In order to improve qualities of wine from Koshu vines which was the traditional Japanese variety for white wines, virus free grapevine leafroll virus (GLRV) was performed by meristem tip culture. Some principal components of fruits from healthy and GLRV infected vines were compared at the different season, and wines produced from these vines were analyzed at subject to taste evaluations.
°Brix in fruits of healthy vines was 22. °Brix reading of the expressed juice from GLRV infected vines was 4 below that of healthy fruits.
Total acidity, malate and tartrate were significantly greater in fruits from GLRV infected vines than in fruits from healthy vines. Mainly malate in fruits from GLRV infected vines did not decreased from early October. The difference in pH was negligible. The concentration of total free amino acids in fruits from healthy vines was significantly higher than in GLRV infected vines at all stages of fruit development. Proline was also present at a higher level in healthy fruits compared to infected fruits during the ripening period. The level of proline in fruits from healthy vines was 1262mg/liter and in fruits from GLRV infected vines, 565mg/liter at harvest. Vines with GLRV was less fruitful than healthy vines.
The wine from healthy vines had higher levels of total nitrogen and proline than the wine from GLRV infected vines. However, there were no differences in aldehydes, higher alcohols, esters, and phenolic compounds, except for leuconoanthocyanin. Taste evaluation tests indicated that the wine from healthy vines was good acid-sugar balance and more full-bodied than wine from GLRV infected vines.
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