Functional properties of grass carp (ctenopharyngodon idella), Nile perch (lates niloticus) and Nile tilapia (oreochromis niloticus) skin hydrolysates

Abstract

The influence of using an endo-peptidase (alcalase) on the functional properties of hydrolysis products from Nile perch, Grass carp, and Nile tilapia skin was studied. Reaction conditions were controlled at pH 8.25, 60°C, and the enzyme was added on the basis of standard activity units at an enzyme to substrate ratio of 1.7 g/100 g protein. The reaction was allowed to proceed for 85 min and enzyme was inactivated by heat. The soluble protein fractions were recovered and lyophilized. All freeze-dried fish skin hydrolysates powders had a light yellow color and contained up to 90% protein. Nitrogen solubility varied from 95.93 to 98.72% and was not significantly different at 5% probability level. The water and oil holding capacities of the skin hydrolysates were good in the range of 2.8 to 3.2 mL/g and 3.4 to 3.8 mL/g, respectively. Emulsification capacity varied from 11.3 to 21 mL/0.5 g with Nile perch skin hydrolysate having the highest score while Nile tilapia skin hydrolysate was the lowest. Grass carp skin hydrolysate was not able to form stable foam, unlike the Nile perch and Nile tilapia skin hydrolysate. Alcalase treated freshwater fish skin exhibited satisfactory functional properties hence may play an important role as an ingredient in the food and pharmaceutical industry.