Optimisation of industrial-scale steam sterilisation and drying for improved microbial safety and quality of red pepper powder

Red pepper powder is widely used in various cuisines and food industries. Therefore, effective microbial reduction methods are essential to ensure product safety and quality. This study evaluated the microbial reduction efficiency of a newly developed industrial-scale steam steriliser for red pepper powder. The effects of sterilisation time, steam temperature, and steam injection quantity on microbial reduction were investigated. Sterilisation efficiency was assessed based on reductions in indicator microorganisms, including total aerobic bacteria and Enterobacteriaceae. Higher steam temperatures and longer sterilisation times significantly enhanced microbial reduction, with optimal conditions achieving up to a 4-log (99.99%) reduction in the total microbial count. Kinetic parameters, including process-specific D values and pseudo-z values, were determined to provide quantitative insights into microbial population resistance under different processing conditions. Additionally, variations in hot-air drying temperature affected the moisture content and colour of the red pepper powder. During drying, low temperatures (25–80 °C) resulted in insufficient moisture removal and noticeable colour changes, whereas higher temperatures (100–160 °C) better preserved the original colour while achieving effective moisture control. Crucially, the optimised steam sterilisation process increased the extractability of major pungent components (capsaicinoids) due to heat-induced structural relaxation of the plant matrix, while successfully preserving the profile of total volatile organic compounds (TVOC) without significant degradation. These findings demonstrate that steam sterilisation combined with optimised drying conditions effectively reduces microbial contamination while maintaining product quality. The results provide valuable guidance for optimising sterilisation parameters in industrial applications and improving safety and quality during red pepper powder production.