Meat Decontamination 49quent vacuum removes the contaminants.
Kochevar et al. (1997a) tested two commer-
cial steam - vacuuming systems according to
the operation protocol applied in operating
plants. They found that steam - vacuuming
caused 1.7 – 2.0 and 1.7 – 2.1 log 10 /cm^2 reduc-
tions of APC and TCC, respectively, which
were slightly higher than reductions achieved
by knife - trimming. Decrease in microbial
populations due to steam - vacuuming may
also exceed those achieved with water spray -
washing (Castillo et al. 1999a ). In general,
reported reductions of APC, TCC, and E. coli
by steam - vacuuming of naturally contami-
nated carcasses have ranged from 0.5 to
2 log 10 CFU/cm^2 (Gill and Bryant 1997b ;
Kochevar et al. 1997a ), whereas those on
tissues artifi cially inoculated with bovine
feces are commonly higher, such as 3 – 4 log 10
CFU/cm^2 (Dorsa et al. 1996a ; Castillo et al.
1999a ). Considerable effectiveness of steam -
vacuuming has also been shown against
pathogens artifi cially inoculated on beef
carcass short plates or cutaneous trunci
muscles. Specifi cally, average reported
reductions of L. innocua , L. monocytogenes ,
S. Typhimurium, and vegetative cells of
Clostridium sporogenes ranged from 2 to
3.4 log 10 CFU/cm^2 (Dorsa et al. 1997b ;
Phebus et al. 1997 ), whereas a reduction
of 5.5 log 10 CFU/cm^2 has been reported for
inoculated E. coli O157:H7 (Dorsa et al.
1996b ).
The duration of vacuum application, the
processing stage, and the type or state of beef
tissue seem to play an important role on the
effi ciency of steam - vacuuming. Bacon et al.
(2002a) evaluated post - chilling steam - vacu-
uming (130 ° C, 1.72 bar) on Salmonella -
inoculated cold beef adipose tissue surfaces
and found reduction of less than 1 log 10 CFU/
cm^2. The limited effi cacy of the applied treat-
ment was attributed to the short contact time
of the steam - vacuuming unit with the adipose
surface, in combination with the protective
effect of the hardened cold surface on micro-
colonies imbedded or attached to the tissue.ing the trimming and the proper sanitation of
the knives used. To ensure better decontami-
nation of knives after use on a carcass, the
industry in the United States has introduced
the two - or three - knife system. As one knife
is used, the others remain immersed in hot
water for decontamination. Furthermore,
given that knife - trimming removes visible
contamination, it is likely that low - level con-
tamination, as well as contamination which
is not associated with visible soil, may be
ignored (Edwards and Fung 2006 ). Thus,
alternative decontamination methods, such as
steam - vacuuming, but especially whole - car-
cass treatments in the form of multiple inter-
ventions, such as consecutive application of
trimming and spraying with hot (66 to
87.8 ° C) water or chemical solutions, are nec-
essary to improve the microbiological quality
of carcasses (Dorsa 1997 ).
Steam/Hot Water - Vacuuming
In response to the need for interventions
alternative to knife - trimming for removal of
visible contamination from carcasses, FSIS
approved the cleaning of carcass spots of up
to 2.5 cm in diameter with handheld equip-
ment, applying steam and vacuum; larger
spots must be removed only by knife - trim-
ming (USDA - FSIS 1996a ). The aim of the
steam - vacuuming process is to clean visible
soil as well as to remove or kill associated
microorganisms (Kochevar et al. 1997a ). A
very large portion of the U.S. meat industry
applies this economical process throughout
the slaughter chain (Gill and Bryant 1997b ).
Commercial steam - vacuuming units release
steam (at 104 – 110 ° C, 2.07 – 3.45 bar) and/or
hot water (at 82 – 94 ° C, 0.34 – 1.03 bar) in con-
junction with the application of vacuum and
are continuously heat - sanitized (Dorsa et al.
1996a, b, 1997b ; Kochevar et al. 1997a ;
Castillo et al. 1999a ). The principle of the
method is described as follows: initial appli-
cation of steam or hot water loosens soil and
causes bacterial inactivation, while subse-