The survival of selected bacteria in semi-hard experimental cheeses was studied after exposure to human gastric and duodenal juices in an ex vivo model. Experimental cheeses (10 and 28% fat) were supplemented with different strains of Lactobacillus sp. and Propionibacterium sp. and ripened for 7 and 70 weeks. After digestion, greater numbers of the adjunct bacteria we rerecorded in the 7-week-old cheeses compared to the well-matured cheeses (70 weeks). The bacterial survival was strain dependent, and influenced by the fat content of the cheese. Lactobacilli showed better survival, especially when in low-fat cheeses. The strains of propionibacteria also survived well during the digestion of the low-fat cheeses. The results confirmed that cheese can potentially be a good carrier matrix for bacteria to the intestine. In addition, it has been shown that different strains present in cheese have different abilities to survive the conditions of the gastrointestinal tract. Younger cheese was indicated to be a better carrier, possibly because the bacteria present in those cheeses have had shorter exposure to the stress conditions occurring in cheese during prolonged maturation.
Significance and impact of the study: Cheese can function as a suitable vehicle for the delivery of a variety of food-related micro-organisms to the intestine. Young cheese as well as low-fat cheeses are better carrier matrixes than full-fat and/or more well-ripened cheeses. Most of the lactobacilli and all the propionibacteria survived well during digestion of the low-fat cheeses. This study also showed the ability of cheese lactobacilli and PAB to survive the severe conditions of GIT.
Keywords: cheese; ex vivo digestion; lactic acid bacteria; propionic acid bacteria; survival rate.
© 2016 The Society for Applied Microbiology.