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"Why did my bottle of sherry become slushy?"

Dear Anne and Sue,

I left a bottle of sherry in the freezer by mistake. When I took it out it wasn’t frozen, but when I poured it into a glass (at room temperature) it formed perfectly hexagonal ice crystals, and the whole glass turned into a sort of sherry slush puppy.

Do you have an explanation for this? I’d be interested to know what your thoughts are.



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Dear Belinda,

A “sherry slush puppy”? Sounds intriguing! Here’s what probably happened:

The reason the sherry didn’t freeze is because of the amount of alcohol it contains; alcohol lowers the freezing temperature of liquids. Most table wines freeze at about 15ºF (-10°C). However, because sherry is a fortified wine, meaning it has a higher alcohol content, it can stand even lower temperatures than table wines without freezing completely.
Tartaric acid is the most plentiful acid found in grapes. Its presence in wine contributes acidity and flavor and also helps maintain wine’s color. Freezing temperatures cause the tartaric acid in wines to precipitate in the form of crystals. Depending on the degree of “slushiness,” there were likely ice crystals in your sherry, too. (Incidentally, precipitated tartrate crystals are a byproduct of the wine industry. After being precipitated out in the wine-making process, they become cream of tartar, an acid used in baking.)

Wines with lower alcohol contents than sherry can actually freeze. When this happens, ice crystals form. However, because ice takes up more space than the same amount of water, the ice usually forces the cork out of the bottle, or even breaks the glass as it expands and exerts pressure on the wine bottle.

It’s now trendy to serve sherry over ice with a slice of orange. This would save chilling the sherry, so you can avoid the attendant risk of it freezing (or “slushing”!).

Anne & Sue


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