Effect of long-term cold storage on physicochemical attributes and bioactive components of kiwi fruit cultivars

Abstract

Various kiwi fruit cultivars, bred in Korea, were kept in cold storage for 8-24 weeks for possible increase of their quality. Firmness significantly decreased at initial time in all cultivars. The rate of softening was the slowest in "Hayward", followed by "Hort 16A", "Haenam", "Daheung", "Bidan", "Hwamei", and "SKK 12". Sensory value increased with decreasing of firmness. Soluble solids content increased with storage time while acidity gradually decreased. Reducing sugar content significantly increased at early stage of storage with decreasing of starch content. There was no difference of these indices among cultivars. Respiration rate increased with time and then decreased during cold storage. Peaks time was different between cultivars, therefore we represented trend of respiration changes in all cultivars. All kiwi fruit cultivars showed climacteric patterns in respiration. The rate of softening was closely related to the degree and peak time of ethylene production. The highest shelf life was in "Hayward" and "Hort 16 A" (24 weeks) and the lowest in "SKK-12" (8 weeks). All investigated cultivars bred in Korea showed much lower shelf life than "Hayward" and "Hort 16 A". Radical scavenging assays and chemometrical processing were used for the determination of bioactive kiwi fruits compounds. Polyphenols in water extracts were the highest in "SKK-12" and the lowest in "Hayward" [16.34 ± 1.11 and 5.30 ± 0.45 mg gallic acid equivalents (GAE)/g dry weight (DW)]. The values of β-carotene activities (27.61 ± 2.44% and 8.33 ± 0.74%) and Ferric-reducing/antioxidant power [(FRAP, Trolox equivalent (TE)/g DW) 24.55 ± 2.01 and 7.12 ± 0.41] were the highest in "SKK-12". The lowest results were estimated in "Hayward". All kiwi fruit cultivars showed a high level of correlation between the contents of phenolic compounds (polyphenols, tannins, and flavonoids) and their antioxidant values. We presented for the first time the results of shelf life of new cultivars bred in Korea and their comparison with the widely studied ones, such as "Hayward" and "Hort 16A". Cold storage extended shelf life in kiwi fruit without any chilling injury or color change. According to the antioxidant properties of different cultivars, the highest was in "SKK-12" with the lowest shelf life and the lowest was in "Hayward" with the highest shelf life.