The objectives are to assess the efficacy of low penetration [NMT 20mm] and low dosage [< 1.0 kGy surface dose] E-beam irradiation to reduce levels of E. coli O157:H7 on a large chilled-beef surface and to evaluate the effect of the treatment on the sensory properties of the product.
Untrimmed, unchilled beef navels will be removed from hot carcasses immediately after the post final intervention steam pasteurization process step. The excised navels will be inoculated with an E. coli O157:H7 strain (ATCC 43888) that has been deleted for all Shiga toxins. The beef navels will be inoculated at high and low levels and marked into areas of control and treatment. The treated samples will be irradiated. Pieces (25 cm2) will be excised from both the treated and control samples and sent to the food safety lab at MARC for processing. Surviving E. coli O157:H7 will be enumerated by direct plating and MPN procedures. Sensory evaluations will be done on treated and untreated flank steaks and ground beef samples of varying fat content. Product used for sensory evaluation will not be inoculated.</p>