Abstract:
Consumer demand for healthier, fresher and tastier food products has boosted the development and application of non-thermal technologies. High-Pressure Processing (HPP) consists of the application of pressures between 100-1000 MPa to foods for microbial inactivation. HPP has been commercially applied to pasteurize fruit juices and offers significant benefits in terms of the preservation of bioactive constituents and the maintenance of the original organoleptic properties. The design of a food pasteurization process normally requires the use of a reference target, which is often the most resistant spoilage microorganism or enzyme. Alicyclobacillus acidoterrestris spore has been suggested as a reference in the design of pasteurization for high-acid shelf-stable fruit products, due to its thermal resistance and spoilage incidents registered in fruit juices. In this research, HPP (600 MPa) combined with mild heat (35°C-65°C) were used to inactivate the spores of A. acidoterrestris in malt extract broth (MEB) adjusted to different soluble solids content (10-30°Brix). The baroprotective effect caused by the soluble solids was observed, and inactivation curves were modelled using the first-order kinetics and non-linear models (Weibull, modified Gompertz and Log-Logistic). From the first-order kinetics, for 10°Brix, D35°C = 38.08 min, D45°C = 10.32 min, D55°C = 4.17 min and zT-value = 20.82°C. For 20°Brix, D45°C = 21.63 min, D55°C = 7.59 min, D65°C = 2.18 min and zTvalue = 20.07 °C. For 30°Brix, D45°C = 32.26 min, D55°C = 13.71 min, D65°C = 3.76 min and zT-value = 21.43°C. The z-value for the effect of soluble solids on DT-values was also estimated. The z-values for 45 and 55°C were respectively 40.42 and 38.70°Brix. The results demonstrated that a combined HPP-thermal process was an effective alternative to conventional thermal processing for the inactivation of A. acidoterrestris spores up to 30°Brix solids content. The results obtained with broth adjusted to different ˚Brix values were well validated with commercial juices/concentrates, especially up to 10 min processing times. The benefits observed with HPP-thermal technology were evident, since it allowed the use of lower temperatures (30-40˚C less) than the conventional thermal pasteurization for the same microbial inactivation, which results in healthier, fresher and tastier fruit juice/concentrate.
