Food Biochemistry and Food Processing

14 Biochemistry of Processing Meat and Poultry 327

LIPOLYSIS

Lipolysis makes an important contribution to the
quality of meat products by the generation of free
fatty acids, some of which have a direct influence on
flavor, and others that, with polyunsaturations, may
be oxidized to volatile aromatic compounds, acting
as flavor precursors. The general scheme for lipoly-
sis in muscle and adipose tissue is shown in Figure
14.10. In addition, the breakdown of triacylglycerols
affects the texture of the adipose tissue, and an ex-
cess of lipolysis/oxidation may contribute to the
development of rancid aromas or yellowish colors in
fat (Toldrá 1998).

LIPOLYSIS INAGEDMEAT ANDCOOKEDMEAT
PRODUCTS

The relative amounts of released free fatty acids
depends not only on the enzyme preference, but also
on many other factors such as raw materials (espe-
cially affected by feed composition), type of pro-
cess, and extent of cooking (Toldrá 2002). The gen-
eration rate observed during in vitro incubations of
muscle lipases with pure phospholipids is the fol-
lowing (in order of importance): linoleic oleic 

linolenic palmitic stearic arachidonic acid

(Toldrá, unpublished results). Lipolysis may also

vary depending on the type of muscle, as oxidative

and glucolytic muscles exhibit different lipase activ-

ity (Flores et al. 1996). The generation of free short-

chain fatty acids is very low due to the lack of ade-

quate substrate (Motilva et al. 1993b). The physical

and chemical conditions in the muscle and adipose

tissue, especially during cooking, may affect the

enzyme activity (see Tables 14.3 and 14.4). The evo-

lution of muscle lipases during ageing of pork meat

is shown in Figure 14.11.

LIPOLYSIS INFERMENTEDMEATS

Depending on the raw materials, type of product,

and processing conditions, the degree of contribu-

tion of endogenous and microbial origin lipases will

vary. The relative importance of both enzyme sys-

tems has been checked with mixtures of antibiotics

and antimycotics used in sterile meat model systems

(Molly et al. 1997). The results showed a minimal

effect of antibiotics, and it was concluded that lipol-

ysis is mainly brought about by muscle and adipose

tissue lipases (60–80% of total free fatty acids gen-

erated), even though some variability might be

Figure 14.10.General scheme of lipolysis during the processing of meat and meat products.