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Micro-encapsulation of probiotic bacteria with alginate-starch as a dairy food delivery system |
K. KAILASAPATHY, G. Godward, and A. Talwalkar. Centre for Advanced Food Research, University of Western Sydney, Locked Bag 1797, South Penrith Distribution Centre, Richmond, NSW 1797, Australia To exert positive health effects probiotic bacteria incorporated into foods must be able to survive product shelf life, transit through gastro-intestinal tract and establish in sufficient numbers. Several studies however, have reported that these bacteria did not survive in high enough numbers when incorporated into dairy products such as yoghurt. The objective was to ensure that probiotic bacteria are able to withstand conditions of product shelf life and transit through the gastro-intestinal tract. The bacterial cells were physically protected with a food-grade gum such as alginate separating the bacteria from the environment. In this study, a practical method of micro-encapsulation of bacterial cells with alginate and Hi-MaizeTM starch was developed and tested. Micro-encapsulation followed by freeze drying of the probiotic bacterial cells ensured a smaller log reduction in viability of cells in yoghurt than free, freshly encapsulated and co-encapsulated freeze-dried cells. However, with cheddar cheese, it was found that free probiotic cells survived better than encapsulated cells, probably due to build up of bacterial metabolic end products such as organic acids within the capsule. Although encapsulation of L. acidophilus 2401, B. infantis 1912, L. acidophilus 910 and B. lactis 920 caused the viability to decrease (by almost two log cycles), it did not cause the cell viability to decrease below the recommended level of 1 million CFU/g of food product. This study also demonstrated that free probiotic bacterial cells are able to survive well in ice cream due to the protection given by higher amount of solids and fat in the product. Micro-encapsulation also served as a protective mechanism against oxygen toxicity in B. lactis 920. This encapsulation method can enhance the survival of probiotic bacterial cells in dairy products during their shelf life and has the potential to prevent cell death during transit through the gastro-intestinal tract.
Session 73, Dairy Foods: Probiotics and bioactive components in milk
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