Effect of heat adaptation and pH adjustment on the survival of spray-dried Lactobacillus paracasei SNP2

Abstract

Purpose The purpose of this paper is to study the effect of heat adaptation, pH adjustment, and the combination pretreatments to the resistance of Lactobacillus paracasei SNP2 in heat shock and spray drying. Design/methodology/approach Sub-lethal and lethal temperature range of L. paracasei SNP2 was determined by enumeration of cell survival after incubation at 37-55°C for 30 min. A certain temperature from sub-lethal range was selected for heat adaptation. Heat adaptation (H), pH adjustment (pH), and combination of pretreatments (pH-H) were applied prior to heat shock and spray drying. Findings The selected condition for heat adaptation and heat shock is 44°C, 30 min and 55°C, 15 min, respectively, based on the sub-lethal and lethal temperature range. By heat shock, cells in the whey-sucrose medium showed cell death of 2.05 log cycles, lower than cell death in the MRS medium of 4.84 log cycles. The pretreatments showed slight increase of heat resistance in cell grown in whey sucrose. The effect of H, pH, and pH-H pretreatments highly increase heat resistance of cell grown in MRS indicated by cell death of 4.27, 3.79, and 2.43 log cycles, respectively, which is much lower than control. The pretreatments showed no significant effect to L. paracasei SNP2 survival to spray drying. Originality/value This is the first study of L. paracasei SNP2 resistance to heat shock and spray drying. This paper also enriches information about application of whey sucrose as a growth medium and a heating medium.