Protein solubility of the seeds coat was determined as described by Aluko and Yada (1995) with little modification. Briefly, at pH 3.0–10.0 values, 1 mg of sample was dispersed in 1 mL of 0.1 M phosphate buffer solutions to obtain a 0.1% (w/v) concentration and the resulting mixture was vortexed for 2 min and centrifuged at 5000 rpm for 20 min. Protein content of the supernatant was determined using the method of Lowry, Rosembroug, Lewis, and Randall (1951). Total protein content was determined by dissolving coat flour in 0.1 M NaOH solution. Protein solubility was expressed as percentage ratio of supernatant protein content to the total protein content.