Food Biochemistry and Food Processing

28 Biochemistry of Fermented Meat 653

drops. Nitrate reductase, which is present in Micro-
coccaceae, reduces nitrate to nitrite, which is after-
wards further reduced to nitric oxide, which can
react with myoglobin. Oxidative discoloration con-
sists in the conversion of nitrosylmyoglobin to ni-
trate and metmyoglobin, which affects the oxidative
stability because of the prooxidant effect of ferric
heme.

TEXTURE

The consistency of fermented meats is initiated with
the salt addition and pH reduction. The water-binding
capacity of myofibrillar proteins decreases as pH
approaches the proteins’ isoelectric point and releas-
es water. The solubility of myofibrillar proteins is
also reduced, with a trend towards aggregation and
coagulation, forming a gel. The consistency of this
gel increases with water loss during drying. So,
there is a continuous development of textural char-
acteristics such as firmness, hardness, and cohesive-
ness of meat particles during drying (Toldrá 2002).
The meat:fat ratio may affect some of these textural
characteristics, but in general, the final texture of the
sausage will mainly depend on the extent of drying
(Toldrá et al. 2004).

FLAVOR

Little or no flavor is usually detected before meat
fermentation, although a large number of flavor pre-
cursors are present. As fermentation and further

ripening/drying progresses, the combined effect of

endogenous muscle enzyme and microbial activity

produces a high number of nonvolatile and volatile

compounds with sensory impact. The longer the

process, the more the accumulation of these com-

pounds is increased and their sensory impact en-

hanced. Although not so important as in meat cook-

ing, some compounds with sensory impact may be

produced through further chemical reactions. The

addition of spices also has an intense contribution to

specific flavors.

Taste

The main nonvolatile compounds contributing to

taste of fermented meats are summarized in Table

28.5. Sour taste, mainly resulting from lactic acid

generation through microbial glycolysis, is the most

relevant taste in fermented meats. Sourness is also

correlated with other microbial metabolites such as

acetic acid. Ammonia may be generated through

deaminase and deamidase activity, usually present

in yeasts and molds, reducing the intensity of the

acid taste. Salty taste is usually perceived as a direct

taste from salt addition. ATP-derived compounds

such as inosine monophosphate and guanosine mono-

phosphate exert some taste enhancement, while hy-

poxanthine contributes to bitterness. Other taste con-

tributors are those compounds resulting from protein

hydrolysis. The generation and accumulation of

small peptides and free amino acids contribute to

taste perception, which increases with the length of

process. Some of these small peptides (e.g., leucine,

isoleucine, and valine) also act as aroma precursors,

as described below.

Aroma

The origin of aroma mainly depends on the ingredi-

ents and processing conditions. Different pathways

are responsible for the formation of volatile com-

pounds with aroma impact (Table 28.6). As men-

tioned above, proteolysis originates a large amount

of small peptides and free amino acids. Microorgan-

isms can convert the amino acids leucine, isoleu-

cine, valine, phenylalanine, and methionine to im-

portant sensory compounds with low threshold

values. Some of the most important are branched

aldehydes such as 2- and 3-methylbutanal and 2-

methylpropanal, branched alcohols, acids such as

Figure 28.8.Picture of a typical small-diameter
salchichón, showing its cross section.