The decontamination of industrial casein and milk powder by irradiation

摘要

The efficacy of gamma radiation decontamination of industrial casein,a milk protein utilized as a component of many food and non-food products has been studied.Low-fat milk powder was also included with a purpose to study the microflora survival in protein-rich materials.Microbial analysis of the samples prior to irradiation showed that the initial total viable count was higher than 6.0 log cfu g~(-1)in both casein and milk powders.The contamination of casein with moulds and yeasts was found to be equal to 3.56 log cfu g~(-1).The counts of conforms have not exceeded the value of 2.48 log cfu g~(-1).Radiation processing of casein and milk powder has substantially reduced the microbial population of all samples.The dose of 5 kGy was sufficient to reduce the total microflora and coliforms counts to the level permitted for food products.Survivals of microorganisms were analyzed by the generalized exponential equation,SF=exp[-D/D_o)~(alpha)].Values of an exponent,a,standing for the dispersion parameter,were equal to 0.65 and 0.70 for microorganisms contaminating casein and milk powders,respectively.The numerical value of the dispersion parameter alpha<1 indicates the concave dependence of a logarithm of surviving fraction versus radiation dose.No difference in microflora survival in irradiated samples tested immediately and in samples stored for 1-month after irradiation has been noticed.