Grapes

Asked September 17, 2019, 6:01 PM EDT

I have grapes in my yard that are supposed to be Concord. The grapes are purple. When making juice or jelly, the juice is red, not purple. Is this right?

Livingston County Michigan grapes

1 Response

The pigments of anthocyanin are sensitive to pH. In acid solutions (pH 4) they are red, as the pH rises (5-6) they become blue, in neutral solutions (pH 7) they are purple and then fade to green and yellow as the solution becomes alkaline.
Your juice is fine. You may be harvesting the grapes too early when the acid levels are high and the sugar levels are low.You may want to wait to harvest your grapes until the acid to sugar ratio declines as the berries ripen.
Concord harvest in SW Michigan usually starts around October 1 and the sugar is about 15 to 16 %