ABSTRACT
Modern dairy microbiology began with the study of the natural acidification process that occurs when milk, cheese whey, or buttermilk (from cultured butter manufacture) are held for a time. These acidified products had long been used as inocula to produce cheese, butter, and cultured milks, but the resulting fermentations were undependable and of uneven quality. Pasteur, in 1857, was the first to demonstrate that the lactic fermentation was of microbial origin; disputing the accepted theory of the time that chemical degradation of sugar to lactic acid resulted in spontaneous generation of microorganisms (Brock, 1961). It was not until 1878 that Lister isolated pure cultures of the lactic acid bacteria responsible for milk acidification (Brock, 1961). In the 1880s, Conn in the United States, Storch in Denmark, and Weigmann in Germany demonstrated the advantages of using selected lactic acid bacteria to culture cream for butter manufacture (Knudson, 1931; Cogan, 1996). Commercial production and the use of starter cultures grew rapidly and was widespread at the beginning of the 20th century. The advantages of using starter cultures to initiate fermentation were convincing. Before the use of commercial starter cultures, Cheddar cheese took 6-7 h to produce, and much of the product was of too poor a quality to be sold (Conn, 1895). Slow fermentation was also a public health threat, because milk for cheese manufacture was not pasteurized. Currently, most cultured dairy products are produced using
commercial starter cultures that have been selected for a variety of desirable properties in addition to rapid acid production. These may include flavor production, lack of associated off-flavors, bacteriophage tolerance, ability to produce flavor during cheese ripening, salt tolerance, polysaccharide production, bacteriocin production, and heat sensitivity.
