Production, isolation and characterization of exopolysaccharides produced by Lactococcus lactis subsp cremoris JFR1 and their interaction with milk proteins:: Effect of pH and media composition

The aim of this work was to study exopolysaccharides (EPS) produced by Lactococcus lactis subsp. cremoris (JFR1), and their interactions with dairy proteins. The highest viscosities were obtained in media (permeate from filtration with polyvinylidene fluoride (PVDF) 0.1 mu m) with added protein at pH 5.8 and 5.5. Isolated EPS showed a rheological behaviour different from that of the whole fermented media. The size of the EPS was measured using size exclusion chromatography coupled with light scattering detection. Results suggested that molecules with higher molecular mass and a more compact structure were produced from fermentation at pH 5.5 than molecules produced from fermentation at pH 6.5. Studies using dynamic light scattering demonstrated that EPS molecules are negatively charged and interact with whey proteins at acidic pH. It was concluded that the impact of EPS on textural properties is determined not only by the molecular characteristics but also by the ability to interact with proteins. (c) 2008 Elsevier Ltd. All rights reserved.