Reference Number: 32
Lactic acid bacteria (LAB) that produce exopolysaccharides (EPSs) play an important role in the dairy industry because of their contribution to the consistency and rheology of fermented milk products. The EPS polymers can be considered as natural biothickeners because they are produced in situ (within the culture medium) by the LAB-starters that have General Recognised As Safe status (GRAS). The physico-chemical properties of EPSs determine their viscosifying efficiency. Hence, the knowledge of the structure–function relationship of these biopolymers is crucial in order to choose or design polymers for a specific technological application. In addition, health benefits have been attributed to some of these EPSs, particularly antitumor and immunomodulating activities. Being a complex carbohydrate similar to fibre, a prebiotic role has also been suggested. However, almost all studies were performed in vitro and scarce information is available concerning in vivo experiments with oral administration. This overview focuses on the recent information about the functional properties of lactic acid bacterial EPSs, including both technological and health-promoting aspects.
SIGNIFICANCE OF THIS STUDY
Several lactic acid bacterial (LAB) strains in sourdough fermentation can contribute to improve the texture and viscosity of breads and other foods by means of the synthesis of polysaccharides or complex sugars called exopolysaccharides (EPSs). LAB, like many other bacteria, are able to produce several types of polysaccharides that are classified according to their location relative to their outer cases or cell walls. The polysaccharides are normally produced by the bacteria solely for their own protection. Those that are excreted outside the cell wall are called exo-cellular (meaning outside of their cell wall) polysaccharides or EPSs. The EPSs produced by LAB can be divided into two categories: homopolysaccharides, containing only one type of sugar unit (monosaccharides) and heteropolysaccharides which are composed of repeating units,varying in size from 2-6 sugar units. During the sourdough process, the formation of both homo and heteropolysaccharides contribute to the elasticity of the dough and overall fibre content of the bread. The use of EPS-producer ‘‘ropy’’ strains is common in the manufacture of fermented milks and yoghurt in order to obtain a proper consistency.