An erythromycin-resistant strain of probiotic Lactobacillus paracasei ssp. paracasei LBC-1 (LBC-1e) was added to part-skim Mozzarella cheese in alginate-microencapsulated or free form at a level of 10(8) and 10(7) cfu/g, respectively. Survival of LBC-1e and total lactic acid bacteria (LAB) was investigated through the pasta filata process of cheese making (in which the cheese curd was heated to 55 degrees C and stretched in 70 degrees C-hot brine), followed by storage at 4 degrees C for 6 wk and simulated gastric and intestinal digestion. This included incubation in 0.1 M and 0.01 MHC1, 0.9 MH3PO4, and a simulated intestinal juice consisting of pancreatin and bile salts in a pH 7.4 phosphate buffer. Some reductions were observed in both free and encapsulated LBC-le during heating and stretching, with encapsulated LBC-le surviving slightly better. Changes in total LAB losses during heating and stretching did not reach statistical significance. During storage, a decrease was observed in total LAB, but no statistically significant decrease was observed in LBC-1e. Survival during gastric digestion in HCl was dependent on the extent of neutralization of HCl by the cheese, with more survival in the weaker acid, in which pH increased to 4.4 after cheese addition. The alginate microcapsules did not provide any protection against the HCl. It is interesting that survival of the encapsulated LBC-le was greater during incubation in H3PO4 than in the HCl gastric juices. Proper selection of simulated gastric digestion media is important for predicting the delivery of probiotic bacteria into the human intestinal tract. Neither free nor encapsulated LBC-1e was affected by incubation in the pancreatinbile solution. Based on the level of probiotic bacteria in cheese needed to provide a health benefit and its survival during simulated gastric digestion, as determined in this study, it should theoretically be possible to lower the amount that needs to be ingested in cheese by up to a factor of 103 compared with other fermented dairy foods or when consumed as supplements.