Nutritional composition and functional properties of Scottish cold-pressed hemp oil and by-products for sustainable food applications

Abstract

The expanding interest in sustainable oilseed systems has highlighted hemp (Cannabis sativa L.) as a source of nutritionally dense and multifunctional food ingredients. This study presents a comprehensive compositional and techno-functional characterisation of Scottish cold-pressed hemp seed oil and its industrial by-products (press cake and filtration-derived fudge) produced at commercial scale for the first time. Fatty acid profiling of the oils showed low saturated fatty acids (8.65%–8.93%), moderate monounsaturated fatty acids (8.55%–9.57%), and high polyunsaturated fatty acids (74.93%–76.92%), with ω-6 and ω-3 contents of 53.8%–55.3% and 19.4%–20.5%, respectively, yielding ω-6-to-ω-3 ratios of 2.67–2.82. Press cake and fudge contained 12.5%–22.5% and 38.3%–43.5% fat, 24.6%–32.7% and 29.0%–30.9% protein, and 4.97%–6.16% and 5.97%–15.14% ash, respectively. Total non-starch polysaccharides reached 19.8%–22.9% in cake and 2.85%–3.53% in fudge. Mineral concentrations were high, particularly in fudge, which contained 735–841 mg/100 g magnesium, 1.82–2.02 g/100 g phosphorus, 1.30–1.41 g/100 g potassium, 23.0–48.9 mg/100 g iron, and up to 11.82 mg/100 g zinc; cake contained 562–634 mg/100 g magnesium, 1.32–1.56 g/100 g phosphorus, and 17.1–24.8 mg/100 g iron. Essential amino acids in cake were present at nutritionally relevant levels, including leucine (2.37–3.08 g/100 g), phenylalanine (1.87–2.48 g/100 g), valine (1.83–2.37 g/100 g), and lysine (1.18–1.46 g/100 g). LC–MS/MS quantification of 175 phytochemicals showed markedly higher total levels in cake (up to 39.31 mg/100 g) than in fudge (up to 13.15 mg/100 g), with bound phenolics predominating; major constituents included siringaresinol, ferulic acid, and canabisin A. Cannabinoid analysis identified CBDA at 137.7–302.9 mg/100 g and CBD at 20.3–75.2 mg/100 g in oils, with lower concentrations in cake (CBDA 22.17–93.77 mg/100 g; CBD 3.58–25.30 mg/100 g) and higher levels in fudge (CBDA 117.4–297.3 mg/100 g; CBD 17.8–55.3 mg/100 g). Press cake demonstrated high oil-holding capacity (14.7–15.0 g/g), rapid wettability (∼100%), and moderate bulk density (0.45–0.47 g/cm³). These results provide an integrated compositional and functional dataset defining the nutritional, phytochemical, and techno-functional properties of Scottish hemp oil and its co-products, supporting their applicability as ingredients within grain-, oilseed-, and fibre-based food systems.