| Probiotics are welcomed by millions of consumers throughout the world due to its various beneficial functions.However,advances in probiotic markets are always restrained by a low viable loading capacity,limited viability and poor long-term storage stability,so studies on the efficient encapsulation of probiotics are vitally important to the development of probiotic industry.In this study,porous cellulose microgels were used as the houses for the accommodation of Lactobacillus plantarum(L.plantarum).The microcosmic structure of cellulose microgels was manipulated and its effect on the probiotic encapsulation behavior was investigated.The addition of Ca-alginate and freeze-drying protectants could realize the targeted delivery of probiotics and improve the viability of probiotics.The effect of microencapsulation and composition modification on digestive tolerance and storage stability of probiotics was further studied.The obtained information could provide theoretical foundation for exploiting efficient and stable probiotic products.The main research contents and results are as follows:(1)Manipulating the microcosmic structure of cellulose microgels: The round porous cellulose microgels were prepared by the emulsion method,and the release viable cell was up to 3.1×1010 cfu/g.Granules of calcium carbonate as porogenic agents made the cellulose microgels with different porosity,and a series of characterizations manifested that the modified cellulose microgels showed no difference with cellulose microgels in the aspects of chemical structure,crystal structure,surface elements and thermal stability.However,the pore morphology and pore structure of cellulose microgel had an influence on the distribution of L.plantarum cells in microgels,and the released viable cell amount was basically proportional to the porosity,which indicated the encapsulation of probiotic cells could be controlled by manipulating the microstructure of cellulose microgels.Besides,the result of confocal laser scanning microscopy proved that the L.plantarum cells penetrated deep into the core of cellulose microgels.(2)Study on the digestive tolerance of L.plantarum cells: The cellulose/Ca-alginate microgels(CAMs)and cellulose/Ca-alginate(ACL)beads with good p H-responsibility were prepared by emulsion method and extrusion method,respectively.The porous property of CAMs was positively related to the cellulose content in the CAMs,and the CAMs could accommodate viable L.plantarum cells as high as 109 cfu/g.However,ACL beads showed an advantage over CAMs on the targeted delivery of L.plantarum cells due to the unique core-shell structure.As for ACL beads,cellulose microgels with L.plantarum cells could only release out in simulated intestinal fluid(SIF),and the porous structure of cellulose microgels helped to sustain the viable cell release for a longer duration.After exposure to simulated gastric fluid(SGF),ACL beads showed sustainable release of L.plantarum cells lasting for 360 min in SIF,and the release viable cell was up to 3.9×1010 cfu/g.(3)Study on the storage stability of L.plantarum cells: Vacuum freeze-drying method was used to further improve the storage stability of ACL beads.Firstly,the optimum formula of freeze-drying protectants(FP)was investigated and the result was as follows,2% glycerin,10% trehalose and 10% whey protein isolate.The addition of this FP in ACL beads made the resulting composite(ACFP)capsules with better shelter for L.plantarum cells during the freeze-drying process,and the release viable cell amounts from ACFP capsules before and after lyophilization were 4.9×107 cfu/m L and 2.9×107 cfu/m L,respectively.After vacuum freeze-drying treatment and SGF digestion,ACFP capsules still released viable L.plantarum cells as high as 2.6×106 cfu/g.When the storage temperature was 4 oC and after storage for 160 days,the dry ACFP capsules still released viable L.plantarum cells as high as 3.3×10~6 cfu/g. |
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