Effect of heating rates on thermal destruction kinetics of Escherichia coli ATCC25922 in mashed potato and the associated changes in product color

In this study, the influence of heating rate on thermal inactivation kinetics of Escherichia coli ATCC 25922 in mashed potato and the associated changes in product color was evaluated. Five heating rates (0.1, 0.5, 1.0, 5.0 and 10.0 °C/min), three final temperatures (55, 57 and 60 °C) and five holding times (0, 5, 10, 30 and 60 min) were precisely controlled by a unique heating block system. Results showed that the slower heating rates (<1.0 °C/min) gave significantly higher D-values presumably attributable to heat-adaption during slow heating, and had a more detrimental effect on the color change. L∗ values decreased while a∗ values increased at lower heating rates to reach the target temperature and subsequent holding time. High correlation between microbial lethality and L* & a* values suggested that color change during thermal process could be used as an indicator not only for food quality change but also for the microbial inactivation (food safety). Therefore, heating rates during thermal treatment could have a significant effect on thermo-tolerance of surviving microorganisms and product quality. Results of this study could be useful for evaluation and optimization of thermal pasteurization.