254
11 Enzymes
For example, a poly-1 → 4-alpha-l-guluronate lyase enzyme cleaves the 1 → 4
glycosidic bond of alpha-l-guluronic acids (Sil’chenko et al. 2013). This enzyme
was extracted from the mollusk Lambis sp.
11.8.5 Fish Processing: Skin and Scale Removal
Proteolytic enzymes are used in removal of skin and scales in processing of fish
food. The use of enzymes for skin removal in fish has been known for a few decades
(Amano 1962; Kim et al. 2002). Manually descaling and deskinning fish are often
time-consuming and require more man power. This process could be made faster by
treating the fish with enzymes where a batch of fish can be processed at once.
The goal of enzyme-assisted skin removal is to remove the fish skin without
damaging the muscles which are the part required for the fish food product. The
fish skin is often removed as it contains fat and in particular food preparations such
as fish fillets, the texture is undesirable. In other seafood such as squid, the removal of
the skin is necessary to improve the organoleptic properties and also improve storage.
In removal of fish skin, a combination of pepsin and carbohydrase is often used to
aid efficient removal. Lipase can be applied in the defatting of fish during processing
(Zhang and Kim 2010). This results in a less physically demanding process compared
to manual fat expression and is also milder than use of alkaline for defatting.
Proteolytic enzymes from fish are also used in the process of extracting other compounds from aquatic waste. For example, in the extraction of glycosaminoglycans
from the viscera of Nile tilapia, proteolytic enzymes are used in the deproteinization
of the tissue (Nogueira et al. 2019). GAG is also a polymer which is valued for its
anticoagulant properties and other pharmacological applications. The enzymes from
aquatic waste, either endogenous or exogenous, are also useful in obtaining other
valuable by-products from aquatic waste.
11.8.6 Fish Sauce and Fish Protein Hydrolysate Production
Fish sauce is produced from the fermentation of fish such as sardines and anchovy;
generally, fish growing in the pelagic zone of the water are less expensive catch. The
process occurs at room temperature, pH between 5.5 and 6.5 and high salinity which
is achieved by adding 20–30 weight % of salt. A mixture of endogenous enzymes is
allowed to ferment the fish and produce the sauce as the fermented by-product. The
high salinity eliminates much of the bacteria which could also ferment the fish to
produce undesirable by-products; therefore, the salinity ensures the right conditions
for the endogenous enzymes and microorganisms which will result in the production
of fish sauce. The process of fermentation takes place between 6 and 12 months at
the end of which an ambered colored solution of fish sauce and salt is obtained from
the bottom drain.
11 Enzymes
For example, a poly-1 → 4-alpha-l-guluronate lyase enzyme cleaves the 1 → 4
glycosidic bond of alpha-l-guluronic acids (Sil’chenko et al. 2013). This enzyme
was extracted from the mollusk Lambis sp.
11.8.5 Fish Processing: Skin and Scale Removal
Proteolytic enzymes are used in removal of skin and scales in processing of fish
food. The use of enzymes for skin removal in fish has been known for a few decades
(Amano 1962; Kim et al. 2002). Manually descaling and deskinning fish are often
time-consuming and require more man power. This process could be made faster by
treating the fish with enzymes where a batch of fish can be processed at once.
The goal of enzyme-assisted skin removal is to remove the fish skin without
damaging the muscles which are the part required for the fish food product. The
fish skin is often removed as it contains fat and in particular food preparations such
as fish fillets, the texture is undesirable. In other seafood such as squid, the removal of
the skin is necessary to improve the organoleptic properties and also improve storage.
In removal of fish skin, a combination of pepsin and carbohydrase is often used to
aid efficient removal. Lipase can be applied in the defatting of fish during processing
(Zhang and Kim 2010). This results in a less physically demanding process compared
to manual fat expression and is also milder than use of alkaline for defatting.
Proteolytic enzymes from fish are also used in the process of extracting other compounds from aquatic waste. For example, in the extraction of glycosaminoglycans
from the viscera of Nile tilapia, proteolytic enzymes are used in the deproteinization
of the tissue (Nogueira et al. 2019). GAG is also a polymer which is valued for its
anticoagulant properties and other pharmacological applications. The enzymes from
aquatic waste, either endogenous or exogenous, are also useful in obtaining other
valuable by-products from aquatic waste.
11.8.6 Fish Sauce and Fish Protein Hydrolysate Production
Fish sauce is produced from the fermentation of fish such as sardines and anchovy;
generally, fish growing in the pelagic zone of the water are less expensive catch. The
process occurs at room temperature, pH between 5.5 and 6.5 and high salinity which
is achieved by adding 20–30 weight % of salt. A mixture of endogenous enzymes is
allowed to ferment the fish and produce the sauce as the fermented by-product. The
high salinity eliminates much of the bacteria which could also ferment the fish to
produce undesirable by-products; therefore, the salinity ensures the right conditions
for the endogenous enzymes and microorganisms which will result in the production
of fish sauce. The process of fermentation takes place between 6 and 12 months at
the end of which an ambered colored solution of fish sauce and salt is obtained from
the bottom drain.