High pressure inactivation of Lactobacillus plantarum in a model beer system

The effects of hop extract and ethanol on growth, high pressure inactivatio n, and survival of Lactobacillus plantarum were determined in model beer. C orresponding to the beer spoiling ability of this strain, levels of hops an d ethanol typical for beer did not inhibit growth. Pressure death time curv es determined at 300 MPa were described by an empirical model taking into a ccount the sigmoid shape of survivor curves, sublethal injury, and the pres ence 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.