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

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 APPLICATIONS Electron 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.

Application of electron beam to inactivate Salmonella in food: Recent developments

“…James, Jaczynski, and Matak (2010) determined the antimicrobial efficacy of e-beam against acid-resistant S. Montevideo in tomatoes with varying acidity. Tomatoes were subjected to e-beam at 0 (control), 0.5, 1.0, 1.5, 2.0 and 2.5 kGy.…”

Radioresistance development of DNA repair deficientEscherichia coliDH5α in ground beef subjected to electron beam at sub-lethal doses

“…Ionising radiation effectively inactivates microorganisms including foodborne pathogens (Farkas 1998, Black and Jaczynski 2006, 2007, Chalise et al 2007, O'Bryan et al 2008, Arvanitoyannis et al 2009, Arvanitoyannis and Stratakos 2010, James et al 2010. Therefore, application of ionising radiation to food processing enables food manufacturers to increase microbial food safety and extend shelf-life of food products.…”

Impact of irradiation on the microbial ecology of foods

“…It has been shown that Salmonella contaminates the surface of vegetables and enters into the edible parts of different varieties of plants like lettuce, tomatoes, radish sprouts, bean sprouts, and barley (Tahergorabi et al, 2012). James et al (2010) studied the effect of e-beam on S. Montevideo inactivation in tomatoes. They observed significant reductions in the number of microorganisms subjected to >1.5 kGy irradiation.…”