Influence of egg yolk-curdlan thermal-driven edible coating on the quality and retrogradation behavior of fried rice

Abstract

To delay the retrogradation and improve the quality of fried rice during freeze-thaw cycles (FTCs), the curdlan (CD) was added to the egg yolk liquid (EYL) to fabricate composite edible coating, leveraging their thermal drive effect. The egg yolk liquid-curdlan (EC) edible coating solutions were investigated using Fourier transform infrared spectroscopy (FTIR) and colorimeter. Results indicated that the blue shift of the egg yolk liquid and the red shift of curdlan confirms the formation of an intermolecular interaction force. Moreover, with the increase of the curdlan concentration, the chroma (C*) of the coating liquid shows a trend of initially increased and then decreased. However, the taste decreased with the increase of the gum concentration in the formula, fortunately, the difference is small at low mass concentrations (≤1%). Additionally, the application of the coating significantly improved the quality of fresh fried rice, especially the moisture content increased by nearly 3.47% and the hardness decreased by nearly 33.19% compared with the pure egg yolk group. During the freeze-thaw cycles, the coating prominently reduced the moisture loss, and delayed the increases of hardness, fluctuation of water migration, and color parameter of fried rice, especially the 1% group. Finally, it also performs well in delayed starch retrogradation after seven freeze-thaw cycles, as reflected by low values for short-range order degree (0.42, 1%), relative crystallinity (8.09%, 1.5%), and retrogradation enthalpy (2.32 J/g, 1%). This further confirms that the egg yolk liquid-curdlan thermal-driven coatings have broad prospects in starch-based food applications.