A large variety of microorganisms have been employed in food fermentations. Yeast and mold species commonly used are listed in Table 2, and bacterial species are listed in Table 3. The two lists represent a compilation of the species found in commercially available cultures (2-10, personal communications by H. Heap and M. B. Prevot, 2002) as well as those commonly found in food fermentations (11-14). The lists are not complete with respect to species that are only occasionally found in fermented foods. Of the large number of microorganisms listed, a few are exceptionally widely used. The top three are Saccharomyces cerevisiae, Lactococcus lactis, and Streptococcus thermophilus.
Saccharomyces cerevisiae is used as baker's yeast, brewer's yeast, inoculums for wine fermentations, food and feed additives, and as flavor-generating cultures in dairy and meat products. The annual production of baker's yeast is approximately 1 million tons; the
Table 2 Yeast and Mold Species Commonly Used in Food Fermentations
Saccharomyces oryzae famata kefyr krusei lipolytica
Parapsilosis valida candidum album camemberti chrysogenum nalgiovense roqueforti bayanus cerevisiae
Soy sauce Meat
Fermented milk Fermented milk
Cheese, meat Fermented milks Baker's yeast, brewing,
Cheese, fermented milks wine-making, cheese, fermented milks, meat, vegetables, and probiotics volume of the yeast production exceeds the combined production of all other microorganisms by about two orders of magnitude. The bulk production of yeast is a commodity quite different from the high value, low volume yeast strains produced for inoculating wine fermentations, and is also quite different from all the other inoculants for food fermentations.
Lactococcus lactis is the most widely used lactic acid bacterium. L. lactis is used for the production of cheese, butter, buttermilk, and other fermented milks and, to some extent, is used in meat, bread, and vegetable products.
Streptococcus thermophilus is the second most-used lactic acid bacteria. It is used in the dairy industry for the production of yogurt and a variety of other fermented milk products, and for the production of several cheeses, most notably mozzarella and pizza cheese. Due to the high acidification activity, S. thermophilus is often used in combination with other lactic acid bacteria to increase the speed of the fermentation.
Of the Lactobacillus species, L. delbrueckii and L. acidophilus are used in relatively large volumes, especially in dairy products; L. acidophilus is also used in various probiotic products. Several species of Bifidobacterium are used as probiotic cultures in fermented foods and food supplements. The other species listed in Tables 2 and 3 are produced in much smaller volumes, but for some strains the contribution to the final product is so essential that the value of the culture can be very high although the volume is small.
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