Chemical analysis
Moisture, ash and total protein content of whole seed and meal were analysed according to AOAC Official Method 934.01, AOAC Method 942.05 and AOAC Method 990.03 with combustion-based nitrogen content using 6.25 as a conversion factor (Latimer & Horwitz, 2005), respectively. The level of phytate was determined using the method described by Oomah et al. (2008) with modifications. 2% (v/v) HCl and centrifugation at 1000 × g for 20 min were used to obtain the extract containing phytate. The anion exchange column (AG-1-X8, Bio-k Laboratories Inc.) was equilibrated with 0.08% (v/v) HCl before addition of extract and the eluate (150 μL) was mixed with Wade reagent (50 μL; FeCl3∙6H2O + sulfosalicylic acid) in a microplate well. The extraction of phenolic compounds was carried out using 70% aqueous acetone (1:30, w:v, meal-to-solvent ratio) at room temperature for 1 h. The extract was then centrifuged at 10,000 ×g for 20 min and the absorbance of the recovered supernatant was measured at 326 nm (Bio-Rad xMarkTM microplate spectrophotometer, Bio-Rad Laboratories Inc.). Total phenolic content was expressed as sinapic acid equivalent/g of meal as per Oomah et al. (2010). Meal amino acid content (18 amino acids, asparagine and glutamine combined with aspartic and glutamic acid, respectively) was evaluated using AOAC Method 994.12 (Latimer & Horwitz, 2005).