Abstract: 【Objective】 Actinidia chinensis var. chinensis and A. chinensis var. deliciosa are the main types of commercially cultivated kiwifruit at present, the inconvenience of peeling and eating both hinder consumers' choice of kiwifruit. Some varieties of kiwifruit, such as A. eriantha generally has the characteristics of easy peeling, however, there is no comprehensive and objective evaluation system for the description of the peeling traits of diffrent kiwifruit varieties. In this study, we compared the changes of fruit peeling traits of different kiwifruit varieties at soft ripening stage and established a comprehensive evaluation system of kiwi-fruit peeling traits to objectively reflect the difference of fruit peeling difficulty among different kiwifuit varieties, which will lay a theoretical foundation for further research on the physiology and molecular mechanism of kiwi-fruit peeling. 【Methods】 Twenty-five kiwifruit varieties were used as materials, including 16 A. chinensis var. Chinensis varieties, 4 A. chinensis var. Deliciosa varieties, and 5 A. eriantha varieties. The "peeling number", "peeling degree" and "peeling force" of each kiwifruit variety were tested respectively. The number of peeling refers to the number of skins removed from the whole fruit by manual tearing from the stylar end to the stalk end. Peeling degree was evaluated by assigning scores, which were divided into 5 grades according to peel and pulp peel degree (unable to peel at all, more difficult to peel, difficult to peel, easier to peel, easy to peel). Combined with the kiwifruit stripper based on the mechanical measuring device, the peeling force of each kiwifruit was determined by measuring the force in four directions of the fruit and the average value was selected as the peeling force. Then the evaluation system of kiwifruit peeling traits was established by synthesizing the three indexes, and the differences of peeling traits among different kiwifruit varieties were compared. 【Results】 According to the two indexes of peel number and peel degree, it was obvious that the peel number of A. eriantha was significantly less than A. chinensis var. chinensis and A. chinensis var. Deliciosa, and the peel degree evaluation grade was significantly higher than the two varieties, indicating that A. eriantha is easier to peel and has better peeling property than the other two kiwifruit varieties. However, according to the peeling force, the peeling force of A. eriantha is not the smallest, and the peeling power of A. chinensis var. chinensis and A. chinensis var. Deliciosa is even lower than that of A. eriantha. Therefore, by comprehensively comparing the fruit peeling number, peeling degree and peeling force of different varieties of kiwifruit, three indexes were obtained: Among the 16 varieties of A. chinensis with the same fruit size, Jinfeng (金丰)had less peeling times (18 times) than other varieties, the highest peeling degree was 3-4 points, and the pulp damage degree was lower, followed by Jinfeng(金奉), in the case of little difference in peeling number and peeling degree with other varieties, the average peeling force required is 0.42 N, which is the smallest. Among the 4 varieties of A. chinensis var. deliciosa with the same fruit size, Miliang 1 had little difference in peel number and peel degree compared with other varieties, but the average peeling force required is only 0.38 N, the peel was easier to peel, and the pulp was less damaged, although the number of Guichang peeling 20 times is the least, but the required peeling force is 1.2 N, the peel is also more difficult to peel. Among the 5 varieties of A. eriantha with the same fruit size, Ganlv 1 has at least 7 peeling times compared to the others, and the highest peeling degree is 7-8, and Ganlv 6 has the peeling degree was 5-6 points, the highest peeling number(13 times) and is relatively difficult to peel compared to the others. In summary, there are great differences in the peeling traits of different kiwifruit varieties. Among the 25 kiwifruit varieties, Ganlv 1 has the lowest peeling number, the highest peeling degree, and the lower peeling force, second only to the lowest Jinfeng and Milang 1, and it is the easiest to peel according to the evaluation of three indexes. The peeling number of Donghong and Hongshi 2 is as high as 49 times and 52 times, the peeling degree grade is 0, the average peeling force required is 1.68 N and 1.59 N, significantly higher than other kiwifruit varieties, so both are not easy to peel. 【Conclusion】 The fruit peeling characters of different kiwifruit species were different. At the same time, different varieties of the same kind of kiwifruit peeling characters also have great differences.By comprehensively comparing the fruit peeling number, peeling degree and peeling force of each varieties of kiwifruit, among the 25 kiwifruit varieties, Ganlv 1 has the lowest peeling number, the highest peeling degree evaluation grade, and the smallest peeling force, so it is the easiest to peel.
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