Development of Zein/tannic acid nanoparticles as antioxidants for oxidation inhibition of blackberry seed oil emulsions

The zein-tannic acid nanoparticles (ZTNPs) were developed as antioxidants for oxidation inhibition of blackberry seed oils. These particles were spherical with an average diameter below 200 nm. The results of structural characterization indicated that tannic acid was bound to zein by electrostatic, hydrophobic, and hydrogen bonding interactions, resulting in the conformational changes of zein. The antioxidant capacity of zein was significantly improved by binding of tannic acid, which suggested ZTNPs had a 2-Phenyl-4,4,5,5-tetramethylimidazoline-1-oxyl 3-Oxide (PTIO) radical scavenging rate as high as 77.5 % at pH 4. Moreover, ZTNPs at pH 7 exhibited a higher thermal stability and better resistance to emulsion lipid oxidation. They inhibited the formation of ROOH and TBARS of blackberry seed oil emulsions during storage by covering at the oil-water interface with an adsorption rate of approximately 100 %, forming a dense particle film to reduce the oxygen content and prevent the continuation of the oxidation process.