Cultured Dairy Products

". . . during recent years, attention has been directed to soured milk to such an extent that it has become necessary for all who are interested in the handling of milk and milk products to have a knowledge of the subject, as it seems clearly demonstrated that, under proper direction, there is every possibility of its forming an important element in the prolongation of life."

From The Bacillus of Long Life by Loudon Douglas, 1911

Introduction

Milk fermentations must undoubtedly be among the oldest of all fermented foods. Milk obtained from a domesticated cow or camel or goat, some thousands of years ago, would have been fermented within hours by endogenous lactic acid bacteria, creating a yogurt-like product. In fact, the ability to maintain milk in a fresh state before souring and curdling had occurred would have been quite some trick, especially in warm environments. Of course, fermentation and acid formation would have been a good thing since, in the absence of viable lactic acid bacteria, other bacteria, including pathogens, could have grown and caused unpleasant side effects.

Milk is particularly suitable as a fermentation substrate owing to its carbohydrate-rich, nutrient-dense composition. Fresh bovine milk contains 5% lactose and 3.3% protein and has a water activity near 1.0 and a pH of 6.6 to 6.7, perfect conditions for most microorganisms. Lactic acid bacteria are saccharolytic and fermentative, and, therefore, are ideally suited for growth in milk. In general, they will outcompete other microorganisms for lactose, and by virtue of acidification, will produce an inhospitable environment for would-be competitors. Therefore, when properly made, cultured dairy products have long shelf-lives and, although growth of acid-tolerant yeast and molds is possible, growth of pathogens rarely occurs.

Given the early recognition of the importance of milk in human nutrition and its widespread consumption around the world, it is not surprising that cultured dairy products have evolved on every continent. Their manufacture was already well established thousands of years ago, based on their mention in the Old Testament as well as other ancient religious texts and writings. Yogurt is also mentioned in Hindu sacred texts and mythology.And although the manufacturing procedures, the sources of milk, and the names of these products may vary considerably, they share many common characteristics. Thus, dahi (India), laban (Egypt, Lebanon), and jugart (Turkey) are all yogurt-like products whose manufacture involves similar milk handling procedures and depends on the same ther-mophilic culture bacteria. Other products, in particular, kefir and koumiss, evolved from Asia, and are made using various lactose-fermenting yeasts in addition to lactic acid bacteria.

Consumption of Cultured Dairy Products

Yogurt, sour cream (and sour cream-based dips), and cultured buttermilk are the most popular cultured dairy products in the United

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