Effect of sub-lethal heat stress on viability of Lacticaseibacillus casei N in spray-dried powders

Abstract

The potential of thermal adaptation enabling a probiotic Lacticaseibacillus casei N (N) to withstand heat stress and spray drying was investigated. Among the encapsulating agents used (maltodextrin, corn starch (CS), and acacia gum) for lactobacillus, CS had shown the highest survivability of 95.6% after spray drying. Further, the slurry prepared using L. casei (N), and CS as carrier material was subjected to sub-lethal heat stress at 45 and 50 °C for 60 min before spray drying. After spray drying, survivability was increased by 0.26 and 0.19 log in N + CS 45 and N + CS 50, respectively, compared to a control that was not treated to sub-lethal stress (N + CS). During storage studies for 90 days, the sub-lethal heat-stressed probiotic powders had shown better survivability at 4 °C. The survivability of L. casei (N) in spray-dried powders in simulated gastric fluid revealed that N + CS 45 had 3.06 log cycles higher survivability than N + CS. The SDS PAGE and FTIR analysis of intracellular proteins of heat-stressed L. casei (N) cells revealed overexpression of heat shock proteins indicating a change in protein structure. The study suggests that the sub-lethal heat stress before spray drying increases the viability of probiotic cultures, which have potential food applications.