The formation process of tartar in purees produced from five varieties of grape, 'Delaware', 'Neomuscat', 'Kyoho', 'Koshu' and 'Muscat Bailley A' (MBA), was investigated during storage at 5℃ and 20℃. The tartar was measured by isolating water insoluble tartar (WIT) and alcohol insoluble tartar (AIT) from the purees. Tartar was formed in all samples, but with large differences in amount, depending on variety. 'Koshu' provided the greatest amounts, while MBA provided the least. The amount and rate of formation of tartar were higher at 5℃ than at 20℃. The amount and rate at 20℃ were lower than those at 5℃, remarkably in 'Delaware' and 'MBA'. The measurement of WIT and AIT was effective in prediction of tartar formation, and could be used as an index of tartar stability. The crystal structure observed by stereomicroscope was quite clear, indicating that crystallization occurred quickly.
