Determination of the Effect of Milk Fat on the Inactivation of Listeria monocytogenes by Ohmic Heating

: Research in recent years has focused on innovative technologies provide pathogen inactivation without damaging the structural properties of foods. Ohmic heating (OH) is an innovative technology, providing an effective microbial inactivation with massive and rapid heating. This study aims to determine the effects of milk fat on the inactivation of Listeria monocytogenes by OH with a low voltage gradient. L. monocytogenes inoculated 3. 1%, 1. 5%, and 0. 1% fat-milk samples were heated up to 62 °C by OH and conventional heating (CH) process. OH treatment lead to inactivation of L. monocytogenes in both 1. 5% and 0. 1% groups and led to approx. 5. 30 log decrease, however, there was only a 3. 10 log decrease in 3. 1% group at 6 min. CH lead to a few reduction as 0. 21, 0. 29 and 0. 39 log in 3. 1%, 1. 5% and 0. 1% fat-milk respectively. The sublethal injury ratio in OH was higher than CH in all milk groups. While OH, did not statistically change color and pH values at the 6th min of the process, had a significant effect on Hydroxymethylfurfural value only in 3. 1 % fat-milk. In conclusion, the increased fat content may have important inhibitory effects on pathogen inactivation in OH. Thus, the OH conditions should be chosen carefully to sufficient inactivation of pathogens in milk with high-fat content.