Inactivation of Salmonella Enteritidis PT30 on black peppercorns in thermal treatments with controlled relative humidities.

Traditional method utilizes steam to pasteurize low-moisture ingredients like black peppercorns and almonds. Exposure to steam results in direct condensation on the product, unfavorable for a broader range of food ingredients such as dried herbs, fruits, and ground materials. Recent studies on the thermal inactivation of Salmonella in low-moisture foods suggest that the relative humidity in treatment chambers is an important factor, besides temperature, that determines the death rate of bacteria.

Desiccation in oil protects bacteria in thermal processing.

Edible oils have long been considered to have a protective effect on bacteria from thermal inactivation, but the mechanism for this effect remains unclear. Our recent study suggests that the water activity (a) of oil decreases exponentially with increasing temperature. Therefore, in thermal processing, the a of the bacteria inside oil may also decrease making the bacteria more resistant to heat.