Characterizations of Gelatin from the Skin of American Bullfrog (Rana catesbeiana) as Affected by Extraction Temperature

Weibo Zhang,Chong Chen,Ziyu Huang,Pengjie Wang

doi:10.3390/su13084390

Abstract

We investigated the effect of extraction temperature on the gel properties of gelatin from the skin of the American bullfrog (Rana catesbeiana) and the mechanisms. The textural and rheological properties of bullfrog gelatin extracted at 45 °C (G45), 55 °C (G55), and 65 °C (G65) were measured. The molecular weight distributions, microstructures, and amino acid compositions of the bullfrog gelatins were also determined. G45, G55, and G65 had gel strengths of 272.1, 225.6, and 205.8 g and hardness values of 28.1, 24.0, and 22.5 N, respectively. The gelling temperatures ranged from 19.3 to 23.9 °C, and the melting temperatures ranged from 28.9 to 31.5 °C. All the results were compared with those of commercial porcine gelatin. We propose that the higher gel strength of G45 with a higher band intensity of α2-chains compared with G55 and G65 was more likely to form ordered and strong cross-links. The gelatin extracted at a lower temperature (G45) had a finer gel structure, suggesting that it would be more difficult to disrupt by applied force. Gelatin extracted at a lower temperature demonstrated better properties with α2-chains and a fine gel structure. These results provide basic information on the extraction of American bullfrog skin gelatin for industrial applications.

Highlights

The results were consistent with those of Nagarajan et al [22] and Kittiphattanabawon et al [28], who reported that gelatin yield increased as the extraction temperature increased
As the extraction temperature increases, gelatin undergoes more helix-to-coil transitions and becomes easier to extract into the water, leading to a higher yield [30]
The present study investigated the influence of the extraction temperature on the gel properties of bullfrog skin gelatin

Summary

Introduction

Gelatin is a fibrous protein hydrolyzed from a collagen that is mainly derived from the skin, connective tissues, and bones of animals [1]. Gelatin has been widely used as a stabilization, gelation, and emulsion agent in food and non-food industries [2,3]. The world usage of gelatin is about 200,000 metric tons yearly [4], which is predominantly manufactured from the skin and bones of pigs and cows. Chicken skin [6], chicken deboner residue [7], duck feet [8], camel skins [9], goat skin [10], cod fish skin [11,12], salmon fish skin [13], and shark byproducts [14] as additional sources have been tapped for gelatin extraction in attempts to increase safety

Objectives

Results

Conclusion