Comparison of Composition of Koshu White Wines Fermented in Oak Barrels and Plastic Tanks

¹ Institute of Enology and Viticulture, Yamanashi University, Kofu, Yamanashi 400, Japan
² University of California, Davis, CA 95616-8749.

Koshu musts (six-experiment series) from grapes harvested over four years (1988 to 1991) were fermented at 15°C under four different conditions: (A) fermentation entirely in a small plastic tank; (B) fermentation entirely in a small oak barrel; (C) fermentation to about 6% alcohol in a plastic tank followed by fermentation to dryness (about 12%) in an oak barrel; and (D) fermentation entirely in a tank, followed by storage in an oak barrel for the same number of days as the tank fermentation. The production rate of ethanol and duration of complete fermentation to dryness were slowest and longest under condition B, in spite of the fact that the fermentation temperature was slightly higher (about 1°C) in a barrel than in a tank. There was little difference in the production rate of ethanol, the fermentation temperature, and the duration of fermentation to dryness among the fermentations under conditions A, C, and D. There were appreciable differences in non-flavonoid phenol, total amino acids, proline, higher alcohols, and esters among the wines made under the four conditions. Storage in a barrel for 13 days of the wines fermented completely in a tank increased the non-flavonoid phenols, but did not influence the composition of higher alcohols and esters. The results suggest that the difference in the composition of proline, higher alcohols, and esters was due to the degree of turbidity (suspended materials) of the fermenting must and the extent of aeration, which differed with the containers used.

Key words: barrel aging, oak, tank aging, white wine

Submitted on February 5, 1993