ◦ C between winter and summer was 3.145, for 3 ◦ C between winter and summer was 2.588, for 5 ◦ C between winter and summer was 3.178, and for 10 ◦ C between winter and summer was 1.694.
tion of summer fruit of 80% maturity. Therefore, the TSS during the harvesting period is a crucial factor that influences consumer pReferences As indicated by Campbell (1989), as carambola fruit matures, the amount of TA becomes significantly lower and the pH value increases slightly. Warren et al. (2007) collected ‘Arkin’ fruits during their color-break, half-yellow, and fully yellow periods and found that the TA became lower as the fruits matured (color-break: 0.28%, half-yellow: 0.31%, and fully yellow: 0.25%). Mustafa et al. (2016) stored ‘B10’ carambola fruits at 6 ◦ C, the TA content of fruit also peaked on the 8th day of storage. El-Anany et al. (2009) conducted an apple storage test and found that organic acids (e.g., malic acid or citric acid) were the reaction matrix for respiration function; as respiration increased, the TA in the fruits reduced. In the present study, the TA in the fruits at all three maturity levels gradually decreased with fluctuations (Fig. 2). Therefore, during long-term storage, the respiration of carambola fruits might consume organic acids, thereby reducing the TA of the fruits. Fruits might not develop fully or their storage life may be shortened if they are not harvested at the appropriate time (Kader, 1999, 2002). Indian jujubes can naturally ripen on the tree, but their shelf life is short; the optimal harvest time is just as they begin ripening (Abbas, 1997). Pauziah et al. (2009) indicated that if carambola fruits are harvested at 60% maturity, mechanical damage can be reduced and their storage life can be extended. Among the maturity levels, 70% to 80% maturity was associated with the longest storage life; ‘Honglong’ fruits at 60% maturity are sensitive to low temperatures and are thus susceptible to CI (Fig. 3), hence their short storage life. Miller and McDonald (1997) subjected mature green and slightly yellow ‘Arkin’ fruits stored at a low temperature to quarantine treatment at 1 ◦ C for 15 days. They found that mature green fruits experienced more severe peel scald, pitting, stem-end breakdown, and fin browning than did the slightly yellow fruits. Wan and Lam (1984) stored unripened and ripened ‘B10’ carambola fruits at 5, 10, 15, and 20 ◦ C and observed CI on the unripened fruits (i.e., less than one-quarter of their peel had turned yellow) stored at 5 ◦ C for 5 weeks, and this became more severe at longer storage times. Numerous studies in addition to the present study have shown that carambola fruits at a low maturity level are sensitive to low temperatures, which render them susceptible to CI and a short storage life that cannot be extended. Numerous studies have suggested that the optimal storage temperature for carambola fruits should be 7–10 ◦ C; at these temperatures, the storage life is approximately 3–5 weeks (Cantwell, 2002; Dodd and Bouwer, 2014). Currently, exporters in Taiwan set container temperatures to 3–5 ◦ C when storing and transporting carambola fruits. In the present study, we investigated the optimal
storage temperature for ‘Honglong’ fruits; the temperatures were 0, 3, 5, and 10 ◦ C. Numerous studies have indicated that carambola fruits stored below 5 ◦ C exhibit CI, the severity of which increases with the storage time (Ali et al., 2004; Miller and McDonald, 1997; Wan and Lam, 1984; Warren et al., 2007). The CI symptoms on carambola fruits include dark brown concave spots (<1 mm) on the fruit peel surface, large brownish spots (1–2 mm), and rib-edge browning. Kader (2009) indicated that some carambola species stored at 0 ◦ C for 2 weeks or at 5 ◦ C for 6 weeks exhibited CI after being stored for 2 days at 20 ◦ C. In the present study, fruits exhibited CI at all four temperatures, with injury occurring earlier at lower storage temperatures. ‘Honglong’ fruits exhibited CI after storage at 10 ◦ C for 22–26 days (Fig. 6). Ali et al. (2004) observed CI in ‘B10’ fruits stored at 5 and 10 ◦ C; specifically, only 9% of the fruits stored for 25 days at 10 ◦ C exhibited injury, but all of the fruits stored for 40 days at 10 ◦ C exhibited injury. Pérez-Tello et al. (2001) investigated the CI to ‘Yau’ fruits stored at 2, 10, and 20 ◦ C and found those stored at 2 and 10 ◦ C exhibited CI; in addition, the onset of CI was related to peroxidase and phenylalanine ammonia-lyase activity. The influence of storage temperature on vegetable and fruit quality depends on their metabolic rate. Fruit chlorophyll degradation and increased enzyme activity promote color change in fruits (Amir-Shapira et al., 1987). In the present study, the hue value of the winter fruits stored at 5 ◦ C remained higher than 100◦ (Fig. 4). Lam and Wan (1987) indicated that the rate of color change depends on the storage temperature, and the color remains for fruits stored at 5 ◦ C after harvest. Ali et al. (2004) indicated that compared with modified atmosphere packaging, using a lower storage temperature was effective for delaying the onset of color change in ‘B10 fruits. In the present study, the summer fruits maintained