Physical and Chemical Properties of Density‐Graded Industrial Hemp Seeds, Extracted Oil, and Protein in Defatted Meal

ABSTRACT The indeterminate flowering nature of industrial hemp results in harvested seeds with varying maturity. This study employed density grading to separate seeds into fractions with different test weights, which were characterized for physical properties, chemical composition, and oil quality. Grading shifted 73.2% of seeds to heavier fractions with significantly greater thousand‐seed weight (14.6–17.8 g), bulk density (530–581 g/L), and true density (1129.5–1149.0 g/L) compared to lighter fractions (7.1–12.6 g; 334–500 g/L; 1089.2–1223.7 g/L, respectively). Heavier seeds were darker (L* 48.17–49.16 vs. 50.07–53.16) and contained more oil (29.2%–31.0% vs. 14.1%–23.3%). Protein (21.2%–25.3%) and ash (4.1%–4.6%) varied minimally, while crude fiber was highest in the lightest fraction (43.3%). Cold pressing recovered 56.7%–69.4% of oil; hexane extraction of the press cake achieved 99.8% overall recovery. Cold‐pressed oils were lighter (chlorophyll 14–37 ppm) than hexane‐extracted oils (75–85 ppm). Linoleic (52.6%–53.5%), α‐linolenic (16.2%–17.2%), and oleic acids (12.4%–13.6%) were predominant fatty acids. Palmitic acid was the major saturated fatty acid (8.2%–10.8%). Oils from heavier seeds contained more monounsaturated fatty acids, while polyunsaturated levels were similar across fractions. Protein solubility was higher in heavier seeds, dominated by glutelins (57.5%–65.7%), followed by globulins (9.1%–13.6%) and prolamins (8.0%–9.4%). Extended storage at 23°C and high polyunsaturated content caused severe oxidation, rendering oils unsuitable for food but suitable for biofuel, lubricants, or refining into fatty acids, mono‐ and diglycerides, and glycerol.