Enriching kernel fraction by milling
The seeds (300 g/ batch) were milled using a 6-inch wide x 6-inch diameter (15.24 cm x 15.24 cm) roller mill with 24 corrugations per inch (9.4 corrugations/cm). The slow and the fast rollers have fixed speeds of 358 and 804 rpm, respectively. Initially, the gap of the rollers was set at 0.02 inch (0.51 mm). The milled seeds were then sifted through a stack of 5-, 12-, 18-, and 25-mesh (4.0, 1.7, 1.0, and 0.7 mm) screens. The fractions on 5- and 12-mesh screens (+5M and +12M) were roller-milled again (with the roller gap reduced after each pass) to recover more kernels still attached to the hulls and screened again. The fractions retained on 18- and 25-mesh screen (+18M and +25M) were aspirated to remove the light material, while the heavier fractions were milled again to pass through the 25-mesh screen. The -25M fractions were combined and defatted with hexane using a Soxhlet extractor. The defatted enriched kernel meal was air-dried in the hood overnight and stored in a capped glass jar under ambient conditions until used.