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Abstract
Shiga-toxin producing Escherichia coli (STEC) are one of the important pathogens of concern in various foods and beef in particular. This research was aimed at evaluating the efficacy of various non-chemical treatments such as, continuous ultra violet radiation (UV-C), infra-red radiation (IR), and pulsed UV (PUV) on different strains of E. coli O157:H7, several non-O157 serotypes and surrogates in pure culture as well as on cattle hides and beef trims. Nalidixic acid adapted strains (Nal) were subjected to UV-C, IR, and PUV in order to test their resistance against the resistance of parent strains (Par). The results showed that there were some significant (P<0.05) differences between the resistance of Nal and Par strains when subjected to the above said three non-chemical treatments. The results show that E. coli O157:H7, strain 5 was the most resistant strain with a D value of 86.8 sec. Strain 5Par of E. coli O157:H7 was also the most resistant among all the parent strains and serogroups when subjected to PUV treatment with a D value of 1.01 J/ cm2.In the second phase of the study efficacy of UV-C, IR, and PUV on reducing the STEC on cattle hides was studied. Results indicate that IR produced the highest reduction of 3.72 log CFU/ cm2 of E. coli O157:H7 population on hide. Wash treatments followed by IR resulted in more reduction than wash followed by PUV. The research also aimed at evaluating the antimicrobial efficacy of PUV treatments as well as different organic acid spray treatments including lactic acid (LAC), Blitz (BTZ), Beefxide (BTZ), and de-ionized water (WTR), and combination of PUV followed by organic acid spray treatments (LAC+P, BTZ+P, BFX+P, and WTR+P} on beef muscle samples spiked with E.coli O157:H7 and Salmonella Typhimurium DT 104. It was observed that PUV for short duration of time can be an effective treatment option for decontamination of beef trims. The combination treatments if appropriately applied can yield significant (P<0.05) pathogen reductions in beef trims as well as on ground beef.