Modification of a Grain Moisture Conditioner into a Vacuum Steam Pasteurizer

Abstract

Eliminating microbes in low-moisture foods (LMFs) is challenging because this requires the preservation of their raw quality during pasteurization. Vacuum steam pasteurization (VSP) has been shown to be effective in reducing microbes while maintaining food quality. These studies were conducted at a laboratory scale where issues such as steam distribution, penetration, and condensation are not a concern, but in larger samples, these are of primary concern. Hence, this study repurposes a pilot-scale grain moisture conditioner (GMC) into a VSP system with the aim of replicating the lab-scale conditions in larger-scale applications. The modification entailed a series of design alterations, conducting a structural analysis of the conditioning chamber, creating a vacuum environment, ensuring uniform steam distribution, and designing and adding a preheater and a cooling system. Performance tests confirmed that the adapted system replicates the VSP’s lab-scale functionality. The results demonstrated that the VSP system can preheat to beyond 40 °C and achieve an absolute pressure of 11.7 kPa at 85 °C with a 344.7 Pa pressure increase per minute. Furthermore, steam distribution inside the chamber showed no significant variations, and rapid steam evacuation and chamber cooling could be performed simultaneously. The success of these modifications will be used in future experiments.