MICROBIOLOGICAL AND CHEMICAL INVESTIGATION OF OHMIC HEATING OF PARTICULATE FOODS USING A 5-KW OHMIC SYSTEM

Lethality within food particles undergoing ohmic heating was investiga ted using microbiological and chemical marker measurements. Meatballs containing spores of B. stearothermophilus and precursors of chemical markers were thermally processed in a starch solution with 30-40% soli ds content using a 5 kilowatt (kW) ohmic system. Different temperature s, flow rates, holding tube lengths, and fluid electrical conductiviti es were used. Lethalities observed under various processing conditions were consistent with predictions. Higher lethality was observed, micr obiologically and chemically, at the center of the meatballs rather th an near the surface. A good correlation between the marker yield and t he bacterial survivor population was obtained under various processing conditions. The results indicate that the chemical markers may be use d to evaluate the distribution of lethality among different particles and the contribution to lethality of different holding sections. The r esults also suggest that sterility of ohmically heated particulate foo ds may be evaluated, to a first approximation, based on the fluid temp erature and the residence time (i.e., holding tube geometry/flow rate) .