Fish Scale Valorization by Hydrothermal Pretreatment Followed by Enzymatic Hydrolysis for Gelatin Hydrolysate Production

Yiqi Zhang,Qing Shen,Zhiyuan Dai,Dan Tu

doi:10.3390/molecules24162998

Abstract

Protein hydrolysates from fish by-products have good process suitability and bioavailability in the food industry. The objective of this work was to develop a method for protein recovery from fish scales and evaluate the hydrolysis of the scale protein. The effect of the hydrothermal process on protein recovery, degree of hydrolysis (DH) and structural properties of the hydrolysates was investigated. Results showed that hydrothermal treatment could enhance protein recovery of tilapia scales without demineralization and dramatically improve the DH of the hydrolysates. The hydrothermal treated scales showed a better protein recovery (84.81%) and DH (12.88%) and released peptides more efficiently than that of the conventional treated samples. The obtained gelatin hydrolysates mainly distributed in the range of 200–2000 Da with an angiotensin I-converting enzyme (ACE) IC50 value of 0.73 mg/mL. The ACE inhibitory activity of gelatin hydrolysates was stable under high temperature, pH and gastrointestinal proteases. Hydrothermal treatment followed by enzymatic hydrolysis offers a potential solution for preparation of gelatin hydrolysates for food ingredients from fish processing by-products.

Highlights

Gelatin is widely used in biomedical, cosmetic, leather, food and pharmaceutical industries [1,2].Fish gelatin has received increasing attention, because of the safety and religious concern of the mammalian analogue [3]
The obtained gelatin hydrolysates mainly distributed in the range of 200–2000 Da with an angiotensin I-converting enzyme (ACE) IC50 value of 0.73 mg/mL
The ACE inhibitory activity of gelatin hydrolysates was stable under high temperature, pH and gastrointestinal proteases

Summary

Introduction

Gelatin is widely used in biomedical, cosmetic, leather, food and pharmaceutical industries [1,2].Fish gelatin has received increasing attention, because of the safety and religious concern of the mammalian analogue [3]. Gelatin is widely used in biomedical, cosmetic, leather, food and pharmaceutical industries [1,2]. The nutritional value of gelatin is quite low for humans due to the lack of some essential amino acids, once it is hydrolyzed, gelatin hydrolysates have good process suitability and bioavailability, making them potential sources for value-added foods [7,8]. Gelatin is extracted from raw materials by a chemical pretreatment with dilute acid or alkali [1], which destabilizes the triple-helix through a disruption in hydrogen bonding and some covalent cross-links, enhancing protein solubilization. The overall extraction efficiency of gelatin is typically low, limiting industrial output [9]. The conventional methods used for the preparation of gelatin hydrolysates are generally reactant-, cost- and time-consuming and Molecules 2019, 24, 2998; doi:10.3390/molecules24162998 www.mdpi.com/journal/molecules

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