Infrared Thermal Image Processing Technique for Evaluating Superheated Steam as a Dry Sanitation Method

Abstract

AbstractThe objectives of this study were to develop a thermal image analysis method for assessing the surface temperature of stainless steel (30 cm × 30 cm) during pilot-scale superheated steam sanitation and evaluate the sanitation efficacy based on the inactivation of Enterococcus faecium. An infrared camera, calibrated to a root-mean-square error (RMSE) of 1.4 °C within a range of 25 °C and 250 °C, was utilized. The results showed that the surface temperature at the impingement point decreased linearly from 245.6 ± 3.2 to 157.6 ± 1.7 °C as the nozzle-to-surface distance was increased from 2 to 5 cm. Furthermore, at a 2 cm nozzle-to-surface distance, temperatures swiftly dropped from 245.6 ± 3.2 to 95.8 ± 6.0 °C as the radial distance increased from 0 to 10 cm. In the stagnation region (0–1 cm radial distance), where the steam jet directly contacts the surface, the time required to achieve a 3-log reduction of E. faecium was reduced from 3 to 1 min as the nozzle-to-surface distance decreased from 5 to 2 cm. The efficacy of superheated steam sanitation was further evaluated under practical sweeping conditions, demonstrating a 2.7 ± 0.4 log reduction of E. faecium on a 900 cm2 stainless steel surface within 10 min. This study thus highlights the potential use of thermal image analysis for optimizing superheated steam sanitation processes, particularly in dry food processing environments.