Meat Decontamination 47TCC (Castillo et al. 1998a ; Graves Delmore
et al. 1998 ).
In commercial applications, chemical
dehairing reduced visible contamination
(i.e., hair and carcass defects) and the amounts
of waste derived from carcass trimming
compared to the conventional process, but it
had negligible effect in reducing carcass
bacterial loads (Schnell et al. 1995 ). This
was attributed to the fact that dehairing was
evaluated during breaks on days when non -
dehaired animals were also processed in
the same facility, and thus, the plant environ-
ment carried microbial contamination (e.g.,
via aerosol, human, and equipment) from
conventionally slaughtered animals. Nou
et al. (2003) evaluated the APC,
Enterobacteriaceae counts, and prevalence
of E. coli O157:H7 on 240 conventionally
processed beef carcasses, 240 hides that were
chemically dehaired before removal, and
on two respective sets of 240 carcasses
immediately after hide removal at pre -
evisceration in a plant that processed only
dehaired animals. It was shown that the APC
and Enterobacteriaceae populations on car-
casses at pre - evisceration that had received
chemical dehairing were lower than those on
conventionally processed carcasses by 2 and
1.8 log 10 CFU/cm^2 , respectively. Similarly,
the prevalence of E. coli O157:H7 on dehaired
and nondehaired carcasses was reduced from
67% (pre - treatment) to 1% and from 88% to
50%, respectively (Nou et al. 2003 ). When
simulated chemical dehairing systems were
tested in vitro on removed whole beef hides
inoculated with E. coli O157:H7 and
Salmonella , Carlson et al. (2008b) found that
deluging with SS (6.2%, 30 ° C) or potassium
cyanate (PC; 2.4%, 30 ° C) reduced E. coli
O157:H7 by 4.8 – 5.1 log 10 CFU/cm^2 and
Salmonella by 0.7 (PC) and 4.2 (SS) log 10
CFU/cm^2.
Physical separation of the dehairing
process from the hide removal operations
would limit microbial aerosols and the spread
of hydrolyzed hair and residual dehairingsimulated low - pressure (2.07 bar, 7 s) chemi-
cal sprays on whole beef hides inoculated
with E. coli O157:H7 and Salmonella ,
Carlson et al. (2008a, b) found that 10% of
warm (55 ° C) lactic or acetic acid, or cold
(23 ° C) solutions of sodium metasilicate (SM;
4%), SH (3%), and SH (1.5%) in combina-
tion with chlorinated water (200 ppm)
reduced the inoculated levels of the above
pathogens by > 2 log 10 CFU/cm^2. The above
chemical treatments also caused similar
reductions to the populations of total bacte-
ria, coliforms, and E. coli (Carlson et al.
2008a ).
In conclusion, strict hygienic measures
need to be applied during animal transporta-
tion to the abattoir and further handling
before the dressing process. Animal washing
may reduce microbial contamination on the
external animal surfaces. However, this inter-
vention has variable results and its effective-
ness is uncertain. Nevertheless, application
of low - pressure spray rinses with approved
chemicals, such as detergents, organic acids,
hydrogen peroxide, and chlorine, on animal
hides is practiced in the United States and
Australia (Midgley and Small 2006 ; Stopforth
and Sofos 2006 ).
Dehairing
Chemical dehairing of cattle hides is a pat-
ented process (Bowling and Clayton 1992 )
that received FSIS - approval for experimental
testing by the industry (Sofos and Smith
1998 ). The aim of chemical dehairing is to
remove hair, mud, manure, other extraneous
matter, and associated microbial contami-
nants from animal hides before their removal
from carcasses. Applications ( in vitro ) of
chemical dehairing on artifi cially inoculated
bovine hide samples suggested that treatment
with 10% sodium sulfi de (SS) for 16 seconds
could achieve > 3 log cfu/cm^2 reductions of
inoculated E. coli O157:H7, Salmonella spp.,
L. monocytogenes , as well as of APC and