Exopolysaccharide-producing lactic acid bacterium strains as functional starter cultures in the production of fermented milk

摘要

Functional starter cultures of lactic acid bacteria for the production of fermented foods are starter cultures that possess at least one inherent functional property that may contribute to the organoleptical, technological, nutritional or health properties of the food. A typical example is the use of exopolysaccharide-producing strains in the production of fermented milk. Lactic acid bacteria produce a wide diversity of exopolysaccharides with respect to monomer composition, primary structure, andmolecular mass. The repeating unit composing heteropolysaccharides generally consists of galactose, glucose, and rhamnose, and sometimes also fucose, aminosugars, and glucuronic acid are present. So, the question raises if a correlation exists between the structure of the exopolysaccharides and their rheological properties. Also, some strains produce only high-molecular-mass exopolysaccharides, others produce only low-molecular-mass exopolysaccharides, while still others produce both types of exopolysaccharides. Furthermore, the amount of exopolysaccharides produced may differ considerably. Hence, a clear correlation between the apparent viscosity of the medium and the amount of exopolysaccharides produced is not evident when comparing different strains. Rational strain selection and an adapted process technology may contribute to an improved texture of yogurts and other fermented milk. For instance, a temperature and pH-controlled exopolysaccharide production followed by a fast acidification resultsin an increased exopolysaccharide yield, an enhanced viscosity, and an improved texture of the resulting fermented milk.