Inactivation Kinectics For Pathogens In Red Pepper Powder Treated By Radio Frequency And Its Quality Study

Low-moisture food inactivation is a research hotspot in the world at present.Red pepper powder is a kind of low-moisture powder condiment,which is easy to cause microbial pollution during processing and transportation,including some pathogens(such as Salmonella,Bacillus cereus etc.),thus causing food safety problems.In this study,radio frequency,a new technology,its rapid and overall heating,high heating efficiency,easy process control and other advantages were used to study the effect of red pepper powder’s pathogen inactivation,establish red pepper powder inactivation kinetics model,and analyse its quality changes.The main contents and results are as follows:Firstly,the influence of the key parameters in the RF heating process on RF heating effect was studied,and the process parameters of RF heating treatment were determined.Including the gap between the parallel electrode plates,the best material placement between the electrode plates(vertical direction),and the initial a_w of different materials on the RF heating process.The results show that the higher the electrode gap is,the slower the RF heating rate is.When the material is in the middle of the electrode plate(vertical direction),the RF uniformity is the best.The RF heating rate increases with the initial a_w,but when the a_w increased to a certain degree(0.71),the heating rate would decrease.Secondly,two kinds of pathogenic bacteria(Salmonella and Bacillus cereus spores),which are easy to be polluted and cause food safety problems,were studied in this paper.The effects of different initial a_w on the bactericidal effect were studied,and the kinetics model of red pepper powder was established.The results showed that the bactericidal effect of Salmonella was increased first and then decreased with the increase of a_w,and the bactericidal effect was the best when the initial a_w of red pepper powder was 0.71.The bactericidal effect of Bacillus cereus spore increased with the increase of a_w.From the results of inactivation kinetic model,Weibull model could predict the change of Salmonella in different a_w red pepper powder by RF inactivation.The parameter b showed a trend of increasing first and then decreasing with the increase of a_w,while the parameter n had no obvious linear relationship.Bacillus cereus spore had good fit in the three models(Linear,Weibull and Log-logistic models),but the optimal model was different under different temperature and a_w.The linear model was the best when the a_w was 0.74,and the Weibull model had the best fit at the higher temperature(80,90°C).Similarly,the parameter b increases with the increase of a_w was the first increase and then decrease the trend,while the parameter n showed a negative linear correlation.Finally,the effects of different RF treatment conditions on the quality of red pepper powder were studied,and the effects on the pepper flavor and color were studied.The results showed that the capsaicinoids had good stability and were insensitive to RF treatment.RF treatment(70-90°C,0-5min)did not affect capsaicin,dihydrocapsaicin and capsaicin(P>0.05),and the effect of different initial a_w was not significant.The content of red pigment in capsicum with the a_w was not changed after RF treatment.When the a_w of red pepper powder was low(0.40),the content of capsanthin decreased obviously after RF treatment,but there was no significant change when a_w was high.