Why Are Live Cultures Removed From Yogurt?

Commercially processed yogurt usually advertises the presence of active live cultures.

All yogurt is made by adding specific types of active live bacteria to milk. Many yogurt companies advertise the presence of the active cultures and their digestive health benefits, but some manufacturers remove the live cultures to create other product advantages.

Process

Homemade yogurt should be stored in the refrigerator.

To make yogurt, active live bacteria cultures are added to heated milk. These bacteria feed on the sugars in the milk, causing a buildup of lactic acid. This causes the proteins in the milk to coagulate and create solids that form into yogurt. The yogurt is then cooled to keep the bacteria from growing further.

Flavor

If bacteria growth is not halted, the lactic acid buildup continues and the taste and quality of the yogurt is significantly altered. According to Brian A. Nummer, Ph.D., of the National Center for Home Food Preservation, rapidly cooling the yogurt culture prevents it from becoming too acidic and tart. Once cooled, flavors or sweeteners can be added to the finished product.

Culture Removal

Some yogurt products are heat-treated to remove the initial live culture bacteria and to extend shelf life. The Code of Federal Regulations issued by the U.S. Food and Drug Administration states that reheating yogurt to a high enough temperature destroys all microorganisms that could cause spoilage, allowing the yogurt to be stored for several weeks and even kept unrefrigerated. These products are labeled with the phrase "heat treated after culturing." Yogurt with live cultures must be refrigerated to prevent the growth of harmful bacteria.

Considerations

While removing the active cultures from the yogurt does extend its shelf life, it also removes the digestive health benefits associated with "good" bacteria. Lactose-intolerant individuals who are able to eat yogurt containing active live cultures may not be able to consume products in which the live bacteria have been removed.

References

• Clairmont College Biology: Yogurt Making Illustrated
• AskDrSears: How to Buy the Healthiest Yogurt: 5 tips
• Michigan State University Extension: Milk Pasteurization
• Code of Federal Regulations: Title 21, section 131.200
• National Center for Home Food Preservation: Fermenting Yogurt at Home

Resources

• Types of Yogurt Bacteria