Alicyclobacillus acidoterrestris spore inactivation by high pressure combined with mild heat: Modeling the effects of temperature and soluble solids

Abstract

High pressure processing (HPP) comprises the application of pressures between 100 and 1000 MPa to foods for microbial inactivation and food preservation. HPP has been commercially applied to pasteurize fruit juices with the advantage of retaining its bioactive constituents and original organoleptic properties. Alicyclobacillus acidoterrestris has been suggested as a reference in the design of pasteurization for high-acid fruit products, due to spore resistance and spoilage incidents in fruit juices. In this study, A. acidoterrestris spore inactivation by 600 MPa combined with mild heat (35–65 °C) in malt extract broth adjusted to 10, 20 and 30 °Brix was carried out and the inactivation was modeled. The soluble solids increased the resistance of the spores to 600 MPa-thermal process, while the temperature decreased its resistance. Although the nonlinear Weibull model gave better fittings, the first-order kinetic parameters were also determined. For example for 600 MPa at 55 °C D10°Brix = 4.2 min, D20°Brix = 7.6 min, D30°Brix = 13.7 min, and zT-values were 20–21 °C. The z-values for the effect of soluble solids on DT-values were 39–40 °Brix for 45 and 55 °C 600 MPa HPP. The results obtained with broth were validated with fruit juices and concentrates. The combination of HPP with heat was an effective alternative to conventional thermal processing for the inactivation of A. acidoterrestris spores in juices up to 30 °Brix, allowing the use of less 30–40 °C of temperature for the same microbial inactivation, which potentially results in more nutritious, fresher and tastier juices/concentrates.