Characterization of egg white powder gel structure and its relationship with gel properties influenced by pretreatment with dry heat

Egg white powder (EWP) is extensively used in many segments of the food industry, which is capable of replacing traditional liquid egg materials. Dry heating plays an essential role in obtaining the excellent gelling properties of EWP during processing. The objective of this work was to better understand the gel structure of EWP and its relationship with gel properties after different pretreatment dry heating times by low-field nuclear magnetic resonance, scanning electronic microscopy and FTIR spectrometer. The obtained results showed that the strength, transparency and water holding capacity of the EWP gels were increased significantly by pretreating the EWP with dry heat. The L* value decreased significantly, while b* and the a* value of the EWP gels had little change with increasing heating time. After pretreatment with dry heat, the EWP formed a compact and microstructurally homogeneous gel with fewer large pores, and the fractal dimension of the resulting EWP gel showed an increasing trend from 2.86 (0 d) to 2.92 (21 d). The average pore size gradually decreased, which was correlated with the EWP gel properties. Furthermore, the EWP gels exhibited a significant increase in α-helix and β-sheet content as the pretreatment heating time was increased. The increase in ordered secondary structures was associated with the modified EWP gel properties. The relationship between changes in the structure and the properties of the EWP gels could be used to design various product systems.