Survival and proteolytic capacity of probiotics in a fermented milk enriched with agave juice and stored in refrigeration

Abstract

In this study, the survival and proteolysis of lactic acid bacteria Lactobacillus casei Shirota and Lactobacillus rhamnosus GG were measured in fermented milks enriched with agave juice and inulin. Fermentations were terminated at pH 4.5 and stored for 21 days at 4 °C. Survival was determined by viable count in MRS-agar. The production of free amino groups was performed by the TNBS method and peptide separation was performed by SDS-PAGE. During fermentation, pH decreased faster in milk with agave juice than with inulin. There was no significant difference in the concentration of free amino groups (0.632 ± 0.007 and 0.627 ± 0.007 mg/L) between the two fermentation systems for any microorganism. The concentration of lactic acid bacteria in the presence of agave juice was higher than the recommended concentration for probiotic foods (7.59 log CFU/mL for L. rhamnosus GG and 8.26 log CFU/mL for L. casei Shirota). The production of free amino groups and peptides of low molecular weight continued in refrigeration and was higher in systems with agave juice. This could represent a proteolytic activation in the presence of this carbon source. The results showed that agave juice might be a functional ingredient with prebiotic character in symbiotic systems.