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added note about adding fresh yeast when fruiting
When using whole fruit, it is typical for the fruit to be carried to and held at the top of the fermenter by the carbonation. Some producers have voiced concern over the fruit sitting for prolonged periods of time in contact with air and prefer to push the fruit cap down periodically (and to ferment in such a vessel as to allow this)<ref name='Jester King on the Sour Hour pt. 1'/> (~40 minutes in). If you are fermenting in carboys and feel that you are getting acetic character from the fruit cap being in contact with air you can swirl the carboy periodically. Note that many who have used whole fruit have not noticed any problem with a fruit cap being in contact with air, so you may or may not find that this is a concern for you<ref>[https://www.facebook.com/groups/MilkTheFunk/permalink/1170422922985920/ MTF facebook thread about fruit caps]</ref>.
Adding yeast when adding fruit is an option, but not necessary, even for really old sour beers. There should still be some living ''Brettanomyces'' in the beer. Yeast could be added optionally, which might help reduce the effects of added oxygen or speed up the re-fermentation process, but it is generally not necessary.
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