Developing Pasteurization Technology For Red Pepper Powder Using Radio Frequency Heating

Red pepper powder is an indispensable condiment for daily cooking and food processing.It can not only enable the unique flavor for food,but also endow food with bright color.Recently,with the rapid development of the seasoning convenience in food industry,the demand and trade volume of red pepper powder have increasingly expanded.The production and processing of red pepper powder have entered a stage of rapid development,which becomes a new economic growth point.However,the food safety problem of red pepper powder caused by food-borne pathogens restricts the development of the red pepper powder industry.Therefore,ensuring effectively the safety and security of red pepper powder has become one of its research hotspots.In this study,the pasteurization research of red pepper powder was carried out based on the radio frequency(RF)heating system.At first,the relationship among different factors including powder particle size,bacterial strain and temperature on the average Log reductions of pathogens in red pepper powder was investigated using the heating block system,and then the powder particle size and bacterial strain were determined as the most heat-resistant conditions.In addition,the influence of particle size of red pepper powder on its thermal characteristics was discussed.The thermal inactivation kinetics of the selected pathogens in red pepper powder at three a_w levels with four temperatures were established.At last,the hot air assisted-RF heating system was used to develop and verify the pasteurization process of red pepper powder,and then compared the quality changes of red pepper powder before and after RF treatment.The main research contents and results are as follows:(1)Effects of three bacterial strains and particle size on the average Log reductions of pathogens were analyzed based on the orthogonal experiment design method.The results showed that E.coli ATCC 25922 had the lowest reductions at 0.45-1.00 mm red pepper powder,that is,the non-pathogenic substitute E.coli ATCC 25922 had higher heat resistance than that of the other two strains.The heat resistance of microorganisms increased with the increase of the particle size of red pepper powder.The thermal characteristics of three particle sizes of red pepper powder were measured.The results showed that the difference in heat resistance of microorganisms caused by different particle sizes of red pepper powder was not caused by its thermal characteristics.(2)The microbial inactivation curve was fitted both by the first-order kinetic and Weibull models to obtain thermal inactivation kinetic parameters,in which the lower a_w level and temperature resulted in larger D-values.Mafart's modified Bigelow model combined with primary models provided acceptable predictions of microbial inactivation performance under the given test conditions.E.coli ATCC 25922 at the higher a_w level tends to show higher inactivation rate at relatively low temperatures with red pepper powder of fixed particle sizes.(3)An effective hot air-assisted RF pasteurizations process for the fixed particle size of red pepper powder was developed.The hot air(70?)assisted RF treatments with the electrode gap of 180 mm for 40 min were used for pasteurizing the red pepper powder samples of 1.0 kg with moisture content(MC)of 12.38%(w.b.)at particle size of 0.45-1.00mm to achieve more than 4-Log reductions,and then heat intermittently with the electrode gap of 190 mm for 20 min used for drying to reduce the moisture content of red pepper powder to 9.00%(w.b.).The detection of 4 quality indexes(moisture content,water activity,color,and total natural coloring matter content)of red pepper powder after RF treatment showed that RF pasteurization treatment had no significant effect on the quality of red pepper powder.