fi sh protein hydrolysates prepared using alcalase had less bitter principles
as compared to those made with plant proteases like papain (Hoyle
and Merritt, 1994; Kristinsson and Rasco, 2000b). Recently hydrolysis
conditions for preparation of protein hydrolysates from freshwater fi sh
processing wastes using alcalase have been optimized (Bhaskar et al.,
2008). The fl ow-chart for preparation of fi sh protein hydrolysate using
commercial proteases is outlined in Fig. 10.3.
Heat Treatment (85°C, 20 minutes)
Cool and Centrifuge
Protein rich residue
Extract with Distilled water (1:1 w/v; 3 times)
Hydrolyze with Alcalase (Optimized Conditions)
Heat inactivate the enzyme (85°C; 20 minutes)
Fig. 10.3 Flow sheet for the production of protein hydrolysate from the visceral wastes of
Catla ( Catla catla ) using alcalase under optimized conditions . (from Bhaskar et al., 2008).
Although, alcalase is favoured by several researchers in the preparation
of fi sh protein hydrolysate (Benjakul and Morrisey, 1997; Kristinsson
and Rasco, 2000b; Bhaskar et al., 2007a, c), it requires a suitable pH for
its activity. However, pH of fi sh visceral wastes usually varies between
5.85 and 6.25 (Bhaskar and Mahendrakar, 2007; Bhaskar et al., 2007a, c).
Adjustment of pH prior and/or during hydrolysis, although is common,
is not industrially desirable as the added acid/alkali results in unwanted
inorganic mass (salt) that may result in undesirable effects and/or may be
diffi cult to remove later in the hydrolysate recovery process (Aspmo et al.,
2005). In this regard, neutral proteases of microbial origin look promising
as natural ( in situ ) pH of the visceral waste itself can be utilized to prepare
protein hydrolysates (Guerard et al., 2002; Dauksas et al., 2005; Nilsang et
al., 2005; Dumay et al., 2006; Bhaskar and Mahendrakar, 2008).