Studies on Relationship Between SO_2 Injury and Titratable Acidity，pH，Buffer Capacity in Grape Juice

：Titratable acidity and pH in ripe grapes juice are 0．5％～0．7％ and 3．7～3．8 respectively，a SO2-endurable variety has higher level of titratable acidity，pH and buffer capacity than a SO2-unendurable one． During senescence of grapes， there are falls of titratable acidity and buffer capacity． Superfluous SO2 induces a raise of titratable acidity and a more fall of buffer capacity， while appropriate SO2 keeps a relatively changeless level．