Yogurt Fermentation Basics

• Yogurt is made by inoculating warmed milk with a starter culture that is generally made up of Lactobacillus bulgarius and Streptococcus thermophilus. These two types of lactic acid bacteria will, under the right conditions, transform the sugar in the milk into lactic acid, giving it its unique sour taste and texture. The entire process of fermentation of milk into yogurt takes place in about 12 hours and requires a controlled heated environment to promote the reproduction of these healthy bacteria at a rapid rate.

Living Yogurts

• All types of yogurt available have live bacteria in them at the time of fermentation. The most common microorganisms present are Lactobacillus bulgarius and Streptococcus thermophilus, however, many yogurts are further fortified with even more bacteria -- such as probiotics and Bifidobacterium bifidum -- that help to promote overall gut health. Because all of these types of yogurt have a high level of nutrients compared to the amount of fat included, yogurt is a nutrient-rich food similar in makeup to milk.

Microorganisms After Fermentation

• Some types of yogurt are heat-treated after fermentation to create a more stable product. This process kills all the bacteria present at the time of fermentation, including these healthy bacteria. To select yogurt that has active bacteria in it, look for those products labeled with a "Live and Active Culture" seal on them. This seal administered by the National Yogurt Association ensures that a yogurt product has at least 100 million cultures per gram at the time of manufacturing or 10 million cultures per gram for frozen yogurt products.

Microorganisms and Your Health

• The microorganisms present in yogurt have long been praised for their beneficial qualities on overall and intestinal health. As the most commonly known probiotic food in the United States, yogurt is widely available. However, many of the popular types of yogurt are heavily sweetened or artificially sweetened, taking away from some of the positive aspects of yogurt. Look for live yogurts that are minimally sweetened to recognize the most health benefits. Other less common foods packed with microorganisms that have the same benefits in the body include kombucha, kefir, kimchi and sauerkraut.