| Probiotics are a sort of the bacteria that already exist and grow in humans’ and animals’ intestinal tract. Various health related properties of different probiotic strains, such as maintain and modulate ecological equilibrium, improve the digestion and absorption of nutriment, inhibit the growth of pathogens and improve immunity of the host, are well documented and belived to play a beneficial role in the ecosystem of the human and animal intestinal tract. However, the loss of bioactivity, that is the loss of living probiotic cell numbers during processing, storge, and gastrointestinal transit caused by various stress factors is an important issue, which limited its application in industry and its beneficial effects to human and animals and has to be avoided. Hence the protection of living probiotic cells became an important issue. In this context, we use the combination of different protiens and polysaccharids to encapsulate probiotics through spray drying technology. The effects of different formulation on the survival of probioitcs during spry drying, simulated gastrointestinal digestion and storage were studied and analyzed. Futhrermore, an animal trial using pigs as the target animal was applied. The digestion, release and colonization properties, as well as the inhibition property to Salmonella of encapsulated probiotics were then carried out and analyzed.First, co-encapsulation of low melting point fat(HMF) with probiotic bacteria to minimize their heat damage during spray drying was studied. Three Lactobacillus isolates(LB1, S64 and K67) as potential probiotic bacteria were spray dried in 10 % w/v sodium caseinate(NaCas) in the presence of either HMF or vegetable oil as a control. Addition of HMF, but not vegetable oil, significantly increased the survival of isolate LB1(from 15 % to 63 %) in the spray dried powders. Differential scanning calorimetry(DSC) results showed that the melting enthalpy increased with the concentration of HMF, which is in accordance with the survival rate of LB1 after spray drying. In addition, isolates LB1 and K67 co-encapsulated with HMF showed improved survival on NaCl-MRS agar compared to the control, indicating a reduction in their cellular damage.Then, with the purpose of enhancing the gastric resistance and storage properties of NaCas-HMF based probiotic microparticles, incorporating different carbohydrate polymers into the microparticles was applied. Probiotic bacteria was spray dried in NaCas solution containing HMF combined with one of: maltodextrin, pullulan, gum ghatti or gum arabic(GA). Probiotic bacteria showed good survival after spray drying only in those formulated with gum ghatti or gum Arabic. Addition of GA and gum ghatti to NaCas showed a positive effect on the in vitro gastric resistance of probiotic bacteria, whereas maltodextrin and pullulan exerted a negative influence. Among the formulations tested, microparticles made from a blend of NaCas and GA showed the highest glass transition temperature(Tg), corresponding to the best survival of probiotic bacteria during storage for up to 16 weeks in water activity range of 0.11- 0.76. The presence of two Tgs in the NaCas-pullulan matrix suggested that phase separation was occurring, which could partially account for its poor protection capacity. Encapsulated probiotic bacteria in all matrices showed good release properties in the presence of pig intestinal digesta; probiotic bacteria release from microparticles was complete in less than 1 h.The gastric resistance and storage properties of alginate(AG) based probiotic microparticles by incorporating different proteins were investigated. Lactobacillus zeae isolate LB1 was spray dried in AG solution combined with either soy protein isolate(SPI) or sodium caseinate(NaCas). Addition of SPI or NaCas to AG showed a positive effect on the in vitro gastric resistance of L. zeae LB1 and also resulted in a hollow internal structure. Among the formulations tested, microparticles made from a blend of NaCas and AG showed the highest glass transition temperature(Tg), corresponding to the best survival of isolate LB1 during storage for up to 16 weeks in water activity range of 0.11- 0.76. The presence of two Tgs in the NaCas-AG particle suggested that phase separation was occurring, which proved to have positive protection effect on the viability of encapsulated probiotic bacteria during storage.Finally, in order to investigate the digestion, release, and colonization properties, as well as the inhibition property to Salmonella in pig gastrointestinal tract, encapsulated probiotcs were applied and gavaged to pigs. The results showed that with encapsulation, the probiotics could pass through the stomatch smoothly and release and colonize into the intestinal tract. Compared with the unencasulated probiotic group, the concentration of probiotc in feces increased significantly. For the pigs infected by Salmonella, after gavaged with encapsulated probiotcs, the Salmonella concentration in jejunum, illeum, cecum and colon decreased by 0.99, 2.17, 1.77, 1.41 log CFU/mL, respectively. |
PDF Full Text Request