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airtight lid = sour stock?

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airtight lid = sour stock?

limesatpirate | May 22, 2010 08:35 PM

Julia Child recommends to never cover the kettle airtight or else the stock will
sour.

Does this make sense to anyone? Because I have a crockpot with a rubber seal to
keep in heat.

5 million Frenchmen can't be wrong!

A cook told me that professional cooks always leave stockpots uncovered or only partially covered.

Is this true? If so I'd like to know why.

Here's my guess FWIW:

An airtight seal with added heat can induce anaerobic fermentation, a chemical process that releases CO2, ammonia, and organic acids. Perhaps this chemical reaction produces the "sour" Julia Child is referring to?

I got this idea from :
http://en.wikipedia.org/wiki/Anaerobi...
and here
http://en.wikipedia.org/wiki/Biogas

thx for any help!

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