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Ron Wilson — Hamilton, Ontario asks,
My father-in-law makes wine from grapes, de-stemmed and put in pails. He does the usual vatting and filtering and transferring demi-johns, etc. Once the wine is ready, we put it in gallon (3.8 L) bottles and store it in our basement cold cellar until we need some, at which time we transfer it into 750 ml bottles. When we open the gallon (3.8 L) jugs, there is sometimes (not always) a topping of what appears to be mold or something. It doesn’t smell or anything. The father-in-law says to carefully remove it, but often some bits remain, which we filter with a strainer when bottling. The wine always tastes fine, but I wonder if it is okay to drink?