Multiscale structure changes and mechanism of polyphenol-amylose complexes modulated by polyphenolic structures.

This study was designed to investigate the effect of polyphenolic structure on the interaction strength and process between polyphenols (gallic acid (GA), epigallocatechin gallate (EGCG) and tannic acid (TA)) and amylose (AM). The results of Fourier transform infrared spectroscopy, isothermal titration calorimetry, X-ray photoelectron spectroscopy and molecular dynamic simulation (MD) suggested that the interactions between the three polyphenols and AM were noncovalent, spontaneous, low-energy and driven by enthalpy, which would be enhanced with increasing amounts of pyrogallol groups in the polyphenols. The results of turbidity, particle size and appearance of the complex solution showed that the interaction process between polyphenols and AM could be divided into three steps and would be advanced by increasing the number of pyrogallol groups in the polyphenols. At the same time, MD was intuitively employed to exhibit the interaction process between amylose and polyphenols, and it revealed that the interaction induced the aggregation of amylose and that the agglomeration degree of amylose increased with increasing number of pyrogallol groups at polyphenols. Last, the SEM and TGA results showed that TA/AM complexes had the tightest structure and the highest thermal stability (TA/AM˃EGCG/AM˃GA/AM), which could be attributed to TA having five pyrogallol groups.

Effect of polyphenolic structure and mass ratio on the emulsifying performance and stability of emulsions stabilized by polyphenol-corn amylose complexes.

O/W emulsions stabilized by polyphenol/amylose (AM) complexes with several polyphenol/AM mass ratios and different polyphenols (gallic acid (GA), epigallocatechin gallate (EGCG) and tannic acid (TA)) were prepared by a high-intensity ultrasound emulsification technique. The effect of the pyrogallol group number of polyphenols and the mass ratio of polyphenols/AM on polyphenol/AM complexes and emulsions was studied. The soluble and/or insoluble complexes gradually formed upon adding polyphenols into the AM system. However, insoluble complexes were not formed in the GA/AM systems because GA has only one pyrogallol group. In addition, the hydrophobicity of AM could also be improved by forming polyphenol/AM complexes. The emulsion size decreased with increasing pyrogallol group number on the polyphenol molecules at a fixed ratio, and the size could also be controlled by the polyphenol/AM ratio. Moreover, all emulsions presented various degrees of creaming, which was restrained by decreasing emulsion size or the formation of a thick complex network. The complex network was enhanced by increasing the ratio or pyrogallol group number on the polyphenol molecules, which was because the increasing number of complexes was adsorbed onto the interface. Altogether, compared to GA/AM and EGCG/AM, the TA/AM complex emulsifier had the best hydrophobicity and emulsifying properties, and the TA/AM emulsion had the best emulsion stability.