Here is a goal: how to get rid of foam when cooking jam

Which way makes more sense to accomplish this goal?

Select from:
(A). add a small pat of sour cream when cooking fruit for jams and jellies, you won't have any foam to skim off the top.;
(B). add a small pat of butter when cooking fruit for jams and jellies, you won't have any foam to skim off the top.;
(B).