Morphology and Rheology of a Cool-Gel (Protein) Blended with a Thermo-Gel (Hydroxypropyl Methylcellulose)

Zhili Ji,Weiping Jin,Qingfei Duan,Song Miao,Hongsheng Liu,Long Yu,Wangyang Shen

doi:10.3390/foods11010128

Abstract

This study investigates the morphological and rheological properties of blended gelatin (GA; a cooling-induced gel (cool-gel)) and hydroxypropyl methylcellulose (HPMC; a heating-induced gel (thermo-gel)) systems using a fluorescence microscope, small angle X-ray scattering (SAXS), and a rheometer. The results clearly indicate that the two biopolymers are immiscible and have low compatibility. Moreover, the rheological behavior and morphology of the GA/HPMC blends significantly depend on the blending ratio and concentration. Higher polysaccharide contents decrease the gelling temperature and improve the gel viscoelasticity character of GA/HPMC blended gels. The SAXS results reveal that the correlation length (ξ) of the blended gels decreases from 5.16 to 1.89 nm as the HPMC concentration increases from 1 to 6%, which suggests that much denser networks are formed in blended gels with higher HPMC concentrations. Overall, the data reported herein indicate that the gel properties of gelatin can be enhanced by blending with a heating-induced gel.

Highlights

Gelatin, derived from the partial hydrolysis of collagen, has a wide range of application in the food, pharmaceutical, cosmetic, and photographic fields [1,2,3,4]
The gelatin-rich lower layer was in the gel state, whereas the hydroxypropyl methylcellulose (HPMC)-rich upper layer was in a liquid-like state
The gelation and phase behaviors of blended gelatin and HPMC systems were assessed by analyzing the phase diagram of these blends

Summary

Introduction

Gelatin, derived from the partial hydrolysis of collagen, has a wide range of application in the food, pharmaceutical, cosmetic, and photographic fields [1,2,3,4]. The food products made from gelatin gel are commonly consumed by children and adults due to their special texture and mouthfeel [5]. Considering its thermal reversible property, gelatin gel can melt at a relatively low temperature (melt-in-mouth), which renders it the preferred gelling agent in yoghurt products, sugar confectioneries, and the coating films of nuts [6,7,8,9,10]. Under certain conditions, the gel strength, gelling temperature, and gel thermal stability of gelatin might be too low. The hot weather in summer destroys gelatin gels due to their weak gel thermal stability. The consumers of these gels may experience an unpleasant impression and poor taste. The question of how to improve the gelatinous properties of gelatin has attracted great attention, and research efforts have been focused on using other food hydrocolloids, such as starch and carrageenan, to improve these properties, the thermostability of gelatin under relatively high temperatures

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Results

Conclusion