Influence of Superheated Steam Temperature and Moisture Exchange on the Inactivation of Geobacillus stearothermophilus  Spores in Wheat Flour‑Coated Surfaces by Park et. al..

Food and Bioprocess Technology, Springer, 2022

Sanitation in dry food processing environments is a major challenge for the industry. The influence of superheated steam
(SH) temperatures (125 to 250 °C) on the inactivation of spores on selected coupon surfaces (stainless steel, rubber, and
concrete) coated with wheat flour as a model food soil residue was investigated using a bench scale superheating apparatus.
Wheat flour inoculated with Geobacillus stearothermophilus (7.62 ± 0.12 log CFU/g) coated on the coupon surfaces served
as the model food residue. Among the surfaces tested, temperature of concrete increased faster [time constant (τ) < 89.0
s] than that of stainless steel (τ < 173.6 s). As a consequence, wheat flour coated on concrete dehydrated faster [moisture
diffusivity (Dm) > 1.17 × 10−4 mm2/s] than those on the stainless steel (Dm > 0.76 × 10−4 mm2/s). Hence, Geobacillus
stearothermophilus spores suspended on stainless steel were inactivated faster than that of concrete and rubber (p < 0.05).
The time required for a 5-log reduction at 250 °C were 180s and 240s, on stainless steel and concrete surfaces, respectively.
A mathematical model that considered surface temperature, food residue moisture content, and SH inversion temperature
adequately described spore inactivation during SH treatment.