Biology Reference
In-Depth Information
from shrimp waste by lactic acid fermentation (Hall and Silva, 1992; Rao
et al., 2000).
Apart from fermentation, several enzymes of microbial origin have
also been employed for the production of protein hydrolysates from fi sh
industry wastes (Benjakul and Morrissey, 1997; Kim et al., 2001; Lian et
al., 2005; Nilsang et al., 2005; Ramirez, 2007; Bhaskar et al., 2008; Bhaskar
and Mahendrakar, 2008). Traditional methods for preparation of autolytic
hydrolysate like fi sh silage exploit the endogenous enzymes and it is
rather diffi cult to control the autolysis by endogenous enzymes due to
several factors including fi sh species and seasonality as well as the type
and amount of enzymes (Sikoroski and Naczk, 1981). Alternatively,
enzymatic proteolysis can be employed to recover biomass from fi sh
visceral mass and results in a soluble product generally referred to as
fi sh protein hydrolysate (Guerard et al., 2002). The benefi t of hydrolyzing
fi sh proteins, to make functional protein ingredients and nutritional
supplement is a more recent technology, although the fi rst commercially
available protein hydrolysate appeared in the late 1940s. In spite of the
production being massive world wide, proper control of the process and
the exact mechanism behind protein hydrolysis is not fully understood
(Kristinnson and Rasco, 2000c).
Application of Exogenous Enzymes
Addition of exogenous enzymes could make the hydrolytic process more
controllable, apart from hastening it, thereby making it reproducible.
Several factors such as pH, incubation period, enzyme: substrate ratio
and temperature infl uence enzymatic activity (Viera et al., 1995; Liaset
et al., 2000; Guerard et al., 2002). Proteolytic enzymes from plants and
microorganisms have been found to be suitable to produce fi sh protein
hydrolysate (Benjakul and Morrisey, 1997; Guerard et al., 2001; Nilsang
et al., 2005). Acid proteases, even though is better for microbial growth
prevention, have only low protein yield and thus, milder enzymes at
neutral and slightly alkaline conditions have been used more frequently
(Kristinsson and Rasco, 2000c). Enzymes used to produce fi sh protein
hydrolysate have at least one common characteristic; they should be
food grade and if they are of microbial origin, the producing organism
has to be non-pathogenic. The choice of substrate, protease employed
and the degree to which the protein gets hydrolyzed generally affect the
physico-chemical properties of the resulting hydrolysates (Mullaly et al.,
1995). Alcalase—an alkaline bacterial protease produced from
Bacillus
licheniformis
, has been proven to be one of the best enzymes used in the
preparation of fi sh protein hydrolysate (Hoyle and Merritt, 1994; Shahidi
et al., 1995; Benjakul and Morrisey, 1997; Dufosse et al., 1997; Kristinsson
and Rasco, 2000a, b; Guerard et al., 2001). Further, it has been reported that
