Abstract

When developing new probiotic foods, their protective properties in maintaining viability of probiotics under gastrointestinal conditions should be evaluated. In the current study, human upper gastrointestinal tract simulator (GITS) was used to compare the effect of different food matrixes on the survival of Lactobacillus rhamnosus GG (LGG). pH-auxostat was chosen for the cultivation of LGG cells to obtain culture samples in the same physiological state at maximum growth rate for the GITS experiments. The LGG culture was centrifuged and fast frozen in liquid nitrogen in various liquid food matrixes (commercial UHT milk, soymilk, apple juice, titrated apple juice, whey protein powder drink and M.R.S. Broth as reference) and stored at -40⁰C. During 3-month storage, reduction of viability was significant only for apple juice. In the GITS experiments, bile had a greater negative impact on LGG than acid conditions, also the effect of food matrix was noted - in the case of milk, soymilk and whey protein powder drink only the highest concentration of bile (0.4%) caused a significant drop in the viability of bacteria when compared to apple juice. To maximize the health benefits of foodstuffs, it should be taken into account that the survival of probiotics during fast freezing, storage and gastrointestinal passage is dependent on the food matrix.

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