Hydrogel with the network structure fabricated by anthocyanin–gelatin crosslinking and improved mineral encapsulation ability

Summary In this study, four polyphenols (tea polyphenol, procyanidin, anthocyanin and gallic acid) were applied to crosslink with gelatin (G), in order to explore the crosslinking mechanisms of polyphenol–gelatin hydrogels with desirable properties and its potential applications. The results showed that the crosslinking effect of polyphenols with gelatin was affected by pH and the types and concentration of polyphenols. The network of polyphenol–gelatin on the microscopic level was ordered with 0.075% polyphenol (anthocyanin, tea polyphenol and procyanidin). The polyphenol–gelatin hydrogel exhibited the highest system stability and the best freeze‐dried network structure at pH 8. According to the results of circular dichroism (CD), ultraviolet (UV), and Fourier transform infrared spectroscopy (FTIR), both the solutions and freeze‐dried samples of polyphenol–gelatin under optimised conditions showed more ordered microstructure than pure gelatin. The addition of polyphenols posted significant impacts on changed the secondary structure of polyphenol–gelatin complexes. Also, the anthocyanin–gelatin hydrogel generally showed the higher encapsulation efficiency than pure gelatin and other polyphenol–gelatin samples, of which the highest mineral loading capacity (Mg, Mn and Cu) was 7.04% higher than that of pure gelatin, where anthocyanin acted as a crosslinker under alkaline condition that greatly improved the microstructure, stability and nutrition encapsulation efficiency of gelatin.