Effect of Thermal Treatment on the Physicochemical Properties of Emulsion Stabilized by Gelatin from Black Tilapia ( Ore
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ORIGINAL ARTICLE
Effect of Thermal Treatment on the Physicochemical Properties of Emulsion Stabilized by Gelatin from Black Tilapia (Oreochromis mossambicus) Skin Chek-Chuan Tan 1
&
Alias A. Karim 1 & U. Uthumporn 1 & Farid. C. Ghazali 2
Received: 13 February 2020 / Accepted: 27 May 2020 # Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract This study investigated the influence of thermal treatment (30 °C to 110 °C, 30 min) on the physicochemical and rheological properties of an emulsion stabilized by black tilapia (Oreochromis mossambicus) skin at pH 4. The protein pattern of tilapia gelatin did not have any significant difference after the gelatin was heated within a temperature range of 30 °C to 70 °C. However, at 90 °C and 110 °C, denaturation occurred where α-, β- and γ-chains of the gelatin were degraded, leading to a concomitant increase in low molecular peptides. The emulsion stability was investigated through a particle size analyzer, zeta potential, microscopic observation and creaming index. The gelatin emulsion was physically stable at 30 °C to 70 °C with a mean droplet size of less than 13 μm. When the heating temperature was increased to 90 °C and 110 °C, the emulsion showed a pronounced increase in droplet size due to coalescence. The gelatin emulsion heated at 90 °C and 110 °C also displayed instability against creaming after storage at room temperature for 7 days. As the heating temperature increased, the gelatin emulsion exhibited a decrease in apparent viscosity and the flow behavior changed from shear thinning to Newtonian. The rheological data also showed that the storage modulus (G′) of emulsion became more frequency dependent as the heating temperature increased, indicating weak droplet interactions. The tilapia gelatin emulsion was physically unstable when subjected to thermal treatment above 70 °C. The data reported in this study provides useful insight into the formulation of acidic food emulsions that require thermal treatment. Keywords Gelatin . Tilapia . Temperature . Emulsion . Rheology
Introduction Proteins are food biopolymers that have been widely used as emulsifiers in the food industry due to their amphiphilic
* Alias A. Karim [email protected] Chek-Chuan Tan [email protected] U. Uthumporn [email protected] Farid. C. Ghazali [email protected] 1
Food Biopolymer Research Group, Food Technology Division, School of Industrial Technology, Universiti Sains Malaysia, 11800 USM, Penang, Malaysia
2
School of Health Sciences, Universiti Sains Malaysia, Health Campus, 16150 Kubang Kerian, Kelantan, Malaysia
character which allows them to adsorb into the oil-water interface [1]. Upon adsorption, they form a viscoelastic film that resists mechanical stresses, and provides electrostatic as well as steric stabilization [2]. However, the stability of proteinbased emulsions is very susceptible to pH change as electrostatic repulsions play an important role in preventing droplet aggregation [1]. Therefore, emulsion droplets tend to aggregate when a protein-stabilized emuls
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