Fermented Dairy Products

Abstract

The fermented dairy products category contains products with a diversity of flavors, textures, and appearances, all of which are directly dependent on microbial metabolism. The enzymes and metabolites required to produce these products are provided by a diverse set of microorganisms, including molds, yeasts, and bacteria. Of these organisms, homofermentative lactic acid bacteria (LAB) are of the greatest importance, as the manufacture of fermented dairy products is directly dependent on their primary metabolic end product, lactic acid. This chapter describes the potential for production of diacetyl and carbon dioxide from lactose metabolism in lactococci with reduced lactic acid dehydrogenase activity. The main volatile flavor components of fermented milks are acetic acid, acetaldehyde, and diacetyl. Proteolytic systems in LAB contribute to their ability to grow in milk and are necessary for the development of flavor in ripened cheeses. Peptides and amino acids formed by proteolysis may impart flavor directly or serve as flavor precursors in fermented dairy products. The dairy industry has employed improved sanitation regimens, utilized sophisticated starter culture propagation vessels, developed starter culture systems to minimize the impact of phage infection, and isolated and constructed starter strains with enhanced bacteriophage resistance. The power of recombinant DNA approaches is that strains can be constructed that differ in a single defined genetic alteration, e.g., inactivation of a specific gene.