Interaction Between Water-Soluble Flaxseed Protein and Monascus Yellow Pigments and Its Effect on Stability of Pigments

Monascus yellow pigments are common natural food pigments with various physiological effects, but their poor water solubility and sensitivity to light, heat, and pH, which limit their wide application in food field. Water-soluble flaxseed protein (FPW) was used as a carrier to prepare the complex between FPW amd Monascus yellow pigments. The interaction hehavior between two types of Monascus yellow pigments (Monascin, MS and Ankaflavin, AK) and FPW was studied using combined spectral method. The dispersion and stability changes of pigments combined with FPW and Monascus pigments (Mps) which riched in Monascus yellow pigments in aqueous solution were investigated. Fluorescence spectroscopic analysis indicated that both MS and AK bound to FPW in the static quenching mode, and there was only one binding site. The binding constant of FPW-AK system was larger than that of FPW - MS system. The results of thermodynamic parameters demonstrated that the main forces maintaining FPW - MS system were hydrogen bond and van der Waals force, while those maintaining FPW- AK system were hydrogen bond and electrostatic attraction. Synchronous fluorescence spectrum and three-dimensional fluorescence spectrum showed that the addition of MS or AK changed the microenvironment of the amino acid residues of FPW, resulting in the conformational change of FPW. Analysis of UV-Vis and infrared spectroscopy further indicated that the secondary structure of FPW was changed after the addition of MS and AK. In addition, the combination of FPW and Mps could improve the dispersibility of Mps in water. After forming complexes with different concentrations of FPW, the retention rates of FPW-Mps were increased by 9. 53%, 16. 92%, and 31. 37% compared to free Mps at a temperature of 25 ℃, a light intensity of 3 900 Lux, and a light duration of 72 h. At temperatures of 4, 25, and 50 ℃, and under light avoidance conditions, the retention rates of FPW - Mps increased by 25. 65%, 22. 04%, and 25. 98% compared to free Mps. At a temperature of 25 ℃, pH values of 3, 5, 7, 9, and 11, and under light avoidance conditions, the retention rates of FPW - Mps increased by 10. 27%, 12. 96%, 12. 06%, 17. 82%, and 7. 27% compared to free Mps, respectively. After composite with FPW, the retention rates of Mps increased under different illumination time, temperatures, and pH conditions, indicating that FPW could improve the photostability, thermal stability, and acid-base stability of Mps. This study aimed to provide new ideas for the stability study of Monascus yellow pigments. © 2024 Cailiao Daobaoshe/ Materials Review. All rights reserved.