Most buttermilk, however, that is commercially available in the United States is actually skim or low-fat milk that has been heated to concentrate its proteins and create a thicker texture, then fermented with cultures until the milk gels slightly. The liquid is then cooled to stop the fermentation and gently agitated to break the curd into a smooth liquid. True buttermilk is more flavorful, less acidic, and more bioactively complex than its commercial counterpart. It is also, however, far more perishable and prone to off flavors, making it more challenging to bring to market.
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