Food Biochemistry and Food Processing

306 Part III: Muscle Foods

are characterized by a greater peptidase to pro-
teinase ratio and a higher lipase, dipeptidylpeptidase
IV, and pyroglutamyl aminopeptidase activity. On
the other hand, the enzyme activity in light pigs (7–
8 months old) shows two groups. The larger one is
higher in moisture content and cathepsins B and B

L and low in peptidase activity, while the minor
one is intermediate in cathepsin B activity and high
in peptidase activity (Toldrá et al. 1996a). In gener-
al, there is a correlation between the moisture con-
tent and the activity of cathepsin B and B
L (Par-
olari et al. 1994). So, muscles with higher moisture
content show higher levels of cathepsin B and B
L
activity. This higher cathepsin activity may produce
an excess of proteolysis in processed meat products
with long processing times (Toldrá 2002).
A minor effect of sex is observed. Meats from
barrows contain more fat than those from gilts. They
present higher marbling, and the subcutaneous fat
layer is thicker (Armero et al. 1999a). In the case of
muscle enzymes, only very minor differences have
been found. Sometimes, meats from entire males

may give some sexual odor problems due to high

contents of androstenone or escatol.

EFFECT OF THETYPE OFFEED

A great research effort has been exerted since the

1980s for the manipulation of the fatty acid compo-

sition of meat, to achieve nutritional recommenda-

tions, especially an increase in the ratio between

polyunsaturated and saturated fatty acids (PUFA:

SFA ratio). More recently, nutritionists recommend

that PUFA composition should be manipulated

towards a lower n-6:n-3 ratio.

Fats with a higher content of PUFA have lower

melting points that affect the fat firmness. Softer fats

may raise important problems during processing if

the integrity of the muscle is disrupted by any me-

chanical treatment (chopping, mincing, stuffing, etc.).

The major troubles are related to oxidation and gen-

eration of off-flavors (rancid aromas) and color dete-

rioration (trend towards yellowness in the fat)

(Toldrá and Flores 2004).

Figure 13.8.Typical postmortem pH drop of normal, PSE, and DFD pork meats (Toldrá, unpublished).