Document Type : Research Paper
Authors
1 citrus and subtropical fruits research center
2 Citrus and Subtropical Fruits Research Center
3 .
Abstract
Introduction: It is important to attend the physical and biochemical characteristics of the fruit, especially in newly introduced cultivars that may be unknown to the consumer. Nutritive compounds in fruit are usually influenced by variety, rootstock and post-harvest conditions. In this article, the results related to the evaluation of the fruit quality of three varieties of oranges on two rootstocks have been examined at harvest time and during storage.
Materials and methods: Fruit of Thomson Novel, Fukumoto, and Navelate oranges on two rootstocks including Swingle Citrumelo and Citrange C-35 were harvested when TSS/TA reached about 6.5-7. Fruits were evaluated at the harvest time and then stored in cool storage (5oC, RH=85%) for 60 days. The fruit quality were checked on the 30th and 60th days of storage for two years. Characteristics evaluation were including fruit lenght, width, thickness; arithmetic, geometric, equivalent and harmonic means; fruit aspect ratio, sphericity, surface area, true volume, apparent volume, volume error, density, weight, weight loss, peel thickness, juice percentage, peel color indices (L*, a*, b*, hue angle, chroma and CCI), total soluble solid (TSS), titratable acidity (TA), technological index (TI), total phenol, ascorbic acid, antioxidant capacity and organoleptic evaluation.
Results: The fruit of Navelate orange on Citrumelo rootstock and Fukumoto orange on C-35 rootstock had smaller physical characteristics than Thomson Novel. In all treatments, the shape of the fruit was balanced and without elongation or indentation. The fruit of Navelate on Citrumelo (aspect ratio: 96.96) was slightly elongated. Navelate variety on C-35 produced larger and heavier fruit similarly Thomson fruit. The volume error in Fukumoto and Navelate varieties and on both rootstocks was less than the control. At the time of harvest, the fruit of the Fukumoto had a thicker peel (more than 4 mm) on both rootstocks than the other cultivars. The amount of juice percentage was not significantly different than control at harvest time, but at the end of storage, the fruit of Navelate on the C-35 had the lowest (35.73%) of juice percentage. Fukumoto and Navelate fruits on both rootstocks had higher TI index than Thomson at harvest time. The TSS at harvest time was the lowest (9.22 and 9.78 respectively) only in the fruits of Thomson and Navelate on Citrumelo rootstock. Navelate and Thomson fruits had higher TA on C-35 rootstock. In all treatments, the amount of TA decreased during storage. Fukumoto fruit on C-35 had the highest TSS/TA ratio, which was preserved during storage. The fruit of Navelate had a lower TSS/TA level at the harvest time on both rootstocks (7.12 and 7.5). At the time of harvest, the average ascorbic acid in all three cultivars on C-35 rootstock was higher than the same cultivars on Citrumelo rootstock. The value of a*, hue angle, and CCI of the skin of Navelate orange with a negative value were different from the other cultivars on Citrumelo and C-35 rootstocks (-1.12 and -0.61 respectively). The antioxidant capacity of Fukumoto fruit was 43.99% on Citrumelo and 62.12% on C-35 rootstock at the harvest time. The amount of antioxidant capacity and total phenol increased during storage. The organoleptic evaluation showed that the Fukumoto as Thomson, scored better in relations to peel and pulp appearance, sourness, aroma and taste than the fruit of the same cultivars on the C-35 rootstock. Navelate fruit produced higher score in terms of taste and sweetness (7) on Citrumelo rootstock than C-35 (6) rootstock.
Conclusion: Based on the TSS/TA ratio, it was determined that Fukumoto and Navelate oranges are early and late ripening respectively. Citrumelo rootstock increased late ripening in Navelate fruit and contrary C-35 rootstock increased early ripening in Fukumoto fruit. According to the a* and CCI indices, the Navelate fruits did not have suitable coloring at the time of harvest, and Citrumelo rootstock delayed the color change of the fruit skin. In general, the organoleptic characteristics of the fruit on C-35 were better than Citrumelo. Finally, it seems that the combination of Navelate/C-35 is more suitable than Navelate/Citrumelo. Fukumoto/C-35 combination is suitable for having early ripening fruit.
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