their color when stored at 5 ◦ C. O’Hare (1993) indicated that carambola fruits could prevent rib scald when stored for 4 weeks at 10 ◦ C; in addition, carambola fruits could remain unchanged for 5 weeks at 0 and 4 ◦ C. O’Hare (1993) also indicated that at high temperatures, carambola fruits could turn yellow at the same time that chlorophyll degradation occurs. In the present study, the winter fruits retained their firmness when stored at 0 ◦ C after 28th day, and the summer fruits stored at 5 ◦ C generally exhibited high firmness (Fig. 5). Ali et al. (2004) indicated that storing carambola fruits at 5 ◦ C and 85% to 95% relative humidity effectively prevents water loss and promotes firmness. Compared with the quality of completely ripened carambola fruit, that at 70% and 80% maturity is superior (Paull and Chen, 2014). Storage at a low temperature can reduce the respiration rate and thermal decomposition rate and maintain the freshness and shelf life of products (Cheng and Shewfelt, 1988). In the present study, the storage life of the fruits stored at 5 ◦ C was significantly longer
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than the fruits stored at 10 ◦ C (Table 3). The shelf life of the winter fruits stored at 5 ◦ C was relatively long; that of the summer fruits stored at 3 and 5 ◦ C was also relatively long during the late-storage period (Table 3). Although carambola fruits are tropical, they can be stored at 4–5 ◦ C under 90% to 95% relative humidity for 21–35 days (Kader, 1999). According to Pauziah et al. (2009), carambola fruits at the advance maturity stage can be stored for 8 weeks at 8 ◦ C. In Taiwan, ‘Honglong’ fruits are produced throughout most of the year; the color and quality of summer fruits are superior to those of winter fruits; ‘Honglong’ fruits at 70% maturity are bright green-yellow, high in TSS, low in TA, and exhibit excellent quality that accepted by consumers; in addition, their storage life and cold resistance at 70% maturity are superior those at 60% maturity. A storage and transportation temperature of 5 ◦ C was found to be optimal for maintaining the food quality, storage life, and shelf life; storage temperatures of 0 and 3 ◦ C caused severe CI; a storage temperature of 10 ◦ C made the fruits rapidly turn yellow and become rotten. Therefore, we suggest that ‘Honglong’ fruits be harvested at 70% maturity and be stored at 5 ◦ C for commercial purposes. References Abbas, M.F., 1997. Jujube. In: Mitra, K.S. (Ed.), Post-harvest Physiology and Storage of Tropical and Subtropical Fruits. CAB International, Wallingford, pp. 405–415. Ali, Z.M., Chin, L.H., Marimuthu, M., Lazan, H., 2004. Low temperature storage and modified atmosphere packaging of carambola fruit and their effects on ripening related texture changes, wall modification and chilling injury symptoms. Postharvest Biol. Technol. 33, 181–192, http://dx.doi.org/10.1016/j. postharvbio.2004.02.007. Amir-Shapira, D., Goldschmidt, E.E., Altman, A., 1987. Chlorophyll catabolism in senescing plant tissues: in vivo breakdown intermediates suggest different degradative pathways for citrus fruit and parsley leaves. Proc. Natl. Acad. Sci. U. S. A. 84, 1901–1905, http://dx.doi.org/10.1073/pnas.84.7.1901. Ashok, R., Shoba, H., Chidanand, D.V., 2011. A study on shelf life extension of carambola fruits. Int. J. Sci. Eng. Res. 2, 1–5. Braman, K., Ahmad, S., Siddiqui, M.W., 2015. Factors affecting the quality of fruits and vegetables. In: Siddiqui, M.W. (Ed.), Postharvest Biology and Technology of Horticultural Crops. CRC Press, Boca Raton, FL, pp. 1–50. Campbell, C.W., 1989. Carambola production in the United States. Proc. Inter.—Am. Soc. Trop. Hort. 33, 47–54. Cantwell, M.I., 2002. Appendix: summary table of optimal handling condition for fresh produce. In: Kader, A.A. (Ed.), Postharvest Technology of Horticultural Crops. University of California, Richmond, CA, pp. 511–518. Cheng, T.S., Shewfelt, R.I., 1988. Effect of chilling exposure of tomatoes during subsequent ripening. J. Food Sci. 53, 1160–1162, http://dx.doi.org/10.1111/j. 1365-2621.1988. tb13552.x. Chin, L.H., Ali, Z.M., Lazan, H., 1999. Cell wall modifications, degrading enzymes and softening of carambola fruit during ripening. J. Exp. Bot. 50, 767–775, http://dx.doi.org/10.1093/jxb/50.335.767. Ding, P., Ahmad, S.H., Ghazali, H.M., 2007. Changes in selected quality characteristics of minimally processed carambola (Averrhoa carambola L.) when treated with ascorbic acid. J. Sci. Food Agric. 87, 702–709. Dodd, M.C., Bouwer, J.J., 2014. The supply value chain of fresh produce from field to home: refrigeration and other supporting technology. In: Florkowski, W.J., Prussia, S.E., Shewfelt, R.L., Brueckner, B. (Eds.), Postharvest Handling: A Systems Approach. Acadcmic Press, San Diego, CA, pp. 449–483. El-Anany, A.M., Hassan, G.F.A., Rehab Ali, F.M., 2009. Effects of edible coatings on the shelf-life and quality of Anna apple (Malus domestica Borkh) during cold storage. J. Food Technol. 7, 5–11. Kader, A.A., 1999. Fruit maturity ripening and quality relationships. Acta Hort. 485, 203–208, http://dx.doi.org/10.17660/ActaHortic.1999.485.27.
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