Encapsulation of bifidobacteria in whey protein-based microcapsules and survival in simulated gastrointestinal conditions and in yoghurt

Abstract

Abstract Bifidobacterium breve R070 (BB R070) and Bifidobacterium longum R023 (BL R023) were encapsulated as freeze-dried or fresh cultures in water-insoluble food-grade microcapsules produced by emulsion and/or spray-drying, using milk fat and/or denatured whey proteins as immobilization material. The encapsulation yield differed significantly according to the method and the strain used. Dispersion of fresh cells in heat-treated whey protein suspension followed by spray-drying was the least destructive immobilization technique tested, with a survival rate of 25.7±0.1% and 1.4±0.2% for BB R070 and BL R023, respectively. Viable counts of BB R070 cells entrapped in whey protein microcapsules using this method were significantly higher than those of free cells after 28 days in yoghurt stored at 4°C (+2.6 log cycles), and after sequential exposure to simulated gastric and intestinal juices (+2.7 log cycles). In contrast, no protective effect of encapsulation was observed with BL R023. Immobilization of probiotic cultures in whey protein-based microcapsules can increase cell survival when subjected to extreme conditions, making this approach potentially useful for delivery of viable bacteria to the gastrointestinal tract of humans via dairy fermented products. However, technological properties of the strains, and particularly heat resistance, should be taken into consideration for spray-dry encapsulation of sensitive microorganisms.