Removal of red blush and bitterness from white wine by partial hyperoxidation of juice from the pink-skinned koshu variety

Abstract

White wine which is produced using sulfited juice from koshu grapes, the most important cultivar native to Japan, sometimes has bitterness and/or astringency and a red blush. Blowing compressed air through unsulfited juice for a short period of time results in less bitterness and/or astringency and no red blush, thereby improving wine quality, whereas conventional hyperoxidation produces thin, watery wine with little colour and poor body. It was found that the bitterness and/or astringency of wine made from sulfited juice is due to oligomeric and polymeric tannins extracted from skin and perhaps seed of soft koshu grape berries during crushing, stemming, and pressing, whereas the red blush is probably due to excess caffeic acid derivatives, anthocyanins or anthocyanin–flavonoid complexes, and cyanidins produced from procyanidins. Partial hyperoxidation removed the phenols responsible for the bitterness and/or astringency and the red blush via enzymatic oxidation (uninhibited by SO₂), polymerisation, and insolubilisation.

Acknowledgements

The authors wish to express their gratitude to Professor Yoshifumi Amano of the University of Yamanashi for valuable discussions.