RESUMO
A comparison between the most investigated alginate-based encapsulating agents was performed in the current study. Here, the survivability of Lactobacillus plantarum microencapsulated with alginate (Alg) combined with skim milk (Sm), dextrin (Dex), denatured whey protein (DWP) or coated with chitosan (Ch) was evaluated after exposure to different heat treatments and in presence of some food additives, during storage and under simulated gastrointestinal condition. In addition, the encapsulated cells were evaluated for production of different bioactive compounds such as exopolysacchar. ides and antimicrobial substances compared with the unencapsulated cells. The results showed that only Alg-Sm maintained the viability of the cells >106 cfu/g at the pasteurization temperature (65 °C for 30 min). Interestingly, storage under refrigeration conditions increased the viability of L. plantarum entrapped within all the tested encapsulating agents for 4 weeks. However, under freezing condition, only Alg-DWP and Alg-Sm enhanced the survival of the entrapped cells for 3 months. All the microencapsulated cells were capable of growing at the different NaCl concentrations (1%-5%) except for cells encapsulated with Alg-Dex, showed viability loss at 3% and 5% NaCl concentrations. Tolerance of the microencapsulated cells toward organic acids was varied depending on the type of organic acid. Alg-Ch and Alg-Sm provide better survival for the cells under simulated gastric juice; however, all offer a good survival for the cells under simulated intestinal condition. Our findings indicated that Alg-Sm proved to be the most promising encapsulating combination that maintains the survivability of L. plantarum to the recommended dose level under almost all the stress conditions adopted in the current study. Interestingly, the results also revealed that microencapsulation does not affect the metabolic activity of the entrapped cells and there was no significant difference in production of bioactive compounds between the encapsulated and the unencapsulated cells.
RESUMO
BACKGROUND: Our study was conducted in two stages; the first stage was to examine the fructose fermentation profile by Lactobacillus (Lb.) casei FEGY9973. The second stage was to investigate the viability properties of Lb. casei either during cold storage of labneh or under simulated gastrointestinal tract (GIT) conditions. METHODS: Labneh as a carrier medium was classified into four treatments; the first one con- tained 2% free cells of Lb. casei as a control. The second, third and fourth treatments used 2% of encapsulated cells of Lb. casei with different capsule materials, including alginate-milk, sodium alginate and κ-carrageenan served as T1, T2 and T3 respectively. The physiochemical, microbiological and sensory properties of labneh during 15 days of cold storage were shown. Moreover, the viability of free and encapsulated Lb. casei sub- jected to some manufacturing and simulated GIT conditions was tested. RESULTS: It was revealed that lactate was the major metabolite in the medium for colonic fermentation, where- as no amounts of ethanol could be detected. Moreover, labneh samples including free cells of Lb. casei had lower pH values than treatments containing microcapsules of Lb. casei. The levels of moisture, acetaldehyde and diacetyle in treatments with different encapsulated materials were increased during the cold storage period. Accordingly, labneh samples with encapsulated Lb. casei had higher sensory scores than the control. In addition, labneh samples with Lb. casei in milk-alginate microcapsules showed a high viability during cold storage and under simulated GIT conditions. A significant decrease in the viability of free or encapsulated Lb. casei was observed at 15 days of cold storage. CONCLUSIONS: Encapsulated Lb. casei by alginate-milk was more resistant during the cold storage period and under simulated gastric conditions than the other two treatments.
