Meat Decontamination 67(Koutsoumanis et al. 2004 ). Likewise,
Castillo et al. (1998c, 1999a) found fewer
beef carcasses with Enterobacteriaceae
above 1 log 10 CFU/cm^2 , or positive for
Salmonella and E. coli O157:H7, when hot
water was applied before lactic acid.
However, delaying the application of lactic
acid after water - washing further enhances the
effectiveness of acid treatment by minimiz-
ing the dilution of acid concentration by the
residual surface moisture (Gill and Landers
2003b ).
Stopforth et al. (2005) performed a study
simulating application of multiple decontam-
ination treatments (each one for 30 s), includ-
ing lactic acid, ammonium hydroxide, SM,
and acidifi ed or basic electrolyzed oxidized
water, in order to reduce initial E. coli
O157:H7 and S. Typhimurium contamination
levels of 5.6 – 5.7 log 10 CFU/cm^2 on beef
tissue. Sequential applications involving use
of SM or lactic acid application were the
most effective, achieving 1.1 – 2.0 log 10 CFU/
cm^2 reductions (Stopforth et al. 2005 ).
Furthermore, in a multiple - hurdle decontami-
nation system of carcasses pre - and post -
evisceration, as well as pre - and post - chilling,
the combinations of either two lactic acid
applications, or at least one hot and one lactic
acid application, were more effective than
multiple hot - water or single lactic acid sprays
(Stopforth et al. 2005 ). More detailed exam-
ples of the performance of multiple decon-
tamination interventions are provided in
Table 3.1.
The above suggests that all the physical
and chemical decontamination treatments
described may be used as multiple interven-
tions from the stage of animals arriving at the
abattoir, during the dressing process, until
chilling and fabrication, in order to reduce
microbial contamination on hides, carcasses,
and cuts. Currently, the U.S. beef industry
uses sequential and simultaneous inter-
ventions, such as animal washing, knife -
trimming, steam - vacuuming, pre - evisceration
washing/rinsing, washing with hot waterby testing the effi cacy of multiple spray -
washing/rinsing treatments in the laboratory
utilizing warm/hot water and/or acetic acid
solution separately and in sequence to reduce
microbial contamination on beef tissue inoc-
ulated with E. coli. Treatments applied
achieved variable reductions of APC, E. coli ,
and TCC in the range of < 1 to 1.7 or 4.3 log 10
CFU/cm^2 (Graves Delmore et al. 1998 ).
Furthermore, the combination of steam - vac-
uuming with hot (72 or 95 ° C at 24 bar for
5 s) and then cold (30 ° C) water, and/or 2%
lactic acid (55 ° C, 11 s) increased log - reduc-
tions of aerobic bacteria, indicator organ-
isms, and pathogens up to 4.3 – 5.3 log 10 CFU/
cm^2 , as compared with 1 – 3 log 10 CFU/cm^2
reductions obtained by application of single
treatments (Dorsa et al. 1996b ; Castillo et al.
1999a ; Phebus et al. 1997 ). Likewise, appli-
cation of chemical agents, such as 1.8%
acetic acid, increased the decontamination
effi cacy of hot water (80 ° C) by 2 log 10 CFU/
cm^2 and also reduced the number of positive
E. coli samples (Eggenberger - Solorzano et
al. 2002 ). The impact of consecutive water -
washings (i.e., fi rst with hot and then with
cold water) is weaker compared with the
combination of hot water with chemical
agents (Dorsa et al. 1996b ; Stopforth et al.
2005 ). Moreover, the order of application of
hot water and lactic acid is important for the
microbial reduction and residual antimicro-
bial effects during storage (Castillo et al.
1998c, 1999a ; Koutsoumanis et al. 2004 ).
Koutsoumanis et al. (2004) found that appli-
cation of hot water (75 ° C) fi rst, followed by
lactic acid (2%, 55 ° C; HW - LA), was more
effective than the reverse sequence (LA - HW)
in delaying growth of L. monocytogenes
during storage (4, 10, and 25 ° C) of vacuum -
packaged beef tissues. Possible reasons for
HW - LA being more effective than LA - HW
include cellular damage by heat and suscep-
tibility of injured cells to subsequent acid
exposure, while application of hot water
after acid treatment may reduce residual
acid levels on the surface of treated meat