1981 Volume 50 Issue 3 Pages 393-399
To evaluate th edifference in flavor between ‘Koshu’ and ‘Riesling’, the formation of C6-compounds in grape berries of different maturity and in the musts obtained by crushing berries under various conditions was investigated.
1. In ‘Riesling’ berries, the amouts of trans-2-hexenal and 1-hexanal reached the maximum value when sugar content reached the maximum with maturity, and decreased thereafter. While, 1-hexanol and trans-2-hexenol which were found only in small amounts, increased with time throughout ripening.
2. In ‘Riesling’ must, trans-2-hexenal and 1-hexanal increased rapidly until 60 minutes after crushing and then decreased, while, 1-hexanol and trans-2-hexenol showed a steady increase with time, although their amounts were small. The pressence of 100ppm SO2 in the must remarkably depressed the formation of C6-compounds, at least, during 120 minutes after crushing except trans-2-hexenal, which was less depressed in its formation and increased with time.
3. The effects of SO2 concentration on the formation of C6-compounds in the must were somewhat different between ‘Koshu’ and ‘Riesling’. In ‘Koshu’, almost no C6-compounds except trans-2-hexenal, which was found at about 250μg/l, were formed in the presence of 200 to 1, 000ppm SO2. In ‘Riesling’, however, 1-hexanol and trans-2-hexenol were formed, though slightly, in the presence of 200 to 1, 000ppm SO2 in addition to trans-2-hexenal.
4. Heat treatment of berries at 65°C for 10 to 15 minutes depressed completely the formation of C6-compounds in both cultivars, except that in ‘Riesling’, little 1-hexanol and trans-2-hexenol were formed even by the treatment over 65°C for 15 minutes.
5. The berries were crushed in different solvents out of contact with air. C6-compounds were formed in large amounts when crushed in distilled water, in less amounts in the presence of 200ppm SO2 and in the least amounts in dichloromethane. In distilled water, ‘Riesling’ formed more C6-compounds than ‘Koshu’ irrespective of the addition of SO2. The amount of C6-compounds in dichloromethane might be supposed to be the original content in fresh berries. Thus, in fresh berries, C6-aldehydes were higher in ‘Koshu’ than ‘Riesling’, while, there was no difference in C6-alcohols between two cultivars.