An essential source of protein, vitamins and essential minerals, milk also contains a variety of bacteria that pose no threat to your health. The souring process introduces new bacteria to milk, transforming the texture, odor and taste. While this change may be appealing to some, if you are not accustomed to the process, you may wonder if sour milk will hurt you.
What is Sour Milk?
Sour milk, also known as cultured milk or buttermilk, has a sour or tart taste, achieved by adding an acid to the milk, which causes it to curdle. Lemon juice or vinegar are the most common acids used in home fermentation. Industrial bacterial fermentation is another type of fermentation that uses bacteria to sour milk. The University of California, Davis Campus explains that lactic acid bacteria are crucial to the industrial bacterial fermentation process. Adding Streptococcus lactis during bacterial fermentation gives the sour milk a creamy texture. Streptococcus lactis poses no health risks in fermented milk products.
Misconceptions
Sour milk is commonly confused with spoiled milk. In reality, the two are quite different. When refrigerated milk passes its expiration date or spoils, psychrotrophic bacteria begin to grow in the container, altering taste, according to Penn State College of Agricultural Sciences Cooperative Extension. Psychrotrophic bacteria are diarrheal bacteria, which may give you a bad case of diarrhea if ingested. Milk left unrefrigerated for several hours develops bacteria that can cause serious illness, which can be fatal to the elderly, babies and pregnant women.
Good Bacteria
Sour milk and other products that are the result of fermentation contain live bacteria that are helpful, not harmful. Live bacteria, or probiotics, have a long history that dates back to ancient times. The University of Nebraska, Lincoln explains that probiotics strengthen the immune system, reduce the risk of cancer, allergies, diarrhea, stomach ulcers, kidney stones and irritable bowel syndrome. If you are lactose intolerant, consuming sour milk products that contain probiotics will make digestion easier, because the live cultures break up the lactose sugars before they enter your intestines.
Expiration
Despite the fact that it is alive, sour milk does have an expiration date. Sour milk will begin to spoil if neglected on the counter for several hours. Storing sour milk in an airtight container in the refrigerator will extend its usability. North Dakota State University suggests discarding refrigerated sour milk one to two weeks after preparation. To avoid exposure to harmful bacteria, discard store-bought sour milk in accordance with the expiration date stamped on the packaging label.
References
- University of California, Davis Campus: Dairy Bacteriology: An Introduction to Bacteria
- Penn State College of Agricultural Sciences Cooperative Extension; Sour Milk; Bob Roberts
- North Carolina State University Cooperative Extension; Protecting the Safety of Milk; J.E. Rushing; June 2011
- University of Nebraska, Lincoln; A Healthy Lifestyle With Probiotics and Prebiotics; Julie A. Albrecht; July 2008
- North Dakota State University; Food Storage Guide; Julie Garden-Robinson; August 1998
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