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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.
Regards,
Belinda
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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.
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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”!).
Cheers,
Anne & Sue
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