Ainsley Reid A, Vuillemard J C, Britten M, Arcand Y, Farnworth E, Champagne C P
Food and Nutrition Sciences Department and INAF, Laval University Quebec, QC, Canada.
J Microencapsul. 2005 Sep;22(6):603-19. doi: 10.1080/02652040500162840.
Entrapping probiotic bacteria in gels with ionic cross-linking is typically achieved with polysaccharides (alginate, pectin, carraghenan). In this study, whey proteins were used for this purpose by carrying out the Ca(2+)-induced gelation of pre-heated whey protein isolate (WPI). A Lactobacillus rhamnosus cell suspension was added in a denatured WPI solution in a 30 : 70 volume ratio. Gelation was carried out by extrusion of the cell suspension in a CaCl(2) solution. Beads of approximately 3 mm diameter were formed. The population in the beads was 8.0 x 10(8) cells g(-1). Entrapment efficiency in gel beads was 96%, with a survival level of 23%. Scanning electron microscopy of beads before freeze-drying showed a tight protein network containing encapsulated Lb. rhamnosus cells homogeneously distributed throughout the matrix. The survival to freeze-drying of the bead-entrapped cells was 41%. Viability of microentrapped cells in a dynamic gastro-intestinal (GI) model was studied and the results were compared to free cells freeze-dried in a milk-based cryoprotective solution, as well as in a pre-denatured WPI solution. Results showed that protein gelation provided protection against acidic conditions in the stomach after 90 min, as well as against bile after 30, 60 and 90 min in the duodenum. Moreover, the milk-based cryoprotective solution was equally effective after 90 min in the duodenum. It is concluded that the gelation of whey proteins induced by Ca(2+) ions can protect the cells against adverse conditions of the GI system. However, certain stages in the entrapment process, particularly extrusion in the solution of CaCl(2), still need to be optimized in order to reduce the mortality of the cells during gelation.
通过离子交联将益生菌包埋在凝胶中通常使用多糖（藻酸盐、果胶、角叉菜胶）来实现。在本研究中，通过对预热的乳清蛋白分离物（WPI）进行钙（Ca²⁺）诱导凝胶化，将乳清蛋白用于此目的。以30:70的体积比将鼠李糖乳杆菌细胞悬液添加到变性的WPI溶液中。通过将细胞悬液挤出到氯化钙（CaCl₂）溶液中来进行凝胶化。形成了直径约3毫米的珠子。珠子中的菌数为8.0×10⁸个细胞/克。凝胶珠中的包埋效率为96%，存活率为23%。冻干前珠子的扫描电子显微镜显示，紧密的蛋白质网络中含有均匀分布在整个基质中的包封鼠李糖乳杆菌细胞。包埋在珠子中的细胞冻干存活率为41%。研究了微包埋细胞在动态胃肠（GI）模型中的活力，并将结果与在基于牛奶的冷冻保护溶液以及预变性的WPI溶液中冻干的游离细胞进行了比较。结果表明，蛋白质凝胶化在90分钟后能保护细胞免受胃中酸性条件的影响，以及在十二指肠中30、60和90分钟后免受胆汁的影响。此外，基于牛奶的冷冻保护溶液在十二指肠中90分钟后同样有效。得出的结论是，Ca²⁺离子诱导的乳清蛋白凝胶化可以保护细胞免受胃肠系统不利条件的影响。然而，包埋过程中的某些阶段，特别是在CaCl₂溶液中的挤出，仍需要优化，以降低凝胶化过程中细胞的死亡率。
