Intestinal microbiota in rats fed with tofu (soy curd) treated under high pressure

The present study was carried out to assess the effect of intestinal microbiota in laboratory animals fed with tofu treated under high pressure. The counts of viable mesophilic bacteria and total enterobacteria in the three different groups assayed went down in the rats fed with a diet of untreated tofu. Significant differences ( p <= 0.05) for these microorganisms were found in the rats fed with untreated tofu when compared with the rats of the control group. However, when both tofu diets were compared the counts of mesophilic bacteria went up in the treated tofu and significant differences ( p <= 0.05) were found between treated and untreated tofu diets. Counts of lactic acid bacteria rose in both tofu diets and particularly in the treated tofu, but no significant differences ( p >= 0.05) were found in both tofu diets. Nevertheless significant differences were found with both tofu diets and the control. Some lactic acid bacteria have been identified in tofu diets, such as Lactobacillus plantarum, Lactobacillus acidophilus, Bifidobacterium infantis and also Streptococcus spp. The results for faecal enterococci, faecal coliforms and spores of sulphite- reducing clostridia showed similar values in the three diets. The treated tofu diet in each case presented higher values than the untreated tofu diet, especially for lactic acid bacteria, which means that high- pressure treatment produces a beneficial effect for tofu, owing to the increase of lactic acid bacteria. In conclusion, untreated and treated tofu diets act as " functional food" increasing the number of lactic acid bacteria and reducing the number of Enterobacteriaceae, especially those that are pathogenic, and opportunistic pathogenic bacteria.