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Category: Applied and Industrial Microbiology; Food Microbiology
Fermented Dairy Products, Page 1 of 2
< Previous page | Next page > /docserver/preview/fulltext/10.1128/9781555815912/9781555814076_Chap35-1.gif /docserver/preview/fulltext/10.1128/9781555815912/9781555814076_Chap35-2.gifAbstract:
The primary microflora used in the production of fermented milk products are the homofermentative lactic acid bacteria (LAB). Additionally, yeasts, molds, and several other species of bacteria, including heterofermentative LAB, may be added to specific products; however, their purpose is not for acid development but for the production of flavor components or carbon dioxide. In some fermented dairy products, additional bacteria, often referred to as secondary microflora (but essential to flavor development), are added to influence flavor and alter texture of the final product. The use of nonstarter LAB, especially lactobacilli, as adjunct flavor cultures is a burgeoning research area and is practiced commercially. Proteolytic systems in LAB contribute to their ability to grow in milk and are necessary for the development of flavor in ripened cheeses. The production of high-quality fermented dairy products is dependent on the proteolytic systems of LAB. Bacteriophage infection may lead to a decrease or complete inhibition of lactic acid production by the starter culture. This has a major impact on the manufacture of fermented dairy products, as lactic acid synthesis is required to produce these products. Researchers have begun to characterize host components required for bacteriophage adsorption. It is now thought that bacteriophages initially interact reversibly with cell envelope-associated polysaccharide and then interact irreversibly with cell membrane protein(s).
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Lactose metabolism in homofermentative LAB.
Lactose metabolism in heterofermentative LAB.
Pyruvic acid and citric acid metabolism in LAB. Abbreviations: CoA, coenzyme A; Tpp, thiamine pyrophosphate.
Schematic representation of the lactococcal proteolytic system. Abbreviations: PrtP, cell-envelope-associated proteinase; Opp, oligopeptide transport system; Dtp, di/tripeptide transport systems; AAT, amino acid transport systems; EP, endopeptidases; AP, amino-peptidases; TP, tripeptidases; DP, dipeptidases.
Microorganisms involved in the manufacture of cheeses and fermented milks
Peptidases purified and characterized from lactococci