Meat Decontamination 53reductions on pork carcasses are achieved
by water of 65 or 80 ° C for 5 seconds
(Eggenberger - Solorzano et al. 2002 ) or
85 ° C for 15 or 20 seconds (Gill et al. 1995,
1997 ). The highest reported reductions
(4.0 to > 4.8 log 10 /cm^2 ) of E. coli O157:H7,
S. Typhimurium, APC, TCC, and
Enterobacteriaceae were achieved by spray-
ing beef carcass surfaces artifi cially contami-
nated with inoculated bovine feces with
water at 95 ° C for 5 seconds (Castillo et al.
1998b, c ). Lower hot - water temperatures,
such as 72 ° C (for 12 to 15 s), 74 ° C (for 12,
18 or 26 s), or 77 ° C (for 8 s), were also effec-
tive in carcass decontamination (Gorman
et al. 1995b, 1997 ; Reagan et al. 1996 ;
Dorsa et al. 1997b, 1998a, b, c ; Graves
Delmore et al. 1997 ). Average reductions of
APC, TCC, E. coli , and inoculated E. coli
O157:H7 and S. Typhimurium achieved at
72 ° C were 3.7, 2.7, 2.7, 1.8, and 2.7 log 10
CFU/cm^2 , respectively (Dorsa et al. 1998b,
c ; Cutter and Rivera - Betancourt 2000 ).
Increasing the water temperature by 2 ° C (i.e.,
74 ° C) enhanced microbial inactivation, com-
pared to 72 ° C, and markedly decreased the
prevalence of pathogens, such as E. coli
O157:H7 (from 27% to 5%), on bovine heads
(Bosilevac et al. 2006 ; Kalchayanand et al.
2008 ), as well as the levels of APC on lamb
adipose tissue (Kochevar et al. 1997b ). In
contrast, lower temperatures, such as those of
warm water (56 ° C), did not contribute to
meat decontamination more than washing
with cold ( < 30 ° C) water (Cutter et al. 1997 ).
One concern with hot water treatments is
their potential undesirable effect on the
appearance of carcass tissue. Hot water treat-
ments at 82 ° C for 10 seconds may cause tem-
porary bleaching of the tissue, as the meat
regains its redness after chilling (Barkate et
al. 1993 ). Other studies indicate that water
temperatures of 85 ° C for 10 – 20 seconds may
confer both substantial microbial reductions
and acceptable appearance of carcasses (Gill
et al. 1995, 1997; 1999 ; Gill and Badoni
1997 ). Long carcass hot water - washing dura-mance that may deliver microbial reductions
additional to those caused by previous water -
washing or knife - trimming (Gorman et al.
1995b ; Reagan et al. 1996 ; Graves Delmore
et al. 1997 ; Castillo et al. 1998b, c ). The
effectiveness of hot - water treatments mainly
depends on the temperature, duration, and
pressure of application (Dorsa et al. 1996b ;
Graves Delmore et al. 1997 ; Kochevar et al.
1997b ; Gill et al. 1996, 1999, 2001 ; Bacon
2005 ). Spraying of hot water is carried out
with properly designed nozzles to meet the
requirements of fl ow rate, droplet size, pres-
sure of water, as well as the spray angle
(Bacon 2005 ). The temperature achieved on
the carcass surface is commonly 6 – 10 ° C
lower than that of sprayed water, depending
on duration of treatment and other factors
(Dorsa et al. 1996b ; Castillo et al. 1998b ;
Eggenberger - Solorzano et al. 2002 ).
Furthermore, the distance of nozzles from the
carcass and the header temperature affect the
turbulence of water fl ow and hence, the heat
transfer from water to the targeted anatomi-
cal location of the carcass by the time of
contact (Bacon 2005 ). As with all water -
washing interventions, the earlier the hot
water is applied the more effective it is in
killing bacteria (Barkate et al. 1993 ).
Studies evaluating the effi cacy of hot
( > 70 ° C) or warm (50 – 60 ° C) water - washing
on chicken, pig, and beef carcasses have
involved immersion, spraying or deluging
with sheets of water. Immersion of whole
broiler carcasses into water (95 ° C) for 3
minutes was capable of reducing APC from
approximately 3 – 4 and 2 – 3 log 10 CFU/cm^2
before treatment on skin and deboned subcu-
taneous meat, respectively, to < 10 CFU/cm^2
(Avens et al. 2002 ). On scalded and/or pol-
ished uneviscerated pork carcasses, the
maximum reported reduction of natural
microbial contamination (e.g., mesophilic
aerobic bacteria and E. coli ) by commercial
application of hot water ranged from 2
to 3 log 10 /cm^2 (Gill et al. 1995, 1997 ;
Eggenberger - Solorzano et al. 2002 ). Such