Microencapsulation of Bifidobacterium BB-12 in passion fruit juice: evaluation of survival under simulated gastrointestinal conditions

Non-dairy food matrices have been studied as potential carriers for probiotic microorganisms because of the increasing prevalence of lactose intolerance, milk protein allergy and hypercholesterolemia. Fruit juices may represent an ideal vehicle for probiotic cultures. Nevertheless, the viability of probiotics may be suppressed by environmental stress conditions, such as high concentration of organic acids usually found in fruit juices, which are reportedly unfavorable for bacterial viability. However, probiotics must remain viable in adequate quantities in a food product during its shelf life and passage through the gastrointestinal tract (GIT), in order to exert their benefits to the host. Thus, microencapsulation techniques, such as spray drying, have been used to provide suitable protection for these microorganisms when exposed to adverse conditions. The aim of this study was to evaluate the survival of Bifidobacterium BB-12 added to passion fruit juice and microencapsulated by spray drying, using different carrier agents, under simulated gastrointestinal conditions. Therefore, two formulations of passion fruit juice added with bifidobacteria were microencapsulated in a laboratory-scale spray dryer, using maltodextrin or inulin as encapsulating agents (20 % w/v), comprising microcapsules PFM and PFI, respectively. Free cells suspension was prepared with peptone water and was submitted to the same conditions of microcapsules during the assays. The viability of the free and microencapsulated bacteria was determined sequentially in media simulating the conditions prevailing in the human gastrointestinal tract: mouth (pH adjusted to 6.9, addition of α-amylase, 2 min), esophagus-stomach (addition of pepsin, pH adjusted to 2.0 for 90 min), duodenum (addition of pancreatin and bile salts, pH adjusted to 5.0 for 20 min) and ileum (pH adjusted to 6.5 for 90 min). Aliquots of each step were enumerated using MRS agar modified with lithium chloride and sodium propionate and plates were incubated anaerobically at 37 °C for 72 hours. Counts were expressed as log of colony-forming units per gram/mL (log CFU/g or mL). Different susceptibilities were observed among samples during gastrointestinal simulation. No decrease in bifidobacteria counts were detected (p >0.05) after exposure to mouth conditions. However, after exposure to the esophagus-stomach conditions, the viable cell counts decreased (p <0.05) in relation to the initial counts. This step was the most detrimental to the survival of bifidobacteria for all samples, suggesting their sensitivity towards the extremely acidic conditions and pepsin activity. The PFI microcapsules were less susceptible than PFM and the free cells, showing a decrease of 1.03 log CFU/g, while other samples showed reductions of 1.64 and 1.95 log CFU/g, respectively. After the duodenum conditions step, the count of viable cells in PFI microcapsules slightly increased (p <0.05) in relation to previous step, while this behavior was not noted in the other samples. After ileum step, the PFM and free cells samples showed a slight increase in viable bifidobacteria counts, while no significant variations were observed for the PFI microcapsule. The results demonstrated that the use of inulin as encapsulating agent conferred additional protection to the bifidobacteria against GIT stress conditions, being effective in maintaining the viability of probiotic bacteria.