Field of Science

Hurricane Chemistry: Renovating Butter

Hurricane Sandy left us without power for several days and while a basement chest freezer remained solidly frozen, thermal equilbrium was unfortunately reached by our refrigerator and kitchen, at roughly 55oF.  Saturday morning found us rooting through the refrigerator, deciding what had to be chucked (milk) and what didn't (ketchup).  Butter?  In this cool weather, it could stay, it would be unlikely to have turned rancid.

But coincidently, while breezing through a depression era Chemcraft chemistry set instruction book, I encountered directions for "renovating" rancid butter.  Around the same time that margarine made its debut, so did process butter, butter that had been treated to remove the objectionable materials.  As near as I can tell, it's an extraction process, presumably the rancid materials (such as butyric acid) dissolve in the cream and the remaining materials can be reworked into a solid mass.

Laws remain on the books in many places forbidding the sale of process butter without making clear to the consumer what is being purchased.  In the early part of the 20th century this was widespread enough for the US Department of Agriculture to print a booklet which "enable[s] any housekeeper, with only the usual facilities of the kitchen, to distinguish in the great majority of cases between genuine butter, renovated butter, and oleomargarine."

Next time the power goes out, I'll know how to "renovate" my butter, as long as I don't intend to sell it!


  1. It is fascinating to imagine un-ranciding butter, that what seemed a permanent state is not.

  2. Very cold. I think the butter can be exactly frozen at that temperature.

    thank you.


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