OPTIMIZATION OF THE PRODUCTION OF HYDROLYSATES FROM GRASS CARP (CTENOPHARYNGODON IDELLA) SKIN USING ALCALASE

Abstract

ABSTRACT Protein hydrolysate was produced from grass carp skin using Alcalase. Hydrolysis conditions were optimized by using a response surface methodology (RSM). A model equation was proposed with regard to effects of temperature (T), pH, enzyme/substrate (E/S) ratio (%v/w of minced skin) and time (t) on degree of hydrolysis (%DH). The optimum values for T, pH, E/S ratio and t were found to be 59.74C, 8.25, 1.70% and 83.83 min, respectively. Regression coefficients indicated that all linear forms T, pH, t and E/S ratio plus one quadratic form t2 and one cross-product interaction T · t were significant (α = 0.05). The model showed a good fit in experimental data because 90.7% of the variability within the range of values studied could be explained by it. The freeze-dried hydrolysate contained high protein content (90.8%). The hydrolysate produced was highly water-soluble with good water-holding, oil-binding and emulsifying properties. Thus, the production of a hydrolysate with desired functional properties is possible from grass carp skin using Alcalase. PRACTICAL APPLICATIONS Considerable amounts of protein-rich by-products from seafood processing plants are discarded without any attempt to carry out recovery. The preference in many Western countries for bone-free fillets necessitates the removal of flesh from fish, and a substantial amount of original weight is considered a waste, of which the skin is inclusive. It would be of great interest to put these by-products that are high in protein to use in human foods instead of in fish meals for animal feed. Enzymatic hydrolysis of food proteins generally results in profound changes in the functional properties of proteins treated. The choice of substrate, the protease enzyme employed and the degree of hydrolysis can greatly affect the physicochemical properties of the resultant hydrolysate. Through the control of the process parameters such as pH, time and enzyme/substrate ratio, it is possible to produce hydrolysates whose components may present some interesting properties. Fish protein hydrolysates have numerous applications, particularly in the food and pharmaceutical industries.