52 Chapter 3
properly, with well - functioning equipment.
Simple water - washing alone may not be suf-
fi cient for major improvements in carcass
hygiene, unless it is followed by other physi-
cal or chemical decontamination methods,
which are discussed in the next sections.Thermal Decontamination
Research on meat decontamination since the
1980s has shown that the effectiveness of
physical decontamination methods may be
signifi cantly enhanced when the carcass
surface temperature is raised above 70 ° C
(Kelly et al. 1981 ; Davey and Smith 1989 ;
Smith 1992 ). Currently, commercially ap -
plied thermal treatments worldwide include
hot water (70 – 85 ° C) or saturated steam to
reduce microbial contamination on carcasses.
Both interventions are commercially applied
post - evisceration, after fi nal carcass - washing
(Fig. 3.1 ), whereas hot water has also been
evaluated as potential decontamination treat-
ment of carcass trimmings. While hot water
treatments may be applied in spraying cabi-
nets equipped with proper nozzles, steam
pasteurization requires the installation of
more expensive steam cabinets. The com-
mercial application of steam pasteurization
costs more than hot water. According to
a recent review by Midgley and Small
(2006) , hot water requires approximately
$400,000 – $500,000 for the installation of
proper equipment and results in an average
cost of $0.60 – $0.70 per carcass, whereas
the respective costs estimated for steam pas-
teurization are $650,000 and up to over $1
million and $0.75 – $0.80 per carcass, depend-
ing on the number of carcasses processed per
hour.Hot - Water Decontamination
Hot water (74 – 97 ° C) exerts decontamination
effects through physical removal and thermal
inactivation of bacteria present on the surface
of meat. It is an intervention of high perfor-of beef carcasses spread the microbial con-
tamination in a posterior to anterior direction,
following the fl ow of wash water, down the
carcass (i.e., from hind leg to forequarter).
Similarly, power - hosing of pork carcasses
after singeing increased bacterial numbers on
ham, belly, and neck by almost 3 log 10 CFU/
cm^2 (Bolton et al. 2002 ). Polishing of pig
carcasses following singeing and/or scalding
may increase APC, further necessitating a
pre - chilling washing/decontamination step
(Gill et al. 1995, 2000 ; Yu et al. 1999 ).
However, due to the aforementioned limita-
tions, pre - chilling washing may be insuffi -
cient to reduce the microbial contamination
of carcasses entering the dressing process,
especially if the dressing process is not
implemented under controlled hygienic con-
ditions (Gill et al. 2000 ). In a comparative
evaluation of the hygienic performance of
eight pork plants, it was found that APC,
TCC, and E. coli after fi nal washing were
equal to or higher than after polishing in
the majority of plants, suggesting that
microbial contamination was either depos-
ited on carcasses or not removed from car-
casses during the dressing process (Gill et al.
2000 ).
In conclusion, spray - washing with tap/
potable water may have a moderate effect
on microbial reduction but it is very effective
in improving the visual appearance of car-
casses. Nonetheless, if not done properly,
spray - washing may lead to: (i) increased
surface tissue moisture; (ii) entrapment,
embedding, and subsequently potential pro-
liferation of bacteria into tissues; entrapment
and embedding may also act as a physical
barrier against subsequent decontamination
interventions; (iii) reduction of endogenous
spoilage microfl ora and thus of their com-
petitive effect on pathogens; and, (iv) redis-
tribution or translocation of microbial
contamination from heavily contaminated to
cleaner parts of carcasses (Cabedo et al.
1996 ; Bacon 2005 ). Therefore, it is suggested
that water spray - washing should be done