Functional protein from cumin seed (Cuminum cyminum): Optimization and characterization studies

Cumin seed protein isolate (CSPI) was found to be a potential source of bioactive protein. Box-Behnken Design was used in order to optimize the protein extraction parameters: extraction time (X1: 0.5–1.5 h), extraction temperature (X2: 20–40 °C) and buffer-to-sample ratio (X3: 10–30 mL/g). Extraction conditions for maximum protein yield were corresponding to X1 = 0.6 h, X2 = 26.3 °C and X3 = 10 mL/g. A close agreement between experimental (44.98 mg/g) and predicted (45.19 mg/g) values was found. The physicochemical properties (i.e. amino acid composition, protein components, protein structure) and its potential bioactivities (i.e. antioxidant and antidiabetic activity) were also evaluated, giving a better understanding of general structure and properties of CSPI. 2S albumin, 7S globulin, 11S globulin and lectin were found as the components of the extracted seed protein. Structure of CSPI was a mixture of intramolecular β-sheet (1639 cm−1), random coil (1642 cm−1), α-helix (1655 cm−1), β-turns (1660 cm−1) and antiparallel β-sheet aggregates (1690 cm−1) as shown in the FTIR spectra. CSPI was predominant with the Tyr, Glu, Asp, Arg, Leu and Phe, which could be considered as a high quality of natural protein. In addition, CSPI showed appreciable DPPH free radical scavenging activity (47.7 %DPPHsc/μg) and reducing power (12.4 mM/μg), which implied that CSPI could be used as a natural antioxidant agent. However, CSPI showed a relatively low α-amylase inhibition activity (6.7%). These findings demonstrated that CSPI could be a used as a potential nutraceutical or ingredient of functional and health-promoting foods.