The Effect of Liquid Smoke on Listeria monocytogenes ¹

Although no documented outbreaks of listeriosis have been associated with the consumption of meat in the United States, Listeria monocytogenes is common to the environment of processing plants. In an effort to control the potential hazard of surface contamination of beef franks with L. monocytogenes , five different Red Arrow smoke products were evaluated for their antimicrobial activity in 0.5% and 0.25% smoke preparations against L. monocytogenes LCDC 81-861, a serotype 4b strain. In smoke preparations of 0.5%, CharSol-10, Aro-Smoke P-50, and CharDex Hickory were effective in reducing viable cell numbers below detection within 4 h and CharSol PN-9 and CharOil Hickory gave similar results within 24 h. In smoke preparations of 0.25%, CharSol-10 and Aro-Smoke P-50 again demonstrated their strong antimicrobial effects within 4 h, but the activity of CharDex Hickory, CharSol PN-9, and CharOil Hickory are reduced at this concentration requiring 24, 48, and 96 h, respectively, to reduce microbial numbers below detection. Since CharSol-10 demonstrated strong antimicrobial effects against L. monocytogenes in pure culture, it was selected as the liquid smoke to be used as a full strength dip treatment for beef franks surface inoculated with 6 strains of L. monocytogenes then vacuum packaged and stored at 4±l°C for 72 h. In untreated beef franks, L. monocytogenes numbers remained unchanged after 72 h, while beef franks dipped in CharSol-10 liquid smoke exhibited a greater than 99.9% reduction in L. monocytogenes numbers after 72 h of storage.