To evaluate th edifference in flavor between ‘Koshu’ and ‘Riesling’, the formation of C
6-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 SO
2 in the must remarkably depressed the formation of C
6-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 SO
2 concentration on the formation of C
6-compounds in the must were somewhat different between ‘Koshu’ and ‘Riesling’. In ‘Koshu’, almost no C
6-compounds except trans-2-hexenal, which was found at about 250μg/
l, were formed in the presence of 200 to 1, 000ppm SO
2. In ‘Riesling’, however, 1-hexanol and trans-2-hexenol were formed, though slightly, in the presence of 200 to 1, 000ppm SO
2 in addition to trans-2-hexenal.
4. Heat treatment of berries at 65°C for 10 to 15 minutes depressed completely the formation of C
6-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. C
6-compounds were formed in large amounts when crushed in distilled water, in less amounts in the presence of 200ppm SO
2 and in the least amounts in dichloromethane. In distilled water, ‘Riesling’ formed more C
6-compounds than ‘Koshu’ irrespective of the addition of SO
2. The amount of C
6-compounds in dichloromethane might be supposed to be the original content in fresh berries. Thus, in fresh berries, C
6-aldehydes were higher in ‘Koshu’ than ‘Riesling’, while, there was no difference in C
6-alcohols between two cultivars.
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