What is buttermilk?

I am so sorry, loyal readers, for the delayed post. After flipping the calendar over to December, my world (like yours, no doubt) has become increasingly busy! (And my to-do list is charging me faster than my husband to freshly baked Christmas treats.) But, you didn’t think I’d leave you hanging, did you?

A few weeks ago someone asked me “What is buttermilk?” It was a good question. If you Googled the word you’d find a few quick blurbs describing buttermilk to be the liquid left after cream is churned into butter. But, since we might’ve guessed as much from the name alone, those blurbs leave you with a sour taste in your mouth and a curiosity thirsting for more. You’re wondering why buttermilk tastes more sour and pours thicker than milk. And you’re wondering why buttermilk is requested in a diverse range of recipes. Am I right? Thirst not, friends.

Okay, so traditionally speaking, buttermilk is the milky liquid drained after cream is churned into butter – and years ago that liquid was allowed to ferment naturally. However, commercially cultured buttermilk is produced under controlled, regulated processes. Like several other dairy products (cottage cheese, sour cream, and yogurt, to name a few), buttermilk is produced using a starter culture which facilitates fermentation and coagulation, yielding products with functional culinary attributes we’ve grown to rely upon.

For buttermilk, low-fat/skim milk is inoculated with a lactic acid starter culture, which converts lactose in the milk into lactic acid. (The starter culture also usually contains a Leuconostoc bacteria which is responsible for the characteristic tangy flavor). The inoculated milk is held until the targeted pH is reached and curdling occurs. Later, the milk curds are broken up through agitation and a thick, cultured buttermilk results. It’s the coagulation that makes cultured buttermilk more viscous than milk.

A Food Science tid-bite: Buttermilk is found in an array of recipes, functioning as a leavener, a tenderizer, a thick tangy flavor driver, and more. In baked goods, the lactic acid in buttermilk reacts with baking soda, giving rise to yummy leavened products – mmm…buttermilk biscuits, anyone? (Note: for detail, see baking soda vs baking powder post.) If soaked pre-cook, buttermilk can also be an effective tenderizer for meat. And, buttermilk mashed potatoes are only one example of the lovely tart flavor imparted by the versatile ingredient.

Source: Potter & Hochkiss. Food Science Fifth Edition. Aspen Publishers, Inc, 1998.

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