Experimental and modeling approaches applied to the whey proteins and vitamin B9 complexes study

Abstract

In this work, complexes of β-lactoglobulin (βlg) or whey protein isolate (WPI) with folic acid (FA) were developed as potential food ingredients. A dilute concentrations regime was employed to elucidate possible binding sites of the vitamin on the protein. The ζ potential, the aggregation kinetics and the particle size distributions were studied. On the other hand, in silico studies were carried. Additionally, the ability of the mixed systems to preserve the vitamin bioaccessibility was assessed by exposing the protein-FA systems to in vitro digestion. The ζ potential study showed similar values for the pure proteins and the mixed systems, obtaining for the highest concentrations studied (0.01825% W/W) values of: 21 ± 1 and 29 ± 2 mV for βlg and βlg-FA, and 22 ± 1 and 23 ± 2 mV for WPI and WPI-FA. These results suggest that the interactions between FA and proteins are of the hydrophobic type. The aggregation kinetics showed that the process of formation of protein-FA was slower than the formation of pure FA crystals. The particle size distributions showed different sizes between the pure proteins and those of the mixed systems. Regarding in silico studies, it was found that βlg presents regions where hydrogen bonding interactions between FA and certain amino acids of the protein prevail. Finally, regarding the bioaccessibility of the vitamin, WPI-FA was the system that obtained the highest value (92%). These complexes could be used as ingredients to be incorporated into foods consumed by people with special diets such as pregnant women.