Both acidophilus milk and sweet acidophilus milk are inoculated with the bacterium Lactobacillus acidophilus. Many health practitioners believe that this bacterium, a normal member of the human intestinal flora, aids in digestion. Regular acidophilus milk is produced by adding the bacterium to vats of skim milk as part of the fermentation process; it has a characteristic sour taste. When the bacterium is added to pasteurized milk and packaged without fermentation, sweet acidophilus milk, which lacks the characteristic sour taste, is produced.