Novel high-pressure thermal processing at industrial scale efficiently inactivates bacterial spores while minimises process-induced contaminants in acid and low-acid infant food.

Abstract

High-pressure thermal processing (HPTP) takes advantage of rapid and uniform compression heating and decompression cooling. However, its industrial implementation faces scale-up and operational challenges. In this study a novel insulated canister for a HPTP industrial equipment was validated assessing Geobacillus stearothermophilus spore inactivation and process-induced contaminants (hydroxymethylfurfural and acrylamide) formation in apple puree (pH 3.0), banana puree (pH 3.5) and vegetable and fish meal (pH 5.6), at varying pressures (200-600 MPa) and times (0-10 min). Product acidity impacted on spore inactivation. A 600 MPa pulse caused more than 6 log spore reduction in apple and banana puree, but only 1.2 ± 0.2 log in vegetable and fish meal, which required longer times to reduce 5 log, following a log-linear trend. HPTP spore inactivation with the insulated canister exceeded "botulinum cook" standards, highlighting its potential to efficiently sterilise low-acid foods. Pressure increase and acidity slightly promoted hydroxymethylfurfural formation in fruit puree (1.08 ± 0.14 ppm and 0.12 ± 0.04 ppm, in apple and banana, respectively) after 600 MPa pulse reaching 115 °C. Moreover, no acrylamide was formed in vegetable and fish meal (<13 μg/kg). The use of the novel insulated canister constitutes a step forward bringing the HPTP technology at industrial scale. Without heating the whole pressurisation fluid and equipment walls, the efficient rapid, uniform and adiabatic heating and cooling of food (by compression and decompression mechanisms) achieved with the insulated canister, makes HPTP technology a feasible alternative to conventional thermal technologies to inactivate bacterial spores, minimizing the process-induced contaminants formation and avoiding the food matrix overprocessing.