Effects of micronization on viability and thermotolerance of probiotic freeze-dried cultures

Abstract

Abstract Three strains of probiotic freeze-dried bacteria, Bifidobacterium breve R070 (BB R070), Bifidobacterium longum R023 (BL R023), and Lactobacillus acidophilus R335 (LA R335), were micronized using a spiral jet mill as grinding system, in order to decrease the powder particle size for incorporation in multiphase low-diameter microcapsules produced by emulsification and spray-drying. The effects of grind air pressure (1, 2, 4 or 5.5 bar) and product feed rate (150 or 300 g h −1 ) on powder particle-size distribution and bacterial viability were evaluated. The D ( ν , 0.9) of the micronized powder was found to be only affected by grind air pressure ( P −1 was selected as the least destructive treatment (survival rate of 25.5±5.2%) to produce powders of probiotic freeze-dried cultures with particle-size distribution suitable for the microencapsulation technology ( D ( ν , 0.9) E a , D 45°C , D 65°C , D 80°C ). Results indicated that BL R023 displayed intrinsic low heat resistance whereas particle-size reduction dramatically increased the thermosensitivity of BB R070. Micronization is an effective way of reducing powder particle size of freeze-dried bacterial cultures for subsequent use in cell immobilization applications with low heat treatment.