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The consumption of undercooked ground beef contaminated with Escherichia coli O157:H7 has been the leading cause of hemorrhagic colitis and hemolytic uremic syndrome in North America.  One possible way of killing E.coli O157:H7 is through the addition of mustard flour to the ground beef.  Allyl isothiocyanate, a naturally occurring volatile compound in mustard, has been reported as an effective antimicrobial agent against E.coli O157:H7.

The objective of the research was to kill E.coli O157:H7 in ground beef by incorporation of mustard flour at 5,10, or 20% (w/v). 

De-hulled non-deheated mustard flour was mixed with freshly prepared ground beef (20% fat).  A five strain cocktail of E.coli O157:H7 at levels of approximately 10³ or 10⁶ cfu/g was inoculated into the ground beef.  Inoculated ground beef was formed into 100g patties and placed singly in plastic bags (Nylon/EVOH/PE), backflushed with 100% N₂, heat-sealed and stored at 4^oC for 21 days.  Total plate count was determined using trypticase soy agar while E.coli O157:H7 counts were determined on sorbitol MacConkey agar (CT-SMAC). 

Results at 21 days showed that there were 0.5, 3, and 5.4 log decreases from the initial level (10⁶ cfu/g) in meat containing 5, 10 and 20 % mustard flour, respectively.  At the low inoculum level (10³ cfu/g) E.coli was reduced to undetectable levels after 18, 12 and 3 days at 5, 10, and 20% mustard flour, respectively.  The natural microflora of the ground beef was unaffected by the mustard flour ingredient. The sensory evaluation of the cooked ground beef showed that there were no significant differences in palatability preferences (a=0.01) between the control (no mustard) and the 5% level. 

These results show that mustard was able to kill E.coli O157:H7 in ground beef at a concentration that was acceptable to the sensory panelists.