Pressure-induced thermotolerance of Lactobacillus rhamnosus GG

Non-lethal high pressure treatment was evaluated regarding its potential of inducing heat resistance in Lactobacillus rhamnosus GG. Pressure pre-treated cells (at 100 MPa and 37 degreesC for 10 min) showed higher survivability than untreated ones when both were heat treated at 60 degreesC. Upon exposure to this lethal temperature for 5 min, cells survived better by 1.5 log-cycles in comparison to control group, when they were previously pressure treated at 100 MPa and 37 degreesC for 10 min. Apparently, only short-time heat resistance was positively affected by such pressure pre-conditioning step since at prolonged holding time at 60 degreesC (more than 7 min), no significant differences regarding the inactivation rate was observed. Various pressures (100-200 MPa), temperatures (37-50 degreesC), and holding times (5-10 min) were systematically investigated. The findings can serve as indications towards optimizing production of probiotic starter cultures using spray-drying. (C) 2003 Elsevier Ltd. All rights reserved.