Comparison of Sugar Compositions and Quality Parameters during Berry Ripening between Grape Cultivars

Berry quality, coloration and sugar accumulation pattern were examined in 6 varieties of grape (Vitis labruscana B.) during ripening after verasion. Considerable drops of berry firmness (＜10 N) and titratable acidity (＜0.5%) were found at ripening stage, while the content of soluble solids was significantly increased along with the ripening process. Total levels of anthocyanin content among the cultivars were different, the concentration of anthocyanin sharply increased coinciding with the sugar accumulation in berries showing high correlation (r=0.956, P＜0.01) with maturity index (brix/acid) regardless of cultivars. L value of berry skin decreased after veraison. Correlations between color index for red grape (CIRG) and sugar/acid ratio were found in cultivars including ‘Campbell Early’ (r=0.802, P＜0.05), ‘Kyoho’ (r=0.853, P＜0.01), and ‘Heukguseul’ (r=0.832, P＜0.05). Sugar analysis of extractable juice by HPLC revealed that cultivars such as ‘Delaware’, ‘Campbell Early’, ‘Kyoho’, ‘Heukguseul’, and ‘MBA’ belonged to reducing sugar accumulating group at maturity and ‘Sheridan’ showed sucrose accumulation one. The rapid accumulation of glucose at ripening in former cultivars resulted in the increase of glucose/fructose ratio. These characteristic pattern of sugar accumulation may have a potential for the development as objective ripening index.