Compression Heating and Temperature Control for High-Pressure Destruction of Bacterial Spores: An Experimental Method for Kinetics Evaluation

Abstract

High-pressure (HP) processing is considered as an alternative technique for thermal sterilization of high quality foods. Adiabatic compression during pressurization allows for quick increase in temperature of food products, which is reversed when the pressure is released, thereby providing rapid heating and cooling conditions and hence short process times. However, during the pressure holding time, the product experiences a temperature drop as a result of heat loss to the vessel. The temperature variation during the process and the synergistic effect of temperature and pressure make it difficult to get the required accurate data on microbial spore destruction kinetics. In this study, a polyoxymethylene (POM)-insulated chamber was evaluated for temperature control in the test sample during pressure treatment. Temperature variations in the HP system were measured in milk test samples inside the POM insulator and pressure medium in the HP vessel under various conditions of pressures (500-900 MPa) and initial temperatures (20-80°C). Results demonstrated that the POM chamber had good thermal-insulation characteristics under pressure and was able to maintain stable operating conditions for microbial spore destruction kinetics. Based on the measured adiabatic temperature change, the required initial temperatures for the test sample and pressure medium were generated as a quadratic function of pressure and temperature. The setup was then verified for pressure inactivation of Clostridium sporogenes (PA 3679) spores in ultra-heattreated milk. The better temperature stability of test samples during treatment provided a means to gather accurate data on HP destruction kinetics of the microbial spores.

Clostridium sporogenes-ATCC 7955 Spore Destruction Kinetics in Milk Under High Pressure and Elevated Temperature Treatment Conditions

“…1). Full details of this chamber and its performance are given in Shao et al (2008). The insulator was assembled in pressure vessel for delaying heating transfer from sample tubes to pressure vessel during high-pressure processing.…”

“…Regression models were established to compute the processing temperature as a function of initial sample temperature (T i ; 20°C≤T i ≤80°C) and pressure (P; megapascal; Shao et al 2008). The conditions employed in this study are detailed in Table 1.…”

“…High-pressure processing has been recognized as novel and innovative preservation method as an alternative to the high-temperature short-time commercial sterilization of low-acid foods (LAFs) because high pressure when combined with moderately elevated temperatures can inactivate highly resistant bacterial spores (Sale et al 1970;Seyderhelm and Knorr 1992;Mills et al 1998;Shao et al 2008;Zhu et al 2008). Adiabatic compression caused by pressurization results in quick heating of the product to process temperatures, and the subsequent decompression results in its rapid cooling.…”

Reaction Kinetics at High Pressure and Temperature: Effects on Milk Flavor Volatiles and on Chemical Compounds with Nutritional and Safety Importance in Several Foods

“…An emerging and particularly innovative conservation procedure, Pressure-Assisted Thermal Processing (PATP), applicable to almost all processed foods, could facilitate meeting the demand for more healthy, nutritious, varied, and convenient processed food. PATP is based on the combined application of high pressure and high temperature, typically in excess of 600 MPa and 100°C (Shao et al 2010). PATP promises to yield shelfstable foods of high quality and with reduced losses of constituents with desirable health benefits to consumers (Pérez Lamela and Torres 2008a, b;Torres et al 2009b).…”

Improvement in Texture of Pressure-Assisted Thermally Processed Carrots by Combined Pretreatment using Response Surface Methodology

“…Uniform compression heating during pressurization and rapid cooling on depressurization helps to reduce the severity of thermal effects encountered with conventional thermal processing (Rasanayagam et al 2003;Shao et al 2008). The technology reportedly reduces process time and preserves food quality.…”