title: Ultra high pressure homogenization (UHPH) inactivation of Bacillus amyloliquefaciens spores in phosphate buffered saline (PBS) and milk.
abstract: Ultra high pressure homogenization (UHPH) opens up new areas for dynamic high pressure assisted thermal sterilization of liquids. Bacillus amyloliquefaciens spores are resistant to high isostatic pressure and temperature and were suggested as potential surrogate for high pressure thermal sterilization validation. B. amyloliquefaciens spores suspended in PBS buffer (0.01 M, pH 7.0), low fat milk (1.5%, pH 6.7), and whole milk (3.5%, pH 6.7) at initial concentration of ~10(6) CFU/mL were subjected to UHPH treatments at 200, 300, and 350 MPa with an inlet temperature at ~80°C. Thermal inactivation kinetics of B. amyloliquefaciens spores in PBS and milk were assessed with thin wall glass capillaries and modeled using first-order and Weibull models. The residence time during UHPH treatments was estimated to determine the contribution of temperature to spore inactivation by UHPH. No sublethal injury was detected after UHPH treatments using sodium chloride as selective component in the nutrient agar medium. The inactivation profiles of spores in PBS buffer and milk were compared and fat provided no clear protective effect for spores against treatments. Treatment at 200 MPa with valve temperatures lower than 125°C caused no reduction of spores. A reduction of 3.5 log10CFU/mL of B. amyloliquefaciens spores was achieved by treatment at 350 MPa with a valve temperature higher than 150°C. The modeled thermal inactivation and observed inactivation during UHPH treatments suggest that temperature could be the main lethal effect driving inactivation.
authors.affiliation: College of Food Science and Nutritional Engineering, China Agricultural University Beijing, China ; National Engineering Research Center for Fruits and Vegetables Processing Beijing, China ; Key Laboratory of Fruits and Vegetables Processing, Ministry of Agriculture Beijing, China ; German Institute of Food Technologies Quakenbrück, Germany.
authors.forename: Peng
authors.initials: P
authors.lastname: Dong
authors.affiliation: German Institute of Food Technologies Quakenbrück, Germany ; Institute of Food Chemistry, Leibniz Universität Hannover Hannover, Germany.
authors.forename: Erika S
authors.initials: ES
authors.lastname: Georget
authors.affiliation: German Institute of Food Technologies Quakenbrück, Germany.
authors.forename: Kemal
authors.initials: K
authors.lastname: Aganovic
authors.affiliation: German Institute of Food Technologies Quakenbrück, Germany.
authors.forename: Volker
authors.initials: V
authors.lastname: Heinz
authors.affiliation: German Institute of Food Technologies Quakenbrück, Germany.
authors.forename: Alexander
authors.initials: A
authors.lastname: Mathys
keywords: Bacillus amyloliquefaciens; bacterial spore; fat content; inactivation; milk; ultra high pressure homogenization