Chemistry Reference
In-Depth Information
to the formation of aliphatic hydrocarbons, alcohols, aldehydes and ketones. Further alcohols
react with free fatty acids forming some esters.
101, 108-110
12.5.2 Effect of enzymes on ripening of dry-cured
meat products
Dry-cured meat products need a long period of ripening in order to allow the transformation
of free amino acids and fatty acids through microbial (oxidative deaminations, decarboxyla-
tions) and/or chemical (Maillard reactions) ways to yield aromatic compounds (aldehydes,
ketones, lactones, alcohols and esters). Because long ripening time involves a high cost of
storage until a suitable matured state is reached, many attempts have been made to shorten
this period. Proteases and lipases have been used for this purpose. However, it has been
found that addition of proteinases and lipases alone is not useful in shortening the ripening
time. This is because the final flavour also depends on subsequent generation of volatile com-
pounds through lipid oxidation and amino acid catabolism. Therefore, to shorten the ripening
of sausages, it is necessary to create conditions, for example by adding an efficient starter or
by adding other types of enzymes, which stimulate formation of volatiles in a shorter time
than usual. Table 12.5 shows examples of the use of enzymes for flavour formation and for
shortening the ripening time.
The most promising method to shorten ripening time of fermented sausages has been
obtained by the incorporation of cell-free extracts from lactic acid bacteria and moulds. The
addition of cell-free extract from
Lactobacillus paracasei
sbsp.
paracasei
has been found
to accelerate the ripening and improve the sensory quality of sausages.
111
The addition of
cell-free extracts from moulds such as
Mucor racemosus
and
Penicillium aurantiogriseum
also leads to improved sensory properties of fermented sausages by increasing the generation
of ammonia and volatile compounds derived from amino acid catabolism.
112-114
Bolumar
et al
.
115-117
purified and characterized two proteinases (PrA and PrB) and two aminopepti-
dases (arginyl aminopeptidase and prolyl aminopeptidase) from cell-free extract of the yeast
strain
Debaryomyces hanseii
CECT 12 487. The enzymes were used to catalyze the hydrol-
ysis of sarcoplasmic proteins and, together with amino acid converting enzymes, to generate
ammonium and thereby increase the pH. Bolumar
et al
.
118
used above-mentioned cell-free
extract together with the extract from
Lactobacillus sakei
CECT 4808 containing high ex-
oproteolytic activity to accelerate the proteolytic pathway and thereby improve the sensory
quality of fermented meat products. By addition of these extracts the sensory quality of
fermented meat products was improved by promoting the generation of volatile compounds
derived from lipid oxidation and carbohydrate fermentation.
12.6
STRUCTURE ENGINEERING BY
CROSS-LINKING ENZYMES
Apart from the hydrolytic enzymes affecting the tenderness of meat or generation of flavour,
the functional properties of meat proteins can be modified by cross-linking enzymes. These
enzymes are used to bind fresh meat pieces together and to tailor the structural properties of
various processed meat products. The main target protein in meat for cross-linking enzymes
is the myofibrillar protein myosin. Cross-linking enzymes are generally capable of positively
affecting gelation and consequently the texture of meat gels. Potential cross-linking enzymes
