Thermodynamic Properties and State Diagram of Gum Ghatti-Based Edible Films: Effects of Glycerol and Nisin

Pingping Zhang; Ya Zhao; Xin Zhang; Lanlan Zhu; Zhongxiang Fang; Qilong Shi

doi:10.3390/polym12020449

Thermodynamic Properties and State Diagram of Gum Ghatti-Based Edible Films: Effects of Glycerol and Nisin

Polymers (Basel). 2020 Feb 14;12(2):449. doi: 10.3390/polym12020449.

Authors

Pingping Zhang¹, Ya Zhao¹, Xin Zhang¹, Lanlan Zhu¹, Zhongxiang Fang², Qilong Shi¹

Affiliations

¹ School of Agricultural Engineering and Food Science, Shandong University of Technology, Xincun West Road, Zibo, Shandong 255000, China.
² School of Agriculture and Food, The University of Melbourne, Parkville 3010, Australia.

Abstract

In this present study, the thermodynamic and thermal properties of glycerol and nisin-incorporated gum ghatti (GG, Anogeissus latifolia)-based films were determined. The films exhibited type III isotherm behaviors. Moisture content (MC) of films was increased with increasing water activity (a_w) and decreased with higher temperature. The incorporation of glycerol and nisin increased the sorption ability of GG films. The net isosteric heat of adsorption (q_st) and differential entropy (S_d) were decreased with increasing MC, showing an exponential negative correlation between them. Spreading pressure (φ) was increased with increasing a_w, but decreased with higher temperature. This incorporation of glycerol and nisin increased the q_st, S_d and φ of the GG films. The sorption behaviors were enthalpy-driven and non-spontaneous processes. The glass transition temperature (T_g), critical MC and a_w of the films were decreased, and increased respectively with the incorporation of glycerol and nisin. This work provides a theoretical basis for the application of edible films in fresh food preservation.

Keywords: glycerol; gum ghatti; nisin; state diagram; thermodynamic properties.