ブドウ‘甲州’における味なし果と健全果の経時的成分変化について

Abstract

“Ajinashi” disease of Koshu grapevine (Vitis vinifera Linn. cv. Koshu) was first recognized in Yamanashi Prefecture in 1968.The disease shows no visible symptoms on the growth of vines and the yield of berries. But the berries are unsuitable not only for the table grape but also for the wine grape owing to a marked decline in sugar content, from which comes the name of this disease.In this paper, seasonal changes in diameter and weight of the berries, and in reducing sugar, glucose, fructose, titratable acid, tartaric acid and malic acid in the juice were investigated in comparison of the normal and “Ajinashi berries”. The results were summarized as follows:1. The growth curve of the “Ajinashi” berry was almost the same as that of the normal berry, although the size and weight of the “Ajinashi” berry were somewhat greater than those of the normal berry.2. The “Ajinashi” berry accumulated sugars as much as the normal one unti lthe 80th day after anthesis. At the harvest time, however, it had no more than 12% of soluble solids, 11.3% of reducing sugar, 5.2% of glucose and 5.7% of fructose in contrast to 19% of soluble solids, 18.0% of reducing sugar, 8.4% of glucose and 9.4% of fructose in the normal berry.3. The “Ajinashi” and normal berries accumulated the highest titratable acid on the 60th day after anthesis, when they contained malic acid more than tartaric acid. After that, however, malic acid was consumed more rapidly than tartaric acid. As a result, titratable, malic and tartaric acid contents of the “Ajinashi” berry were 0.95, 0.40 and 0.70g/100ml and those of the normal berry were 0.86, 0.30 and 0.80g/100ml, respectively, at the harvest time. The ratios of the combined acid to the total acid were 17.4% in the Ajinashi berry and 24.6% in the normal berry.