Food Biochemistry and Food Processing (2 edition)

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18 Biochemistry of Fermented Meat 341

may affect some of these textural characteristics, but, in general,

the final texture of the sausage will mainly depend on the extent

of drying (Toldra et al. 2004). ́

Flavor

Little or no flavor is usually detected before meat fermentation,

although a large number of flavor precursors are present. As fer-

mentation and further ripening/drying progress, the combined

effect of endogenous muscle enzyme and microbial activity pro-

duces a high number of nonvolatile and volatile compounds

with sensory impact. The longer the process, the more the ac-

cumulation of these compounds is increased and their sensory

impact enhanced. Although not so important as in meat cooking,

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 fer-

mented meats are summarized in Table 18.5. Sour taste, mainly

resulting from lactic acid generation through microbial glycoly-

sis, 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

activities, usually present in yeasts and molds, reducing the in-

tensity of the acid taste. Salty taste is usually perceived as a

direct taste from salt addition. ATP (adenosine triphosphate)-

derived compounds such as inosine monophosphate and guano-

sine monophosphate exert some taste enhancement, while hy-

poxanthine contributes to bitterness. Other taste contributors are

those compounds resulting from protein hydrolysis. The gener-

ation 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 in Section

“Aroma”.

Aroma

The origin of aroma mainly depends on the ingredients and

processing conditions. Different pathways are responsible for

the formation of volatile compounds with aroma impact (Table

18.6). As mentioned previously, proteolysis gives rise to a large

amount of small peptides and free amino acids. Microorganisms

can convert the amino acids leucine, isoleucine, valine, pheny-

lalanine, and methionine to important sensory compounds with

low threshold values. Some of the most important are branched

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

Table 18.6.Quality Aspects: Generation of Desirable Volatile Compounds Contributing to Aroma in Fermented

Meats.

Group of Compounds

Main Representative

Compounds Routes of Generation Main Aroma

Expected

Contribution

Aliphatic aldehydes Hexanal, pentanal,

octanal, etc.

Oxidation of unsaturated fatty acids Green High

Strecker aldehydes 2- and

3-methylbutanal,

etc.

Strecker degradation of free amino

acids

Roasted cocoa,

cheesy-green

High

Branched-chain acids 2- and 3-methyl

butanoic acid

Secondary products of previous

Strecker degradation

Sweaty Medium

Alcohols Ethanol, butanol, etc. Oxidative decomposition of lipids Sweet, alcohol, etc. Low

Ketones 2-pentanone,

2-heptanone,

2-octanone, etc.

Lipid oxidation Ethereal, soapy Medium

Sulfides Dimethyldisulfide Strecker degradation of

sulfur-containing amino acids

(methionine)

Dirty socks Low

Esters Ethyl acetate, ethyl

2-methyl-

butanoate

Interaction of carboxylic acids and

alcohols

Pineapple, fruity High

Hydrocarbons Pentane, heptane, etc. Lipids autoxidation Alkane Very low

Dicarbonyl products Diacetyl, acetoin,

acetaldehyde

Pyruvate microbial metabolism Butter Low

Nitrogen compounds Ammonia Deamination, deamidation Ammonia Variable, depends

on growth of

yeasts and molds

Source: Adapted from Viallon et al. (1996), Flores et al. (1997), Stahnke (2002), Toldr ́a (2002) and Talon et al. (2002).