Chickpea protein concentrates: extraction, structural characterization, and functional properties

Chickpea (Cicer arietinum) is an inexpensive pulse that is rich in proteins, vitamins, minerals, and phytochemicals. Various approaches are used to extract chickpea protein for food product development. The extraction method significantly affects functional properties of proteins and influences sensory characteristics plus consumer acceptability. However, current knowledge of chickpea protein extraction for food applications is limited. Therefore, aim of this work was to improve the physiochemical and functional properties of isolated chickpea proteins using isoelectric pH-precipitation (IP) and dilution extraction (DE). IP method used chickpea flour (10%, w/v) in 0.1 M NaOH. Mixture was precipitated at pH 4.5 followed by freeze-drying. DE method used chickpea flour (30%, w/v) in 0.3 M NaCl solution. The supernatant was mixed with distilled water (1:3) followed by centrifugation. The resultant precipitate from each method was dialyzed and freeze-dried to obtain a protein concentrate. Proximate analysis showed that the concentrate from DE had higher protein content (64.5 ± 0.21%) than IP concentrate (61.06 ± 0.03%). The IP concentrate had higher surface hydrophobicity (46.33) than the concentrate prepared from DE (42.41). However, DE concentrate showed comparatively higher water-holding capacity (9.94 ± 0.19) and oil-holding capacity (9.94 ± 0.08 g/g) when compared to IP (2.92 ± 0.12 and 5.37 ± 1.70 g/g respectively). The DE concentrate also had higher emulsion stability than IP concentrate at pH 3, 5, 7, and 9. Oil droplet sizes were similar at pH 9 for both protein concentrates, although significantly higher values were obtained for IP protein at pH 5. Foam stability was significantly higher for DE concentrate at pH 9.  DE concentrate was significantly more digestible (81.68 ± 0.13%) than IP concentrate (75.88 ± 0.12%). We conclude that DE could be recommended as a better method to obtain isolated proteins with superior structural and functional properties than the traditional IP method.