عنوان مقاله [English]
Harvest at inappropriate time is the most important factor in reducing the fruit quality, marketability, and postharvest life of kiwifruit. In this study, the effect of different harvest times on fruit quality, nutritional value, and organoleptic characteristics of two novel kiwifruits of yellow and red flesh was investigated. Fruits from promising genotypes were harvested at 130, 140, 150, 160, 170, and 180 days after full bloom (DAFB). The results showed that fruits harvested after 180 DAFB showed higher weight, length, diameter, dry matter, soluble solids content, and total soluble sugars. Meanwhile, titratable acidity was lower than fruits harvested earlier. The values of soluble solid content ranged from 6.80 to 11.66° brix in golden kiwifruit and from 6.90 to 13.70° brix in red flesh kiwifruit. With delayed harvest, total phenols, ascorbic acid content, DPPH and FRAP antioxidant capacity and hue angle in outer and inner pericarp decreased in both genotypes. Ascorbic acid content in the red-fleshed genotype decreased from 90.34 to 75.57 mg/100 g and in the golden genotype from 74.83 to 50.62 mg/100 g. Fruits from the red-fleshed genotype had the higher antioxidant capacity and nutritional value compared to the golden genotype. There was a positive significant correlation between ascorbic acid content and antioxidant capacity measured by DPPH (r=0.98) and FRAP (r=0.95) methods. In conclusion, novel golden and red flesh kiwifruit genotypes reached the minimum soluble solid content and hue angle for commercial harvest with favorable organoleptic properties only at 170 DAFB and the delay in harvest increased the organoleptic properties in both genotypes. However, the content of their antioxidant capacity was slightly lower compared to the early harvest.
Kiwifruit (Actinidia spp.) belongs to the deciduous perennial vines family Actinidiaceae, which mostly grows in warm-temperate climates in northern China. Determining maturity indices not only faciliates harvesting, storage, transport and marketing, but also guarantees sensory and nutritional quality and improves shelf-life. Currently there are no maturity indices available for kiwifruit, except for soluble solids content, which is not specific to different cultivars. The most common maturity indices for harvesting include total degree days, sugar content, starch test, chromaticity and days after full bloom (DAFB). Measuring sugar content is the main method that domestic growers use to determine harvest time, after which they harvest the fruit collectively. Relying solely on sugar content as a maturity index can result in mixed harvesting, which may affect fruit quality and storage life. Low temperatures in autumn halt kiwifruit maturity and is considered the main restricting factor regarding kiwifruit harvest time in the northern hemisphere. While, high enough autumnal temperatures support fruit growth and ripening in northern Iran.
Materials and Methods
Improper harvest time has a drastically negative effect on quality, marketability and storage life of kiwi fruit. In this study, the effect of different harvesting time on fruit quality, nutritional quality and organoleptic characteristics of two novel kiwifruit with golden and red flesh was investigated. Fruits from promising genotypes were harvested at 130, 140, 150, 160, 170 and 180 days after full bloom (DAFB). The experiment was carried out during the 2020 -2021 growing season in a commercial kiwifruit orchard located at Rasht (latitude 37◦ 11' N; longitude 49◦ 38' E; Guilan province, Iran) containing mature red and golden-fleshed Actinidia chinensis genotypes. Qualitative characteristics such as weight, length, diameter, L/D, soluble solids content (SSC), total soluble sugars (TSS), titratable acidity (TA), pH, tissue firmness, ascorbic acid content (AAC), total polyphenol content (TPC) and total antioxidant capacity (DPPH and FRAP) were measured for fruits from both genotypes. Data analysis for this experiment was performed using SAS software version 9.4. Treatment average comparison was carried out using Tukey's test (1% significance level). The 2022 edition of Origin Pro software was used to draw all graphs.
The results revealed that fruits harvested after 180 DAFB showed higher weight, length, diameter, dry matter, soluble solids content and total soluble sugars. Meanwhile, titratable acidity was lower than fruits harvested earlier. Soluble solid content in golden and red flesh kiwifruit ranged from 6.80 to 11.66 and 6.90 to 13.70° brix, respectively. Delay in harvesting in both genotypes caused considerable decrease in total phenols, ascorbic acid content, DPPH and FRAP antioxidant capacity and hue angle in the outer and inner pericarp. Delayed harvest decreased the outer pericarp hue angle in both genotypes. In the final harvest of both red and golden-fleshed genotypes (180 DAFB), the lowest outer pericarp hue angle was observed at 106.72 and 101.71 degrees, respectively. The lowest inner pericarp hue angle for red and golden-fleshed genotypes was measured at 180 DAFB (68.31 and 101.80 degrees, respectively). Ascorbic acid content in the red-fleshed genotype decreased from 90.34 to 75.57 mg/100 g and in the golden genotype from 74.83 to 50.62 mg/100 g.
Ascorbic acid content showed a decreasing trend as the fruit ripened and remained at a constant level during the full ripening stage. In overripe fruits, along with fruit tissue degradation, the ascorbic acid content also declines. Fruits from the red-flesh genotype had higher antioxidant capacity and nutritional value compared to the golden genotype. There was a significant positive correlation between ascorbic acid content and antioxidant capacity measured by DPPH (r=0.98) and FRAP (r=0.95) methods. Both genotypes reached the minimum content of soluble solids content for commercial harvesting at 170 DAFB and the delay in harvesting increased organoleptic properties in both genotypes.