Abstract: Different yogurt curd samples were manufactured by lactic acid bacteria strains and the ropy-strain exopolysaccharides, furthermore, the microstructure and texture properties of the samples were measured. The results indicate that, the mechanism of lactic acid exopolysaccharides reacting with yogurt curd mainly was space baffle effect resulting from the size of the neutral exopolysaccharides themselves which were exclusive from casein in yogurt curd, the space baffle effect interrupted the link ways of casein micelles and thereby dynamically influence the construction of three-dimensional net structure of casein micelle. A novel view point was brought forward that the influence effect of the lactic acid bacteria exopolysaccharides from yogurt on yogurt curds had great things to do not only with the size and structure of exoploysaccharides but also more importantly with the adding ways, time, speed, concentration of exopolysaccharides. Furthermore, the reasons were made clear that the effect of using ropy starter and making a ropy yogurt could not be replaced by adding stabilizer reagents directly.

Key words: Exopolysaccharide, Yogurt curd, Space baffle effect, Mechanism