Transforming Raw Milk into Safe Milk Using Electron Beam Processing

Introduction: Raw milk consumption is increasing, and illnesses associated with raw milk are also increasing.  Raw milk, though sterile in the udder, is a host to a vast microflora of bacteria, including pathogens. 

Purpose: We hypothesize that electron beam (eBeam) processing, a non-thermal food processing technology, is suitable for eliminating microbial pathogens in raw milk without detrimentally affecting nutrient content or sensory attributes. 

Methods: Bioburden reduction analysis was conducted, using non-selective agar to enumerate raw and eBeam pasteurized milk irradiated at 1.0k Gy and 2.0k Gy. Pathogen reduction analysis was accomplished by inoculating raw milk with C. burnetii and overnight cultures of S. aureus, E. coli O157:H7, C. jejuni, and L. monocytogenes to determine the D-10 values of each pathogen.  Nutritional analysis targeting calcium and vitamins B₂ and B₁₂was performed, and GC-olfactometry was used to perform aroma analysis. 

Results: The D-10 values for the pathogenic organisms was found to range between 74.87 Gy to 156.26 Gy, with L. monocytogenes being the most resistant pathogen. Processing raw milk at 1.0k Gy achieved between 4- and 5-log reduction of the natural bioburden.  With the exception of vitamin B₂, there was no significant difference in the nutrient content and aroma profiles of the raw milk and eBeam milk processed at 1.0 and 2.0 kGy. 

Significance: Current heat pasteurization standards for milk are designed to achieve a 6-log reduction of C. burnetii, and based upon the D-10 analysis of the target pathogens and the empirical data from the bioburden reduction studies, it appears that 2.0 kGy is effective at pasteurizing raw milk without affecting major milk nutrients or aroma profiles. Overall, these results point to the value of eBeam technology to meet the needs of consumer demand for raw milk while assuring the microbiological and public health safety of such non-thermally pasteurized milk.