Pasteurization of dehydrated food powders with radio frequency heating
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Low-moisture foods with water activity (aw 0.6) associated Salmonella outbreaks have become a major food safety concern, which brought attention the food industry, government and scientific community to develop technology for its remediation. Current conventional decontamination methods for low -moisture foods including dehydrated vegetable powders and spices have not been widely accepted due to the public health concern or quality degradation. Radio frequency (RF) heating as an alternative novel technology provides a great chance for pasteurization of dehydrated vegetable powders and spices with reduced come-up time, which allows to design a faster heating process to inactivate Salmonella with minimized quality degradation in food products.However, the major challenge for developing an effective RF heating system for microbial inactivation is the non-uniform and unpredictable heating pattern. Thus, the focus of this research was on developing a strategy to improve heating uniformity by investigating the influence of multiple factors including dielectric properties (DP),moisture content, electrode gap and packaging material on the heating rates and uniformity in various low-moisture foods and assessing the effectiveness of RF heating pasteurization for Salmonella on the food powders were used corn flour, paprika, white pepper and cumin powder, and evaluate Enterococcus faecium NRRL B-2354 (E. faecium) as a surrogate for RF heating inactivation of Salmonella. DP values of various vegetable powders and spices were determined using a precision LCR meter and liquid test fixture at frequency ranging from 1 to 30 MHz.RF heating uniformity and temperature profiles of each sample as treated under a to RF heating system (27.12-MHz, 6-kW) were obtained with an infrared camera and data logger with a fiber optic sensor. Finally, the effectiveness of RF heating on pasteurization of Salmonella and its potential surrogate E. faecium was evaluated. In this study, RF heating can be used effectively to pasteurize corn flour, paprika and white pepper. Additionally, a combination of RF heating and post-freezing storage at -20°C for 48h helped to reduce survival of microorganisms, and E. faecium was found as a potential surrogate of Salmonella on the powders were used corn flour, paprika, white pepper and cumin powder to validate RF heating process.