Production of protein concentrate from clear flour as a semolina industry by-product and investigation of some functional properties

In this study, two different protein concentrates were produced using different extraction solvents from each of defatted clear flours (dCF-1 and dCF-2). Protein contents of dCF-1 and dCF-2 were %14.2 and %17.7 on dry weight basis, respectively. Protein concentrates produced from dCF-1 using distilled water and 0.15 M NaCI were defined as PC-1S and PC-1T, respectively, and protein concentrates produced from dCF-2 were called as PC-2S and PC-2T, respectively. Functional properties of protein concentrates, such as protein solubility, emulsion capacity and stability, foaming capacity and stability, were investigated at 1% concentration in distilled water as a function of pH of the medium. Water holding and oil absorption capacities of protein concentrates were also studied. Some protein concentrates were used as an egg replacer at certain concentrations in muffin cake formulations in order to compare some quality properties with control cake. Protein contents of PC-1S, PC-2S, PC-1T and PC-2T were 93.4%, 88.7%, 90.8% and 91.0% on dry weight basis, respectively. Water holding capacities (g H2O/g) of PC-1S and PC-2S extracted using distilled water were higher than that of the PC-1T and PC-2T extracted using salt water. The highest protein solubility value was determined with the protein concentrates of PC-1S at pH 2 (81.9%). The highest emulsion capacity and stability values were detected with the protein concentrate of PC-1S at pH 8 (61.8%) and pH 2 (64.2%), respectively. The highest foam volume (cm3) and foam half-life (s) values were determined with the PC-2S at pH 8 (115.8 cm3) and with the PC-1S at pH 2 (116.3 s), respectively. Protein solubility, emulsifying and foaming properties of protein concentrates were the lowest at pH 6. The muffin cake prepared with 3% (w/w) PC-2S protein concentrate instead of half of the whole egg as an egg replacer was similar to control cake in terms of physical properties. The muffin cake produced with only 3% PC-1S instead of the whole egg was comparable to control cake in terms of textural properties. The control muffin cake had the highest point due to sensory properties of color and brightness/appearance, whereas the muffin cake produced with 1.5% PC-2S instead of half of the whole egg as an egg replacer had the highest points in terms of other sensory properties and general acceptability.