Physicochemical characteristics of density-graded industrial hemp grain

Authors: Evangelista, Roque; Hojilla-Evangelista, Milagros - Mila; Cermak, Steven - Steve

Submitted to: Association for the Advancement of Industrial Crops Conference
Publication Type: Abstract Only
Publication Acceptance Date: 8/27/2023
Publication Date: 8/27/2023
Citation: Evangelista, R.L., Hojilla-Evangelista, M.P., Cermak, S.C. 2023. Physicochemical characteristics of density-graded industrial hemp grain [abstract]. Association for the Advancement of Industrial Crops Conference. p.88.

Interpretive Summary:

Technical Abstract: Industrial hemp grain is harvested when shattering begins, which typically happens when 70-85% of the grains are mature. The grains harvested, therefore, contain a substantial proportion of immature seeds. To assess the quality of the harvested hemp grain, dried grain (cv Henola) was density-graded into six fractions. Bulk and true densities, thousand seed weights (TSW), and proximate composition (moisture, oil, protein, and ash contents) were determined for each fraction. Oils obtained from each fraction by cold-pressing followed by hexane extraction were analyzed for acid value, color (CIE L*a*b* color scale), and chlorophyll content. The defatted meal was analyzed for the soluble protein classes (water-soluble albumin, saline-soluble globulin, ethanol-soluble prolamin, and alkali-soluble glutelin). Seventy three percent of the fraction had densities and TSW greater than the starting bulk grain (538 g/L). The starting bulk grain had 28.6% d.b. oil while the density-graded fractions ranged from 31% (heaviest fraction-46%) to 14% (lightest fraction-7%). Significant difference in crude protein content was observed only between the heaviest and the lightest fraction at 25.3% and 21.2%, respectively. Cold-pressed oil had markedly lower acid values than hexane-extracted oils and were also significantly lighter (>70 L* versus <13 L*, scale ranges from 0 - black to 100 - white). The difference in color was consistent with the amount of chlorophyll extracted with the oil. Glutelins were the major soluble protein group in defatted hemp grain meal, accounting for 58.6% of total protein in the heavy fraction and 41.2% in the light fraction. The two fractions had close amounts of albumins and globulins (7-9% and 11-13%, respectively). Prolamin content was the least; its amount in the light fraction (6%) was double that in the heavy fraction. Density-grading can be utilized to separate the light (immature) grains to keep the oil’s acid value and color low, thus reducing the cost of oil refining and bleaching. The light grains can still be processed for other applications where quality is not critical.