In our master's thesis, we investigated the survival of probiotic bacteria from eight commercial products after simulated in vitro digestion with the addition of three different media: water, orange juice and a meal of cereal flakes with milk. Our aim was to simulate three different scenarios of consumption of probiotic products: on an empty stomach, with fruit juice or with a meal. We also evaluated the consistency of information provided on the products labels. To determine the number of bacteria, we carried out a plate counting method. We simulated digestion with the use of standardised static in vitro digestion model INFOGEST 2.0. Bacterial viability decreased during digestion for all products except for product 5, where it increased. The highest average survival of probiotics was observed in the meal medium and the lowest in the juice medium. The average decrease in bacterial concentration was 0.6 log colony forming units (CFU)/product unit in the meal, 1.1 log CFU/product unit in the water and 1.8 log CFU/product unit in the juice. However, the statistical analysis did not show statistically significant differences within the samples, due to only two replicates. The survival of all bacterial genera was statistically significantly lowest in the juice medium. All products met the declared total number of viable bacteria and all of them reached the recommended value of 6 log CFU/g in all media after simulated digestion. All products contained all legally required information on their labels; however, we detected unauthorised health claims on three of them. Based on our results, we conclude that most products need improved recommendations for their instructions for use. Using the INFOGEST 2.0 method, we were able to verify in which medium the product's bacteria survive digestion best, which can serve as a basis for the labelled recommendations on how to take probiotic products.
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