Effects of Ferulic Acid on the Aggregation Behavior of Gluten Protein Components

The growing consumer demand for whole grain foods, which are rich in minerals, vitamins, and phenolic acids, has highlighted the importance of understanding the role of these bioactive compounds in modulating the functional properties of wheat-based products. Ferulic acid (FA), a predominant phenolic acid in whole grains, has been shown to play a critical role in the polymerization of gluten proteins, which are the key determinants of dough viscoelastic properties and end-product quality.

Recent studies have revealed that FA can form covalent cross-links with tyrosine residues, thereby influencing dough rheology. Additionally, FA's interactions with cysteine residues can impact gluten protein aggregation and the formation of the gluten network structure. This helps mitigate the adverse effects of water-unextractable solids from bran, which can otherwise compromise the development of a stable gluten network.

However, the specific mechanisms by which FA affects the aggregation behavior of the critical gluten protein components, namely gliadin and glutenin, remain elusive. This study aims to elucidate the influence of different FA concentrations on the free sulfhydryl content, molecular weight distribution, and particle size distribution of these gluten protein fractions. The surface morphology of the protein samples was also characterized using atomic force microscopy (AFM) to provide insights into the multi-scale structural changes induced by FA.

Materials and Methods

The study was conducted at the Food Science and Engineering College of Nanjing University of Finance and Economics. Gliadin, glutenin, and total gluten protein samples were prepared and treated with varying concentrations of FA (0%, 0.5%, and 1.0%). The free sulfhydryl content, molecular weight distribution, and particle size distribution of the protein samples were analyzed using established methods.

Results and Discussion

The results showed that the addition of 0.5% FA reduced the free sulfhydryl content of glutenin and total gluten protein, while increasing the average particle size of the gluten protein. SDS-PAGE analysis and AFM imaging revealed that the 0.5% FA treatment promoted the aggregation and cross-linking of the lower molecular weight protein components, leading to the formation of larger protein assemblies.

In contrast, higher FA concentrations (1.0%) significantly reduced the tyrosine doublet peak ratio in glutenin and increased the polarity of the tryptophan microenvironment, which favored the formation of disordered protein structures. This, in turn, hindered the development of a stable gluten network structure.

This study provides valuable insights into the mechanism by which FA modulates the aggregation behavior of gluten protein components. The optimal FA concentration of 0.5% was found to enhance the cross-linking and aggregation of the lower molecular weight proteins, leading to the formation of a more uniform and stable gluten network structure. These findings can inform the development of whole grain wheat-based products with improved textural and quality characteristics.