ELECTRON BEAM IRRADIATION ON NALIDIXIC ACID‐RESISTANT SALMONELLA MONTEVIDEO IN COOKED TOMATO PUREE OF VARIOUS pH VALUES

Abstract

ABSTRACT Electron beam (e‐beam) is a technology that uses ionizing radiation to destroy bacteria in a nonthermal manner. D10 values were obtained for nalidixic acid (NA)‐resistant Salmonella Montevideo in autoclaved Roma tomato puree pH adjusted to pH 3.4, 3.9, 4.4 and 4.9 and subjected to e‐beam at 0 (control), 0.5, 1.0, 1.5, 2.0 and 2.5 kGy. Survivors were enumerated using standard spread‐plating method. NA‐resistant S. Montevideo was not recovered in puree at pH 3.4 or 3.9. Significant reductions (P < 0.05) were determined at both pH 4.4 and 4.9 between the control (0 kGy) and samples exposed to≥1.5 kGy. D10 values were 1.07 and 1.50 kGy, respectively, which are greater than previously published D10 values for other Salmonella strains in various media. Tomato puree has antioxidant potential which may have provided protection against the e‐beam radiation. Radiation resistance as a result of acid adaptation may have also contributed to this effect.PRACTICAL APPLICATIONSElectron beam (e‐beam) irradiation is a nonthermal technology that uses ionizing radiation to destroy bacteria and spoilage microorganisms. Several studies have shown this technique effective for the reduction of bacterial pathogens on fruits and vegetables with no changes in texture, color or sensory quality. Some studies have suggested that the food matrix may influence sensitivity of bacterial strains to irradiation; therefore, the objective of this experiment was to determine the e‐beam radiation dose needed to achieve a one log reduction in population (D10 value) for nalidixic acid‐resistant Salmonella Montevideo in a tomato puree at low and high pHs.