Survival of freeze-dried microcapsules of α-galactosidase producing probiotics in a soy bar matrix

Soy oligosaccharides, mainly alpha-galactosides, are prevalently present in soy protein products, and can result in unfavorable digestive effects when consumed. The aim of this research was to investigate the efficiency of alpha-galactoside reduction by probiotic bacterial hydrolysis and if such bacteria could be maintained in a high number in a soy protein product in a microencapsulated and freeze-dried form. The probiotic bacterium, Lactobacillus acidophilus LA-2, when induced by raffinose, exhibited a high level of alpha-galactosidase activity at 5.0 U/mg. To preserve probiotics with high viability, cells were microencapsulated and freeze-dried. Optimization of microencapsulation presented that a combination of kappa-carrageenan and inulin at a proportion of 1.9:0.1 (w:w) as capsule wall materials, significantly retained the viability of the probiotics through freeze-drying (P < 0.05). Scanning electron microscopic images confirmed that the morphology of the microcapsules was well preserved after freeze-drying. Upon incorporation into soy protein bars, the freeze-dried microcapsules of L acidophilus LA-2 remained in high numbers throughout 14 weeks of storage at 4 degrees C. Results of this work with the support of other studies on microencapsulation benefits indicate a promising use of freeze-dried alpha-galactosidase positive microencapsulated probiotics in a soy food. (C) 2011 Elsevier Ltd. All rights reserved.