To improve the survival rate of probiotic in gastrointestinal tract,the Bifidobacterium bifidum F - 35 was microencapsulated into whey protein - based microspheres prepared by transglutaminase - induced gelation/emusification method. The result showed that the microspheres prepared by this method had good spherical structure with a diameter of of(308. 2±16. 2)μm,and the encapsulation yield of B. bifidum F - 35 was 87. 8%±10. 0%. Besides,compared with the non - encapsulated B. bifidum,the survival rate of microencapsulated B. bifidum in the simulated gastric juice and high bile salt solution increased five and two log respectively.

The probiotics,Lactobacillus gasseri and Bifidobacterium bifidum were encapsulated into microcapsules with four types of protein-based coating material,such as soy protein isolation(SPI),whey protein isolation(WPI),sodium caseinate(Casein),gelatin(Gelatin) through transglutaminase-induced emusification/gelation method.The survivability of microencapsulated cells in the four protein-based microcapsules was conducted in simulated gastric juice(SGJ) with or without pepsin.SPI-based microcapsules provided the best protection for microencapsulated cells in all treatments.As for Lactobacillus gasseri,in SGJ with pepsin,the D-value of encapsulated cells in these four protein-based microcapsules were 73.1,59.7,63.9,47.3min,respectively;in SGJ without pepsin,the D-value of encapsulated cells were 246.6,240.5,220.0,90.2min,respectively.As for Bifidobacterium bifidum,in SGJ with or without pepsin,the the D-value of encapsulated cells in these four protein-based microcapsules were 31.7,24.2,22.7,18.7min and 124.3,103.5,97.6,47.8min,respectively.Additionally,some physical properties of these proteins for difference in protective effect on encapsulated cells in SGJ without pepsin were aslo investigated.The result showed that emulsion stability was SPICaseinWPI Gelatin;gel strength was GelatinSPICaseinWPI;permeability to SGJ was GelatinSPI=CaseinWPI;buffer capacity was CaseinWPI=SPIGelatin.It could be deduced that buffer capacity had great influence on the protective effect in low pH condtion,other potential reasons for difference in the protective effect include difference in permeability of protein gels,emulsion stability and gel strength can also affect the protective effect.

Bifidobacterium bifidum F-35 was microencapsulated into whey protein microcapsules (WPMs) by a transglutaminase (TGase)-induced method after optimization of gelation conditions. The performance of these WPMs was compared with that produced by a spray drying method (WPMs-A). WPMs produced by the TGase-induced gelation method (WPMs-B) had larger and denser structures in morphological examinations. Native gel and SDS-PAGE analyses showed that most of the polymerization observed in WPMs-B was due to stable covalent crosslinks catalyzed by TGase. The degradation properties of these WPMs were investigated in simulated gastric juice (SGJ) with or without pepsin. In the presence of pepsin, WPMs-A degraded more quickly than did WPMs-B. Finally, survival rates of the microencapsulated cells in both WPMs were significantly better than that of free cells and varied with the microencapsulation method. However, WPMs-B produced by TGase-induced gelation could provide better protection for microencapsulated cells in low pH conditions and during 1 mo of storage at 4 degrees C or at ambient temperature.

Summary Alginate microspheres containing Bifidobacterium bifidum F‐35 prepared by emulsification/internal gelation were reinforced by blending with pectin or starch or coating with chitosan or poly‐L‐lysine to provide extra protection for the strain. The influence of these treatments on the size of microspheres, encapsulation yield (EY) and protective effect of microencapsulation on the cells was studied. No difference was detected in EY with different types of reinforcement, which was approximately 43–50%. The mean diameter of reinforced alginate microspheres ranged from 117 to 178 μm, reaching a maximum value when starch was incorporated in the alginate matrix. It was observed that the protective effects varied with the type of reinforcement. However, chitosan‐coated alginate microspheres provided the best protection for microencapsulated cells in simulated gastrointestinal tract and during 1 month of storage at 4 °C, and this system could be the comparatively effective vector of bifidobacteria for intestinal delivery.