Millet bran globulin hydrolysate derived tetrapeptide-ferrous chelate: Preparation, structural characterization, security prediction in silico, and stability against different food processing conditions

Through Sephadex gel chromatography, reverse-phase-high-performance-liquid-chromatography and ultra-high performance-liquid-chromatography coupled with electrospray ionization mass spectrometry analysis, a novel tetrapeptide (Ser-Glu-Leu-Glu) of excellent ferrous-chelating capacity (41.24 μmol/g) was identified in millet bran globulin hydrolysate. Physicochemical properties and security of SELE were predicted in silico. The result showed that SELE was no toxic. Based on a model generated from response surface methodology, the optimum preparation conditions of SELE-ferrous chelate were obtained with the mass ratio of SELE to FeCl2·4H2O of 43.3: 1, at pH 6.7 and 28.7 °C for 28.8 min. The ferrous-chelating ratio of SELE was 97.06% under these conditions. Structure of SELE-ferrous chelate was characterized with ultraviolet spectroscopy, Fourier-infrared spectroscopy and scanning electron microscope. The results demonstrated that amino group and carboxyl group of SELE were the primary ferrous-chelating sites. Moreover, SELE-ferrous chelate showed higher iron-solubility than FeCl2 and ferrous lactate against different pasteurization conditions, heating at 100 °C for 30 min, and various pH values (P < 0.05). SELE-ferrous chelate also demonstrated higher iron-solubility than FeCl2 and ferrous lactate against simulated gastrointestinal digestion (P < 0.05). These results indicated that SELE could be used as ingredient of iron fortifications and had potential applications in the food industry.