Journal of Pure and Applied MicrobiologyVol. 2 No. 1

Kinetics of Inactivation of Listeria monocytogen, Clostridium perfringes, Escherichia coli and Salmonella spp. in Ohmic Heated Tomato Juices

U.N. Onwuka*, E.N.T. Akobundu and M.O. Iwe

Department of Food Science and Technology, Micheal Okpara University of Agriculture, Umudike. P.M.B 7267, Umuahia.Abia State, Nigeria.

Received on 11 January 2008 and accepted on 24 February 2008

 

ABSTRACT

Lycopersicum esculentum (tomato) were obtained, washed and processed into juice. The juice was assayed for microbial contamination, and then divided into 4 equal parts of 250ml each. The portions were sterilized and inoculated with prepared samples of Listeria monocytogen, Salmonella spp, Clostridium perfringes and Escherichia coli respectively, then allowed to stand for 24 hours. assayed for growth of the inoculated bacteria. The samples with growth were ohmic heated using copper/aluminum electrodes at 70C and 100C for periods of 0,5,10,15 and 20 minutes respectively. After each treatment, the bacterial survivors were monitored. Data obtained were used to calculate kinetics parameters of pathogen destruction. Result showed a significant difference in bacterial survival (P<0.05) per temperature, heating time and pathogen type. E. coli had the less survivors with a z value of 4C, D value of 4 minutes while Salmonella the highest survivors (log 2.590) at 100C, but at 70C more Clostridium survived. The D values varied from 3-1mins. for E. coli, 8-5 for Listeria monocytogen, 5-3.5 for Salmonella and 9.5-4.5 for Clostridium perfringes at 70-100C. Various z values indicated significant difference(P<0.05), where Salmonella had 20C, Clostridium and Listeria monocytogen -10C, while the least was 4C in E. coli Inactivation energy was least in Salmonella (583.84 ), highest in E. coli (2130.2J/mole). The model was effective in total destructions of the pathogens at 20 minutes irrespective of the type.

Keywords : Ohmic heating, Pathogens, Destruction, Kinetics and Tomato-juice.