Question

Study of interactions between anionic exopolysaccharides produced by newly isolated probiotic bacteria and sodium caseinate.

Answer 1

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- The present study aims to evaluate the interactions between four exopolysaccharides (EPS) produced by probiotic bacteria and sodium caseinate (Cas) in order to simulate their behavior in dairy products. Complexation between the produced EPS samples and Cas was investigated as a function of polysaccharide to protein ratio. The highest turbidity and average size of complexes were formed at an EPS/Cas ratio of 3 (corresponding to 1 g/L of EPS and 0.33 g/L of Cas) as a result of the combination of individual complexes to form aggregates. Zeta potential measurements and Cas surface hydrophobicity results suggested that complex formation occurred essentially through electrostatic attractions with a possible contribution of hydrophobic interaction for EPS-GM which was produced by Bacillus tequilensis-GM. Afterwards, the effect of pH on the complexation between biopolymers was studied when EPS and Cas concentrations were maintained constant at 1 and 0.33 g/L, respectively. pH was adjusted to 3.0 and 3.5, respectively. Results showed that the highest amount and sizes of EPS/Cas complexes were formed at pH 3.5 and that EPS-GM enabled to obtain the biggest and highest amount of aggregates. Therefore, the obtained results support the fact that the simultaneous presence of EPS and Cas in dairy products results in complexes formation via electrostatic interactions depending on EPS/Cas ratio and pH of the medium.