An analytical toolbox of the relationship between molecular characteristics and functional properties of pea protein ingredients

Commercial pea protein ingredients have garnered increased attention in the development of food foams and emulsions. It is well known that the foaming and emulsifying properties of PP are somehow dependent on their molecular characteristics. However, the exact relationships between them are not fully understood. Hence, this project aimed to provide a comprehensive assessment of molecular characteristics and foaming and emulsifying properties for commercial PP ingredients. After this, their relationships would be explored by developing an analytical toolbox.
First of all, this project summarized various methods currently available for determining protein molecular characteristics and functional properties in Paper I. In chapter 3 (Paper II), the structural characteristics of PP ingredients were assessed using SDS-PAGE, FTIR, fluorescence and UV-vis spectroscopy and SXAS technique. The determination of physicochemical properties included particle size, zeta potential, surface hydrophobicity, solubility as well as surface/interfacial tension and rheology. In chapter 4 (Paper II&III), the foaming capacity and stability of PP ingredients were measured. Next, the emulsifying capacity was characterized by oil droplet size and distribution and CLSM. The zeta potential and viscosity were measured to provide information regarding emulsifying stability. The FI and CI were calculated to evaluate emulsion storage stability. At last, the accelerated stability was determined by LUMiSizer. In chapter 5, a dataset was generated after data compression. Pearson’s correlation, PCA and PLS statistical tools were used to analyze the relationships between molecular characteristics and foaming and emulsifying properties.
In conclusion, the conformational variations in primary, secondary, and tertiary structure gave rise to disparities in physicochemical properties, thereby leading to diverse foaming and emulsifying performances among seven PP ingredients. The correlation and PCA analysis revealed that the foaming and emulsifying properties were predominantly influenced by different variables. The prediction of FC and FS did not work well by PLS analysis, despite their high correlation with protein structural information. On the contrary, a good prediction was provided for instability index (emulsifying stability) using zeta potential of protein suspension, surface hydrophobicity, solubility, and ingredient proximity. Overall, such an analytical toolbox could give an overall picture of the relationship between molecular characteristics and functional properties for commercial PP ingredients. Besides, a rapid prediction on the emulsion stability of PP ingredients could be provided. This knowledge would be beneficial to modulate processing for the development of desired PP ingredients and facilitate their accurate application in diverse food products.