Novel Applications of Polysaccharides from Lactic Acid Bacteria: A Focus on Kefiran

Abstract

The food industry is constantly searching for new food components to improve the texture and mouth-feel of food products; moreover, health-promoting capacity of food ingredients is also desirable. In recent years, exopolysaccharide (EPS)-producing lactic acid bacteria (LAB) have gained attention due to their major role in functional f oods and for improving the sensorial properties of fermented products. Certain LAB excrete a wide diversity of polysaccharides with respect to their monomer composition, molecular weight (MW), structure, and functionalities. These extracellular components or EPS can impart functional properties to food and additionally, may confer beneficial health-promoting properties. The role of EPS from LAB in the dairy food industry (i.e. fermented milks and cheeses) is well documented. Also, the addition of EPSproducing LAB to cereal products or their use as food additives have been successfully applied thus broadening their field of application. Kefiran, a high-MW EPS produced by microorganisms present in the grains of the fermented milk kefir, has displayed novel applications in the food industry. Kefiran, which has a Newtonian behaviour in diluted solutions but pseudoplastic at high concentrations, improves the viscosity and viscoelastic properties of acid milk gels. This EPS is also able to form gels at low temperatures in addition to brittle and rigid films. However, glycerol addition confers it extremely high elongation values, allowing comparable flexibilities to those of synthetic material. Moreover, several health-promoting properties of kefiran such as immuno modulation or epithelium protection have been reported . Furthermore, kefiran has the ability to antagonize biological activity of Bacillus cereus on Caco-2 cells thus providing new perspectives for the role of this bacterial EPS in functional foods.