What makes yogurt . . . well, yogurt? The words "live and active cultures" refer to the living organisms—in this case the bacteria, Lactobacillus bulgaricus and Streptococcus thermophilus— which convert pasteurized milk to yogurt during fermentation. The process is very similar to that used when making beer, wine or cheese, in that beneficial organisms ferment and transform the starting material into a “new” food/beverage – grape juice is converted into wine; milk into cheese; water, barley and hops into beer. This fermentation process is what creates yogurt, with its unique taste, texture and healthful attributes.
Some yogurt products are heat-treated after fermentation, which kills the beneficial active cultures found in the yogurt, so to help you identify those yogurt products that contain live and active cultures, the International Dairy Foods Association offers the Live & Active Cultures (LAC) seal. The LAC seal, which appears on refrigerated and frozen yogurt containers, helps you recognize those products containing significant amounts of live and active cultures. The seal is a voluntary identification available to all manufacturers of yogurt whose products contain at least 100 million cultures per gram of yogurt at the time of manufacture. The LAC seal can also be used for frozen yogurt that contains at least 10 million cultures per gram at the time of manufacture. Since use of the LAC seal is voluntary, some yogurt products may contain live and active cultures, but not carry the seal. However, the LAC seal is the only widely recognized, independent verification that a yogurt or frozen yogurt contains significant levels of live and active cultures.
If you are a manufacturer or marketer of yogurt or frozen yogurt and interested in the LAC seal program, additional information on how to obtain the seal can be found here.