62 Chapter 3
perature (30 – 70 ° C) did not infl uence the
effectiveness of 2% acetic acid for 15 seconds
(Cutter et al. 1997 ), while an increase in tem-
perature from 55 to 65 ° C had a signifi cant
infl uence on the effectiveness of 2% or 4%
lactic acid for 15 or 30 seconds (Castillo et
al. 2001b ). With respect to the concentration
alone, the effectiveness of lactic, acetic, and
citric acid spraying rinses (24 or 32 ° C)
against total bacterial counts, L. innocua , E.
coli O157:H7, and C. sporogenes on beef
carcass tissue was found to increase with
concentration from 1.5% to 5% (Castillo et
al. 2001b ; Cutter and Siragusa 1994b ; Dorsa
et al. 1997a ). Furthermore, an increase in the
concentration, temperature, and duration of
post - chilling lactic acid treatment from 2% to
4%, 55 to 65 ° C, and 15 to 30 seconds, respec-
tively, enhanced reduction of E. coli (Castillo
et al. 2001b ). Nonetheless, concentrations
exceeding 2% may cause discoloration or
compromise fl avor, and thus, levels of 1.2%
to 2% at 55 ° C were recommended (Woolthuis
and Smulders 1985 ; Bell et al. 1986 ; Dickson
and Anderson 1991 ; Goddard et al. 1996 );
however, levels of up to 5% are also used
even post - chilling.
Organic acid treatments are more effec-
tive against low - compared with high -
contamination levels (Greer and Dilts 1992 ;
Cutter et al. 1997 ). The target organisms and
meat tissue also affect microbial reductions
caused by organic acids. For instance, P.
fl uorescens was less resistant to lactic, acetic,
and citric spray rinses than E. coli (Cutter and
Siragusa 1994b ) and so was S. Typhimurium
compared with E. coli O157:H7 when
exposed to spray rinses with lactic or acetic
acid (Hardin et al. 1995 ). Higher microbial
reductions were obtained on adipose than on
lean tissues (Cutter and Siragusa 1994b ;
Dickson 1988 ). However, the inside round
of carcass, in which fecal material and asso-
ciated microorganisms may be imbedded in
muscle bundles as well as between fat and
lean, was the most diffi cult carcass surface
region to decontaminate even with organicEggenberger - Solorzano et al. 2002 ; Bosilevac
et al. 2006 ). Furthermore, acetic (1.5 – 3%)
and lactic (2%) acid spraying have also
reportedly decreased populations of spoilage
bacteria of lamb or beef, such as psychrotro-
phic Gram - negative fl ora (e.g., pseudomo-
nads), lactic acid bacteria, yeasts, and
Brochothrix thermosphacta (Anderson et al.
1988 ; Dorsa et al. 1997a, 1998a, b, c ;
Koutsoumanis et al. 2004 ). The observed
reductions were higher than those achieved
by washing with cold (32 ° C) or hot (72 ° C)
water (Dorsa et al. 1998 a, b, c ). Even though
fumaric acid (1% and 1.5% at 55 ° C for 5 s)
alone or as a mixture with acetic acid has also
been found effective in reducing pathogens
on beef carcass tissue (Bell et al. 1986 ;
Podolak et al. 1996 ), it is not commercially
applied. Fumaric acid has a negative impact
on the appearance and fl avor of meat, even at
low concentrations (0.046%), while it has not
been included in the list of safe and suitable
ingredients for use in the production of meat
and poultry products (USDA - FSIS 2008c ).
The effi ciency of organic acid rinses in
reducing contamination is affected by the
type of acid, its concentration, the tempera-
ture and duration of application, the type of
microorganism and level of contamination,
the coverage of the carcass surface with the
solution, the carcass surface region, the type
of tissue (e.g., lean or adipose, frozen or
fresh tissues), and the stage of application
(Anderson et al. 1988 ; Anderson and Marshall
1989 ; Cutter and Siragusa 1994b ; Hardin et
al. 1995 ; Cutter et al. 1997 ; van Netten et al.
1997 ; Castillo et al. 2001b ; Gill and Landers
2003b ). Lactic acid (2%, 55 ° C) was found
more effective than acetic acid in reducing
inoculated E. coli O157:H7 on beef carcass
surfaces (Hardin et al. 1995 ). This may be
associated with the higher reduction of
surface pH caused by lactic acid (pKa = 4.73)
than acetic acid (pKa = 3.86), when applied
at the same concentrations. Perhaps the
higher effectiveness of lactic compared to
acetic acid also explains why spraying tem-