Evaluation of Fruit Characteristics of Shima sarunashi (Actinidia rufa) Indigenous to Warm Regions in Japan

Abstract

The fruit characteristics of Shima sarunashi (Actinidia rufa (Siebold & Zucc.) Planch. ex Miq.), indigenous to the warm regions in Japan were determined. Two typical collections were investigated to evaluate fruit characters throughout growth. Starch accumulated gradually from 120 days after full bloom (DAFB), and peaked at 160 DAFB. Along with the reduction of the starch content, the sugar content increased at 180 DAFB. Major sugar components of A. rufa fruit were glucose, fructose, and sucrose. In the early stage of fruit development, quinic acid was predominant, and then the content decreased gradually until 160 DAFB, while the content of citric acid gradually increased after 60 DAFB and that of malic acid increased slightly. A trace amount of soluble oxalate was detected throughout the fruit development period. Ascorbic acid content increased in the early to mid-stages of fruit development. Considering the change in quality, the maturation period of A. rufa fruit was estimated to be 180 DAFB. From the evaluation of mature fruit among 11 local collections, fruit shape varied, being round, ovoid, cylindroidal, and truncate. Fruit weight ranged from 7.4 to 18.6 g. Fruit skin was glabrous and the surface color varied from reddish-brown to brown. Flesh color was basically green or dark green. Exceptionally, in one collection, the flesh was reddish around the core. Soluble solid content of ripened fruit juice ranged from 6.2 to 17.4%. Sugar content varied from 2.0 to 15.6 g/100 g FW. Myo-inositol content ranged from 6.0 to 132.1 mg/100 g FW. Major organic acids were quinic, citric, and malic acid, and quinic acid was predominant. Total acid content ranged from 1.5 to 3.0 g/100 g FW. Total ascorbic acid content ranged from 6.8 to 45.8 mg/100 g FW. In all collections, protease activity in the juice was very low.