Modeling the effect of gamma-irradiation on reducing total bacterial populations in gochujang intended for consumption by astronauts in space programs

Abstract

This study modeled the effect of gamma-irradiation on reducing bacterial populations in space gochujang (Korean red pepper paste). The gochujang samples were gamma-irradiated at 0, 5, 10, 15, and 20 kGy, and stored under accelerated storage condition (35A degrees C for 10 days). During storage, total bacterial populations in gochujang samples were enumerated on plate count agar (PCA) on day 0, 1, 3, 5, 7, and 10. To calculate maximum specific growth rate (A mu(max); log CFU/g/day), lag phase duration (day), low asymptote (Y (0); log CFU/g), upper asymptote (Y (max); log CFU/g), and surviving cell counts recovered with PCA were fitted to the Baranyi equation. The parameters then were further expressed as a function of irradiation dose. Total bacterial populations in gochujang were decreased to below detection limit (1 log CFU/g) after irradiation (5-20 kGy). The samples irradiated at 5, 10, and 15 kGy then had bacterial cell recovery, but no growth was observed in 20 kGy irradiated samples during accelerated storage. After validation of models, acceptable model performances (B factor=1.15, A factor=1.29, RMSE=1.044, R (2)=0.862) were observed. These results indicate that the developed models may be useful in predicting irradiation doses to produce space gochujang.