Submitted to: Journal of Food Safety
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/3/2003
Publication Date: 1/3/2003
Citation: NIEMIRA, B.A., SOMMERS, C.H., FAN, X., SOKORAI, K.J. FORMULATION OF SOY- AND BEEF-BASED READY TO EAT FOOD PRODUCTS INFLUENCES RADIATION SENSITIVITY OF SURFACE-INOCULATED LISTERIA MONOCYTOGENES AND POST-IRRADIATION PRODUCT SENSORY PROPERTIES. JOURNAL OF FOOD SAFETY. 2003. V. 23. P. 35-46. Interpretive Summary: Ionizing radiation can eliminate pathogenic bacteria from ready-to-eat food products such as frankfurters, but the composition of the product can influence the efficacy of the process. An outbreak strain of an important foodborne pathogen (Listeria monocytogenes) was inoculated onto a) three different meatless, soy-based commercial frankfurter products, b) soy-based commercial tofu and c) a beef frankfurter commercial product. The amount of radiation required to reduce the bacterial population by 90 percent was significantly greater on all of the soy frankfurters than on the beef frankfurter or the tofu. The antioxidant strength of the products also varied significantly, but was not correlated with the radiation sensitivity of the bacteria. To determine the impact of irradiation on the color and texture of the products, the products were treated with radiation doses sufficient to eliminate approximately 99 percent or 99.999 percent of the bacteria. Ionizing radiation significantly decreased redness in the beef frankfurter and one of the soy frankfurters, but significantly increased redness in another soy frankfurter. The texture of the beef frankfurter and one of the soy frankfurters was significantly decreased following irradiation. The product formulation was found to be key in determining the product response to irradiation. The food processing industry will benefit from a more efficient method of eliminating Listeria monocytogenes and the consumer will benefit from a safer food product.
Technical Abstract: Ionizing radiation can eliminate pathogenic bacteria from ready-to-eat (RTE) food products. To determine the effect of antioxidant power on the radiation sensitivity of Listeria monocytogenes, an outbreak strain of L. monocytogenes was irradiated after inoculation onto a) three meatless, soy-based frankfurter products ("Soy1 , "Soy2 , "Soy3), b) soy-based tofu ("Tofu") and c) a beef frankfurter product ("Beef"). The D10 (the amount of radiation required to reduce the bacterial population by 90%) was significantly influenced by the substrate: Beef (0.622kGy) = Tofu (0.622kGy) < Soy2 (0.680kGy) = Soy3 (0.695kGy) <Soy1(0.761kGy). The antioxidant strength of the products also varied significantly, but was not correlated with the D10 values obtained. To determine the sensory impact of irradiation, the products were treated with 1.5 kGy or 3.2 kGy, doses equivalent to 1.9-2.4 or 4.2-5.1 log10 reductions, respectively. These doses significantly decreased redness in Beef and Soy2, and significantly increased redness in Soy3. The maximum shear force of Beef and Soy1 was significantly decreased following irradiation. Product formulation was found to be key in determining the product response to irradiation.