Escherichia (E.) coli O157:H7 survival in dry cured (uncooked) meat products leading to human illness outbreaks is an international problem. Their manufacture does not involve a heat kill step to ensure the destruction of the organism, and the adverse conditions created during processing may not be sufficient to prevent E. coli O157:H7 survival. Deodorized yellow mustard powder has antimicrobial properties from glucosinolate (sinalbin) hydrolysis catalyzed by the endogenous enzyme myrosinase, generating antimicrobial isothiocyanate (PHBIT). Previous work has shown that its addition during dry sausage manufacture was capable of eliminating the pathogen. In this study, its use for the same purpose was investigated during dry cured Westphalian ham production. Hams were inoculated with a 7.5 log cfu•g-1 cocktail of E. coli O157:H7, surface applied with 4% or 6% (w/w) deodorized yellow mustard powder, and monitored for E. coli O157:H7 survival during 80d ham maturation. One trial included the inoculation of Staphylococcus (S.) carnosus, a meat starter culture with myrosinase-like activity, onto the hams (after salt equilibration) to accelerate formation of antimicrobial isothiocyanate from mustard glucosinolate and help control the pathogen. In both trials, E. coli O157:H7 was reduced 3 log cfu•g-1 by 21d on hams treated with mustard powder, whereas only a 1 log cfu•g-1 reduction was found in the inoculated control which was not treated with mustard. By 45d, hams treated with mustard powder showed a reduction of >5 log cfu•g-1 E. coli O157:H7, whereas it took 80d to for numbers in control hams to be similarly reduced. Since a 5 log kill of E. coli O157:H7 was achieved in control hams by the end of 80d, dry cured Westphalian ham manufacture would be considered capable of controlling the risk of E. coli O157:H7 survival by North American regulatory agencies. However, deodorized yellow mustard powder at 4%, and to a greater extent at 6%, eliminated the pathogen at a significantly faster rate than the control during ham processing. Addition of the S. carnosus starter culture in trial 2 may have contributed to the maintenance of this effect through isothiocyanate formation. It also helped restore numbers of staphylococci, which were found to be sensitive to deodorized mustard powder.

Yellow and oriental mustards deodorized by a laboratory autoclave method have been shown to reduce the number of E. coli O157:H7 greater than the mandatory 5 log CFU/g during sausage manufacture. However, E. coli O157:H7 was inconsistently controlled by different deodorized mustards. The antimicrobial action of mustard results from the conversion of naturally present glucosinolates into inhibitory isothiocyanates by plant myrosinase in untreated hot mustard and by bacterial myrosinase-like activity when present in thermally-treated (deodorized) mustard. Variable results with deodorized mustards suggested that plant myrosinase might not have been completely inactivated during laboratory thermal treatment using the autoclave. Results obtained showed that when a 2 cm thick layer of mustard was used during autoclave treatment, plant myrosinase activity periodically remained. However, the completely deodorized mustard failed to reduce bacterial viability as effectively as yellow mustard containing residual or slight amount of myrosinase. As a result, a small amount of myrosinase activity was highly likely contribute to the overall antimicrobial activity of deodorized mustard against E. coli O157:H7 in dry sausage.

Escherichia (E.) coli O157:H7 survival in dry cured (uncooked) meat products leading to human illness outbreaks is an international problem. Their manufacture does not involve a heat kill step to ensure the destruction of the organism, and the adverse conditions created during processing may not be sufficient to prevent E. coli O157:H7 survival. Deodorized yellow mustard powder has antimicrobial properties from glucosinolate (sinalbin) hydrolysis catalyzed by the endogenous enzyme myrosinase, generating antimicrobial isothiocyanate (PHBIT). Previous work has shown that its addition during dry sausage manufacture was capable of eliminating the pathogen. In this study, its use for the same purpose was investigated during dry cured Westphalian ham production. Hams were inoculated with a 7.5 log cfu•g-1 cocktail of E. coli O157:H7, surface applied with 4% or 6% (w/w) deodorized yellow mustard powder, and monitored for E. coli O157:H7 survival during 80d ham maturation. One trial included the inoculation of Staphylococcus (S.) carnosus, a meat starter culture with myrosinase-like activity, onto the hams (after salt equilibration) to accelerate formation of antimicrobial isothiocyanate from mustard glucosinolate and help control the pathogen. In both trials, E. coli O157:H7 was reduced 3 log cfu•g-1 by 21d on hams treated with mustard powder, whereas only a 1 log cfu•g-1 reduction was found in the inoculated control which was not treated with mustard. By 45d, hams treated with mustard powder showed a reduction of >5 log cfu•g-1 E. coli O157:H7, whereas it took 80d to for numbers in control hams to be similarly reduced. Since a 5 log kill of E. coli O157:H7 was achieved in control hams by the end of 80d, dry cured Westphalian ham manufacture would be considered capable of controlling the risk of E. coli O157:H7 survival by North American regulatory agencies. However, deodorized yellow mustard powder at 4%, and to a greater extent at 6%, eliminated the pathogen at a significantly faster rate than the control during ham processing. Addition of the S. carnosus starter culture in trial 2 may have contributed to the maintenance of this effect through isothiocyanate formation. It also helped restore numbers of staphylococci, which were found to be sensitive to deodorized mustard powder.