Effects of the dark blue pigment from Vaccinium bracteatum Thunb leaves on the physicochemical properties of rice protein

Abstract

Objective: This study was to explore the improvement of structural and emulsifying properties of rice protein by interacted with the dark blue pigment of Vaccinium bracteatum Thunb leaves. Methods: The dark blue pigment was prepared from VBTL, and the changes of structural and emulsifying properties of rice protein before and after dyeing were analyzed. Results: The formation of binary complexes between the dark blue pigment and the rice protein decreased the color values of L* and b*, and the hue of the pigment-protein complex changed to dark blue color with the increase of the pigment concentration. The water solubility of the pigment-protein complex increased, and the oil-holding capacity decreased significantly. The analysis circular dichroism spectroscopy showed the changes in the secondary structure of pigment-protein complex with a decreasing in the relative content of α-helices and β-folds and an increasing in the relative content of β-turns and random coil. At the concentration of pigment below 1.5%, foam stability increased, while foaming capacity, emulsifying capacity and emulsion stability decreased. When the concentration of pigment was higher than 1.5%, foam stability decreased, while foaming capacity, emulsifying capacity and emulsion stability increased. Conclusion: The dark blue pigment can improve the emulsifying properties of rice protein by changing its secondary structure.

Keywords

• vaccinium bracteatum thunb leaves
• dark blue pigment
• rice protein
• secondary structure
• emulsifying property