50 Chapter 3
removal but before evisceration (Fig. 3.1 ).
Organic acids, such as lactic and acetic, are
the chemicals of choice in pre - evisceration
treatments. However, due to the strong fl avor
of acetic acid, lactic acid is the preferred
compound. Details on the effect of chemical
solutions on the reduction of carcass micro-
bial contamination are presented in the
“ chemical decontamination ” section of this
chapter.
Given that bacterial attachment increases
with time elapsed between exposure of the
carcass to contamination and application of
the decontamination treatment, the sooner
the application of spray - washing after hide
removal the higher the expected result. It is
believed that pre - evisceration washing is
effective, as it may limit the adherence of
bacteria to carcass by reducing the surface
tension (i.e., the surface free energy and
contact angle) of the latter (Dickson 1995 ).
Consequently, spray - washing before evis-
ceration may result in signifi cant reduction of
initial contamination because of the short
time for bacterial and soil attachment after
hide removal, and because the wet surface
limits subsequent bacterial attachment during
evisceration and before fi nal carcass - washing
(Sofos and Smith 1998 ).Final Carcass - Washing
As indicated, water - washing is also applied
at the end of the dressing process (post -
evisceration), following zero - tolerance
inspection, before carcass - chilling. Typically,
carcass - washing may take place manually
with hand - held hoses in small operations or
by automated spraying systems in cabinets
(Anderson et al. 1981 ), in which the nozzle
type and confi guration, and the spraying
pressure determine the droplet size and tem-
perature of water as it hits the carcass surface
(Bacon 2005 ). The main objective of fi nal
carcass - washing is to improve the appear-
ance of the carcass by removing blood and
sawdust generated during carcass - splitting.However, steam - vacuuming seems to be a
useful decontamination approach on hot car-
casses during dressing, as it may deliver sig-
nifi cant reductions of APC and TCC.
Implementation of water/steam - vacuuming
reduces the amount of trimming needed on
carcass - processing lines and hence, limits the
effect of human subjectivity, as well as the
risks of contamination by insuffi cient sanita-
tion of knives and improper personnel
hygiene. In addition to visible contaminated
spots, steam - vacuuming operators in U.S.
slaughter plants also apply the intervention
on certain carcass sites (e.g., hide cutting
pattern lines) known to carry microbial con-
tamination even in the absence of visible soil.
It should be noted that the effectiveness of
this intervention depends on appropriate
application and proper state of equipment
operation.
Pre - Evisceration Decontamination
Pre - evisceration interventions include
washing with cold or hot water and/or rinsing
with chemical solutions, such as organic
acids (Fig. 3.1 ). In addition, water - washing
of beef carcasses is performed as a fi nal step
before decontamination and chilling (Fig.
3.1 ). Washing with cold water may be con-
sidered equally or less effective than knife -
trimming in removing bacterial contamination,
whereas the combination of both treatments
may not be more effective than each treat-
ment alone (Gorman et al. 1995a, b ; Gill et
al. 1996 ; Graves Delmore et al. 1997 ; Reagan
et al. 1996 ). However, this comparison may
be unjustifi ed, since knife - trimming applies
to defi ned carcass segments, while washing
applies to whole carcasses. Compared with
cold water, which physically removes bacte-
ria, hot water - washing has an additional
lethal effect on microbial contamination (see
relevant section of this book chapter).
Apart from water - washing, rinsing with
chemical solutions may also be effective in
reducing microbial contamination after hide