Optimal sterilization temperatures are defined as the processing temperatures which result in a minimum surface cook-value after achieving the desired degree of sterility. They were calculated as a function of product heating rate, surface heat transfer coefficient, initial food temperature, heating medium come-up-time, z-value for the quality factor and target Fo-value. Different one-dimensional heat transfer shapes were considered. Compared to the other variables, initial temperature and heating medium come-up-time had little influence on optimal processing temperature. Regression equations were developed relating optimal temperatures with all relevant variables.

Optimal sterilization temperatures for conduction heating foods considering finite surface heat transfer coefficients

A resurgence in interest examining thermal pasteurization technologies has been driven by demands for “cleaner” labeling and the need of organic and natural foods markets for suitable preventive measures to impede microbial growth and extend shelf life of minimally processed foods and ready-to-eat foods with a concomitant reduction in the use of chemical preservatives. This review describes the effects of thermal pasteurization on vegetable quality attributes including altering flavor and texture to improve consumer acceptability, stabilizing color, improving digestibility, palatability and retaining bioavailability of important nutrients, and bioactive compounds. Here, we provide kinetic parameters for inactivation of viral and bacterial pathogens and their surrogates and marker enzymes used to monitor process effectiveness in a variety of plant food items. Data on thermal processing protocols leading to higher retention and bioactivity are also presented. Thermal inactivation of foodborne viruses and pathogenic bacteria, specifically at lower pasteurization temperatures or via new technologies such as dielectric heating, can lead to greater retention of “fresh-like” properties.

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Predicting the Quality of Pasteurized Vegetables Using Kinetic Models: A Review.

Optimising the safety and quality of thermally processed packaged foods.

The effect of reel speed, can size, and percent air during steam and steam/air processing in a Steritort on the heating rate of tomato concentrate (an induced convection-heating product) was investigated A Taylor expansion equation, relating Ball process times with the above three variables, considering first order, second order, and interaction effects, was presented A correlation equation for the Nusselt number as a function of the Reynolds and Prandtl numbers, the can length over the diameter ratio, and the steam content was also presented Percent reduction in process lethality increased with increasing can size and air content, and decreasing reel speed and target lethality Increase in percent air in the steam/air mixture could be compensated by an increase of the rotational speed

EFFECT of STEAM/AIR MIXTURES ON THERMAL PROCESSING of an INDUCED CONVECTION-HEATING PRODUCT (TOMATO CONCENTRATE) IN A STERITORT

This chapter is concerned with the measurement and interpretation of heat penetration curves, obtained from temperature measurements inside the food in the container or package. It is the most important part of determining an adequate process for sterilizing or pasteurizing food products. However, because of the complex nature of food products, the number of different packages and the variety of methods of processing them, the interpretation of the data is often difficult. All thermally processed packaged foods require a validated process schedule which is traceable to heat penetration measurements. The methods of doing this and the treatment of the experimental data are outlined.

Heat Penetration in Packaged Foods

Effects of residual air were evaluated on the heating rates of a convectionheating product processed in a continuous rotary sterilizer. Heat penetration tests were conducted in a Steritort at various reel speeds (1-10 rpm) and air overpressures (0-69.0 kPa) using 211 × 300, 300 × 407 and 603 × 700 cans containing Washington white beans in brine. Sterilization times calculated by Ball's formula method were longer for test cans processed with overpressure than those processed with no overpressure. Maximum reduction in calculated lethality for 69.0 kPa air overpressure was 15.2% for 211 × 300 and 300 × 407 experiments and 49.4% for 603 × 700 experiments. For each can size and reel speed, average process time was a linear function of overpressure.

M. Gee

Papers

Effects of Steam/Air Mixtures on a Convection-Heating Product Processed in a Steritort