Lactobscillus acidophilus is an important bacteria for digesting food, as it helps break down food into lactic acids and hydrogen peroxides, which then subsequently kill bad bacteria; it is often given as a supplement to individuals taking antibiotics in order to replace the good bacteria that antibiotics kill when they kill bad bacteria. Additionally, Lactobacillus acidophilus is used to treat vaginal bacterial infections, as well as helping with constipation and diarrhea. Lactobacillus acidophilus is also known as Bifidobacterium. In yogurt, Lactobacillus acidophilus produces carbon dioxide and various acids that affect the flavor and taste.
Streptococcus thermophilus, like Lactobacillus acidophilus, is classified as a probiotic, which means it is also a bacteria that is beneficial to human health. Streptococcus thermophilus is believed to help fight cancer, as it has been proven to stop certain types of nitrates from becoming cancerous. Additionally, Streptococcus thermophilus does not have any protein, which is what harmful bacteria latch on to. Streptococcus thermophilus has also been found to help prevent mucositis, which is one of the negative effects of chemotherapy.
Streptococcus thermophilus and Lactobacillus acidophilus together serve to create yogurt through the process of fermentation. Fermentation in dairy products occurs when the sugar in the milk is broken down by bacteria into lactic acid, which effectively keeps the milk viable passed spoiling. Lactic acid has a naturally sour taste. In addition to creating lactic acid from sugar, Streptococcus thermophilus breaks down caesin, the main protein in milk, which then gives yogurt its thick texture.
Good yogurt has a 1-1 ratio of the two bacteria, as Streptococcus thermophilus creates the texture, but the byproducts of Lactobacillus acidophilus counteract the sourness of the lactic acid being made. There may be up to 10 billion bacteria per gram of yogurt. Natural yogurt is not sweet, though sugar is often later added. In addition to the health benefits of the bacteria, yogurt is also a good source of calcium and protein.