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Metatartaric Acid In Wine Kit

TroubleShooting

Rich Weaver — Casper, Wyoming asks,
Q

I am making one of the ultra premium wine kits, an Australian Shiraz. The instructions say to add the metatartaric acid package after racking on day 42 or 56. What is the purpose of adding the metatartaric acid on day 42 or 56 rather than adding it right after the Kieselsol and Chitosan addition on day 28 (approximately)?

A
Your question about metatartaric acid is a good one and one that brings to mind similar confusion and questions many of us have when faced with a litany of fining agents (and specific directions about how and when to use them). It sometimes seems like we can wing it, skip or combine steps or eliminate some of those packets and vials altogether. As a longtime reader you know that I’m not a big fan of adding things to wine willy-nilly. However, in the realm of kits, those professionals that sell them put them in the kits, with specific instructions, for a reason. In the case of metatartaric acid, its purpose is to help your Shiraz look its best in the bottle. Metatartaric acid is an esterified tartaric acid, which helps prevent the formation of potassium bitartrate crystals in finished wine. These crystals, sometimes called “wine diamonds,” fall out of solution as a wine ages and, especially in white wines and especially under cold storage conditions, can cause unsightly crystalline deposits in the bottom of wine bottles. Some commercial wineries have
Response by Alison Crowe.