32 Chapter 2
Hambrecht et al. (2005) reported that high
stress conditions (long transport, short
lairage) decreased muscle glycolytic poten-
tial and increased plasma lactate, cortisol,
muscle temperature, rate of pH decline, ulti-
mate pH, and b * values (yellowness) of
pork. Other color measures were unaffected
by high stress but water - holding properties
were impaired. Because supplemental dietary
magnesium is related to postmortem glyco-
gen breakdown of lactic acid and concomi-
tant muscle pH decline, it has been shown
to help offset damage to color and water -
holding capacity that result from the stress
involved in transport and handling (Frandson
and Spurgeon 1992 ). Feeding swine magne-
sium during the fi nishing phase results in
higher initial and/or ultimate muscle pH
values and a decrease in the incidence of
PSE (D ’ Souza et al. 1998 ; Swigert et al.
2004 ).
Flavor
Meaty Flavor
“ Flavor ” results from the combination of the
basic tastes (sweet, sour, bitter, salt, umami)
derived from water - soluble compounds and
odors derived from a variety of substances
present in the raw meat. Flavor - and odor -
active volatiles include alcohols, aldehydes,
aromatic compounds, esters, ethers, furans,
hydrocarbons, ketones, lactones, pyrazines,
pyridines, pyrroles, and sulfi des (Shahidi
1994 ). The relationship between some of the
more common volatiles and their respective
fl avors is shown in Table 2.1.
The lipids present in muscle tissue (sub-
cutaneous fat, intramuscular fat, intermuscu-
lar fat, intramyocellular lipid, and structural
phospholipids) at slaughter serve as a source
of many of these fl avor constituents. These
lipids are composed of fatty acids that may
be saturated, unsaturated and/or methyl -
branched (Fig. 2.2 ). They may be derived
directly from the diet, produced as the result
of biohydrogenation of dietary lipids, or via
endogenous synthesis. Increased marbling,
because of the increased amount of fat avail-
able for formation of fl avor compounds, has
traditionally been considered to have a rela-
tively large impact on the ultimate fl avor of
the meat product.
“ Meaty fl avor, ” the generic background
fl avor of all types of red meat, is associated
with the lean portions of meat. Phospholipids
(0.5 – 1% of the lean tissue) contain a high
proportion of fatty acids with four or more
double bonds (C18:4, C20:4, C20:5, C22:5,
C22:6; Table 2.2 ) that are susceptible to
oxidation and likely to make specifi c fl avor
contributions to the meat (Elmore et al.
1999 ). Endogenous antioxidant enzymes,
especially catalase and GSH - Px, can poten-
tially delay the onset of oxidative rancidity
(Pradhan et al. 2000 ). Some meat processing
operations reduce the activity of these
systems (Decker and Mei 1996 ). Of the 60 -
plus compounds that contribute specifi cally
to “ meaty ” aromas, most are sulfur - or car-
bonyl - containing compounds (Shahidi 1994 ).
Phospholipids are also the source of several
sulfi des that are generated when they react
with cysteine and/or ribose to produce mild,
slightly meaty - fl avor/odor compounds, such
as 2 - methyl - 3 - [methylthio]thiophene (Rowe
2002 ).Species - Specifi c Flavor
Species - specifi c fl avor has traditionally
been associated with the lipid portion
of meat. It may result from quantitative dif-
ferences of several compounds (3,5 - dimethyl -
1,2,4,trithiolane, 2,4,6 - trimethylperhydro -
1,3,5 - dithiazine, mercaptothiophenes,
mercaptofurans; Shahidi et al. 1994 ). A beef -
like aroma compound, 12 - methyltridecanal,
is an important contributor to species fl avor
(Mottram et al. 1982 ). It occurs in much
smaller amounts in species other than beef.
Other species - specifi c fl avor compounds
include 2 - methyl - 3 - [methyl] - furan and