What makes yogurt - well, yogurt? The words "live and active cultures" refer to the living organisms, Lactobacillus bulgaricus and Streptococcus thermaophilus, which convert pasteurized milk to yogurt during fermentation. Note that the milk is pasteurized before culturing to remove any harmful bacteria. The process is very similar to that used when making beer, wine or cheese, in that beneficial organisms ferment and transform the basic food. This fermentation process is what creates yogurt, with its unique taste, texture and healthful attributes. Yogurt is a fermented milk product which originated in Turkey in which a mixed culture of Lactobacillus bulgaricus (or occasionally L. acidophilus ) and Streptococcus thermophilus produce lactic acid during fermentation of lactose. The lactic acid lowers the pH and makes it tart and causes the milk protein to thicken. The partial digestion of the milk when these bacteria ferment milk makes yogurt easily digestible. In addition, these bacteria will help settle GI upset including that which follows oral antibiotic therapy by replenishing non-pathogenic flora of the gastrointestinal tract. A powder is a dry, bulk solid composed of a large number of very fine particles that may flow freely when shaken or tilted. Powders are a special sub-class of granular materials, although the terms powder and granular are sometimes used to distinguish separate classes of material. In particular, powders refer to those granular materials that have the finer grain sizes, and that therefore have a greater tendency to form clumps when flowing. Granulars refers to the coarser granular materials that do not tend to form clumps except when wet.