Hydrolysis Process Optimization and Functional Characterization of Yak Skin Gelatin Hydrolysates

Hui Yang,Hongji Zhu,Xiangyu He,Shan He,Qianqian Song,Li Tian,Shunyi Song,Yanting Xue,Jiaheng Liu,Lei Zhang

doi:10.1155/2019/9105605

Abstract

Yak (Bos grunniens) is an animal mainly living on the Tibetan Plateau. Yak skin is a valuable resource that is wasted in the meat production process. This study aimed to prepare yak skin gelatin hydrolysates (YSGH) from yak skin through enzymatic hydrolysis and investigate functional characterization of YSGH. We showed that trypsin was more effective than neutrase, papain, and pepsin in increasing the degree of hydrolysis (DH) of YSGH. The conditions of enzymatic hydrolysis were optimized using central composite design (CCD) and response surface method (RSM), and the highest DH value of 31.96% was obtained. We then analyzed the amino acid compositions and molecular weight distribution of peptides in YSGH. The obtained YSGH exhibited certain antioxidant activity and excellent ACE-inhibitory activity (IC50 = 0.991 mg/mL). In addition, the solubility (98.79%), emulsification, and foaming properties of YSGH developed here were also evaluated. With these physicochemical and biological functions, YSGH had potential applications in food, pharmaceuticals, and cosmetics as an ingredient.

Highlights

Gelatin hydrolysates can be obtained by hydrolysis of gelatin from animal sources such as pigs [1], bovine [2], and fish [3]
Yak skin was soaked in water, and its impurities and hair were cleaned and removed, chopped into 0.5 × 0.5 cm2 and stored at − 20°C. e pieces of skin were mixed with n-butyl alcohol solution (1 : 10, w/v) at a ratio of solid to solution 1 : 20 (w/v) to remove fat and noncollagen protein. e mixture was stirred for 24 h at 4°C, washed with distilled water until neutral pH
Preparation of Yak Skin Gelatin. e composition of gelatin was related to the type of animal and the environment in which the animal grows. e flowchart of technological process was shown in Figure 1. e obtained gelatin contained protein (96.58%), lipid (1.27%), and ash (1.90%). e gelatin yield reached 52.97%, which is much higher than the reported extraction rates of many other animal gelatins [28,29,30]. e reason might be that yak skin contained more proteins and less lipids since yaks live in high altitudes with extremely cold climates [31]. us, the higher gelatin yield ensured the feasibility of its use in preparing gelatin hydrolysates

Summary

Introduction

Gelatin hydrolysates can be obtained by hydrolysis of gelatin from animal sources such as pigs [1], bovine [2], and fish [3]. Gelatin hydrolysates have been widely used in the production of pharmaceuticals and foods in the United States and Europe and have the potential for several advanced applications, such as smart drug delivery carriers for cancer therapy [10] and a new type of wound dressing [11]. It was found that oral intake of gelatin hydrolysates has beneficial effects on skin recovery, including supporting wound closure and reducing skin wrinkles [12]. Oral intake of gelatin hydrolysates can increase bone mass and prevent osteopenia [13]. In these previous studies, the functional properties of gelatin hydrolysates depended on the source of gelatin and the types of enzymes and the enzymolysis conditions [14]

Objectives

Methods

Results