Thermal inactivation of Salmonella Enteritidis PT30 in ground cinnamon as influenced by water activity and temperature

Abstract

Reported outbreaks and recalls related to spices, including an on-going recall of cinnamon involved apple chips, reveal a need to understand thermal inactivation of Salmonella in spices. Recent studies have documented quantitative relationships between water activity (aw) and thermal resistance of Salmonella in a wide range of low-moisture foods. Such quantitative data are useful in developing effective thermal treatments. However, the influence of aw on thermal inactivation of Salmonella in spices has not been systematically studied. Cinnamon is known for its antimicrobial effect on pathogenic bacteria. We hypothesized that the synergetic effect of heat and the natural antimicrobial compounds in cinnamon would reduce the intensity of thermal treatments for cinnamon compared to that for other low-moisture foods. This study investigated the thermal resistance of Salmonella Enteritidis PT 30 in ground cinnamon at three inactivation temperatures (70, 75 and 80 °C). The log10D-values of S. Enteritidis PT 30 in ground cinnamon decreased linearly with increasing aw and treatment temperature. By comparing the log10D-values obtained in ground cinnamon with the reported log10D80°C-values of S. Enteritidis PT 30 in other low-moisture foods, we found that the thermal treatments at 70 °C for S. Enteritidis PT 30 in cinnamon powder was roughly equivalent to the treatments at 80 °C for the same bacterial strain in other low-moisture foods, such as wheat flour and egg powders. Thus, milder thermal treatments can be used for the control of Salmonella in cinnamon powder, and perhaps other spices or herbs that contain antimicrobial compounds, for better retention of product quality.