DESTRUCTION OF SALMONELLA SPECIES HEATED IN AQUEOUS SALT-SOLUTIONS BYMICROWAVE-ENERGY

Concentrations of 0.1, 0.5, 0.75, 1.0, and 1.25% wt/vol (0.017, 0.085, 0.13, 0.17, and 0.21 M, respectively) sodium chloride were added to 0 .3 mM phosphate buffer, pH 6.8, and heated by microwave energy to stud y the relationship between salt concentration, temperatures achieved, and microbial destruction. Heating Salmonella spp. in saline solutions for a constant time (45 s) or to a constant final temperature (60-deg rees-C) was also investigated. Fiberoptic thermometry was employed to obtain a temperature profile at specific sites within the solution. Wh en heating for a constant time period, a minimum concentration of 0.75 % wt/vol NaCl was necessary to afford Salmonella spp. significantly (P = 0.05) greater protection than the phosphate buffer control. Sodium, potassium, magnesium, and calcium chloride (1.0% wt/vol) in 0.3 mM ph osphate buffer were also inoculated with a mixture of Salmonella spp. and heated by microwave energy. Of the salts examined, solutions conta ining NaCl consistently achieved the highest final surface temperature and largest temperature gradient from the surface to the bottom of th e container. The amount of destruction of Salmonella spp. heated to a mixed mean final temperature of 60-degrees-C in buffer containing 1.0% wt/vol concentrations of NaCl, KCl, CaCl2, and MgCl2 was 56.4, 71.2, 72.8, and 88.7%, respectively. No relationship was found between the v alency of the cation used and final temperatures achieved.