Effect of Electrical Stimulation on Meat Microflora: Observations on Agar Media, in Suspensions and on Beef Carcasses

Abstract

Electrical stimulation of beef carcasses did not cause a significant reduction in surface microbial population at three different sampling positions immediately following slaughter. However, significant microbial reduction (P<0.05) was found at position 2 (muscle above aitch bone) but not at position 1 (inside of neck) or position 3 (fat on outside of round) after 72 h of chilling storage. Nine bacterial species from eight different genera commonly associated with meat were inoculated on three different agar media which varied in electrical conductivity. Electrical stimulation of these media caused a reduction in numbers of microorganisms under various voltage and time treatments. Spore-forming bacteria were the most resistant to the electrical treatments. Among the non-spore formers, gram-negative bacteria were more resistant to electrical treatment than gram-positive bacteria. Also, microorganisms inoculated on the lowest resistance medium A revealed greater reduction in numbers than that of the other media with higher resistance. A five log cycle reduction in Escherichia coli, Pseudomonas putrefaciens and Pseudomonas fragi was found in 0.85% saline solution and phosphate buffered saline solution after a 30-V, 5-min treatment, but little change in count was detected in 0 . 1% aqueous peptone or 2.5 M sucrose solution.