Resumo

The matrix composition of a probiotic food and the storage period may significantly influence the survival of probiotics during passage through the gastrointestinal tract (GIT). The effect of goat milk and cow milk in synbiotic petit-suisse cheeses, as well as the storage period influence on the survival of Lactobacillus paracasei LPC-37 (LPC) to GIT conditions simulated in vitro were investigated throughout 28 days of storage at 4 °C. The pilots trials of synbiotic petit-suisse cheeses of goat milk (GC) and cow milk (CC) with açai pulp were prepared with the starter culture S. thermophilus TA40 and the LPC probiotic culture, and the prebiotics ingredients inulin and FOS. The in vitro survival assays were performed at 1, 7, 14, 21, and 28 days of storage at 4 °C. During the in vitro assay, the pH was adjusted from 2.0 (gastric phase/2h) up to 7.0 (end of enteric phase/6h) and pepsin, lipase, pancreatin, and bile solutions were added to simulate the gastric and enteric conditions. Aliquots of 1 mL were plated after 0 (T0), 2h, 4h, and 6h in acidified MRS agar (pH 5.4) for the enumeration of viable cells. The survival rate (SR%) after the gastric (2h) and enteric (6h) phases were calculated according to the equation: SR % = (log CFU N1/ log CFU N2) x 100%, where: N1 = the total viable count of LPC after simulated gastric and/or enteric phase and N2 = the total viable count of LPC before simulated GIT (0h). Data were analyzed by ANOVA and the mean values were compared using the Tukey test at P<0.05. The LPC populations during the storage period were 7.81 to 8.22 log CFU/g and 8:33 to 8.68 log CFU/g for GC and CC, respectively. After the gastric phase (2h), a decrease of 4 log cycles in both cheeses analyzed and during the whole storage period was observed. The SR% after 2h of assay was significantly different (p<0.05) between the GC and CC cheeses at 7 and 28 days. After 6h of assay, the storage period showed to be a limiting factor in the survival of LPC for both cheeses, and after 28 days of storage populations were less than 2.67 log CFU/g. Additionally, the SR% were 47.03% and 48.81% on the first day of storage and decreased to 32.46% and 30.04% after 28 days of storage for GC and CC, respectively. The type of milk used had no significant effect on the survival of LPC, since the probiotic populations decreased similarly in both cheeses. However storage was a limiting factor in survival, with significant reductions with time.