The role of exopolysaccharide produced by Lactococcus lactis subsp cremoris in structure formation and recovery of acid milk gels

The effect of exopolysaccharide (EPS) produced by Lactococcus lactis subsp. cremoris JFR1 on milk fermentation and recovery of gel structure after stirring was studied using rheology and diffusing wave spectroscopy. Skim milk fermented with an EPS-non producing (EPS-) strain of L. lactis served as control. The production of EPS was not sufficient to affect the stages preceding aggregation. No differences were found in the changes in diffusion coefficient, radius and turbidity parameter of casein particles up to the point of gelation between EPS+ and EPS- samples. However, the presence of EPS significantly increased the storage modulus and viscosity of milk gel, and reduced the ability of the gel to recover after shearing. This study indicates that although the present EPS does not affect the preliminary stages of gelation, it is produced in sufficient quantities after gelation to significantly alter the structure of milk gels in their set or stirred form. (C) 2011 Elsevier Ltd. All rights reserved.