Response surface methodology for investigating structure–function relationship of grain legume proteins

Abstract

Effect of physicochemical properties and secondary structure conformation, on the functional properties of protein concentrates prepared from grain legumes was investigated using response surface methodology. Appropriate models were built on the basis of the best subset technique. Oil‐holding capacity was mainly influenced by the secondary structure of proteins, particularly unordered structure, β‐sheet, and β‐turn. Protein solubility depended on secondary structure and surface hydrophobicity of proteins, and solubility decreased with increasing hydrophobicity. Interaction between solubility and hydrophobicity was significant for emulsifying activity, and EA increased with increasing solubility and hydrophobicity. High emulsion stability of legume proteins necessitated high β‐turn secondary structure proportion, solubility, and hydrophobicity. Protein unfolding, particularly high unordered, and β‐turn structures and high solubility were required for high foaming ability of legume proteins. In summary, the importance of this study was to increase the utilization of grain legume proteins in the food and non‐food industry. Practical applications It is important during food processing or when using an underutilized grain legume protein source as ingredient or supplement in the formulation of food products, to predict the functional properties of the protein. Functional properties are important for the consumer acceptance of food product. The physicochemical properties of protein such as surface hydrophobicity and secondary structure could be used as a basis to predict functionality. In this connection, this study provided effects of the variation of physicochemical properties and secondary structure of grain legume proteins on oil‐holding capacity, solubility, emulsifying and foaming properties. The aim of this study was to enhance the utilization of grain legume proteins as nutritional and functional ingredient.

Influence of pH and temperature on the physicochemical and functional properties of Bambara bean protein isolate

“…Protein solubility correlates to foam formation, emulsification, gelation and as such defines the usability of proteins in liquid foods and beverages ( Mune et al., 2017 ; Zayas, 1997 ). Effect of temperature on the solubility of the Bambara bean protein isolate at different pH is shown in Figure 3 b.…”

“…According to Mune et al. (2017) , emulsifying properties are essential in developing novel plant foods.…”

“…Aliquots of 500μl of the heat treated samples were mixed with 200μl of BPB (1 mg/ml) and vigorously stirred. The following steps of the procedure were described by Mune et al. (2017) and Mune Mune and Sogi (2016) .…”

“…The secondary structure of proteins in the heat-treated samples and the control was characterized by Fourier Transform Infrared (FTIR) spectroscopy ( Mune Mune and Sogi, 2016 ; Mune et al., 2017 ). Briefly, 0.05 mL of the samples was put between two aluminum foils.…”

“…FTIR spectra were obtained in the wavenumber range of 400–4000 cm −1 during 32 scans with 4 cm −1 resolution using a FTIR spectrometer (IRAffinity-1 Shimadzu, Japan). Data were analyzed as described by Mune et al. (2017) and the secondary structural features were calculated from the amide I envelope by non-linear regression fitting of Gaussian peaks of the original spectra.…”