High Pressure Inactivation of Lactobacillus plantarum in a Model Beer System

ABSTRACT: The effects of hop extract and ethanol on growth, high pressure inactivation, and survival of Lactobacillus plantarum were determined in model beer. Corresponding to the beer spoiling ability of this strain, levels of hops and ethanol typical for beer did not inhibit growth. Pressure death time curves determined at 300 MPa were described by an empirical model taking into account the sigmoid shape of survivor curves, sublethal injury, and the presence of baroresistant cells. Ethanol (5 and 10%) enhanced pressure effects on L. plantarum whereas hop extract (50 and 100 ppm) was less effective. In contrast, hop extracts killed pressurized cells during subsequent storage in beer but ethanol did not.