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Lactobacillus bulgaricus

Yoghurt is a milk product which is very popular and which can now be bought off the shelf in many different forms, for example as flavoured yoghurt, frozen yoghurt, skimmed milk yoghurt or full cream milk yoghurt. The basic appeal of yoghurt is as a health food which is high in protein. Yogurts are conventionally obtained by fermentation of milk with a combination of Streptococcus thermophilus and Lactobacillus bulgaricus. During the fermentation, these bacteria use mainly lactose as an energetic substrate, and produce lactic acid which causes the milk to coagulate; when the pH reaches a value of approximately 4.8 to 4.5, this fermentation step is terminated by cooling the product. This product is then kept in the cold during the remainder of the manufacturing and packaging process, and until its consumption. Lactic acid fermentation occurs during the action of bacteria such as Lactobacillus bulgaricus and Streptococcus thermophilus on milk or milk products such as pasteurised milk or concentrated milk with or without optional additives such as milk powder, skim milk powder, whey powder etc. It is L. bulgaricus which produces the typical yoghurt aroma during the fermentation process. Therefore, yoghurt missing or having a reduced titer of metabolic active L. bulgaricus cells miss the aroma components of the typical yoghurt. Thus, such yoghurt (or yoghurt like products) can be very neutral, i.e. flat in taste. This problem is particularly eminent for the production of mild or very mild yoghurt, which as a consequence of the limited growth rate of L. bulgaricus tend to lose a lot of their aroma. Dairy foods are an important source of protein, riboflavin, and calcium, and many people have a dairy disorder. Acquired lactase deficiency is the most common disorder of complex carbohydrate absorption in all populations. Up to seventy percent of the world's population has this disorder, resulting in gastrointestinal symptoms of excessive gas production, abdominal pain, bloating, and diarrhea after consumption of lactose and the by-products of lactose containing foods, e.g., milk, cheese, cakes, eggs, veal, and yogurt. Lactase enzyme replacement products, to date, have generally been useful as a replacement of the deficient enzyme for a short period of time prior to a meal or snack. Lactose-hydrolyzing lactase enzymes are also known to be produced by various yeasts, bacteria, and fungi. Among the organisms useful in hydrolyzing lactose are Saccharomyces fragilis, Torula cremoris, Lactobacillus bulgaricus, Aspergillus oryzae, Aspergillus flavus, and Aspergillus niger. These organisms are cultured and used to prepare lactase enzyme preparations for lactase replacement products.

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