Evaluation of canola seeds of different cultivars with special emphasis on the quantification of erucic acid and glucosinolates

Abstract

This study reports the characterization of the seeds and seed oils of five locally grown canola cultivars: Zafar-2002, Bulbul (Frontier), Dunkeld, Oscar and Con-11. The oil contents from canola seeds ranged from 34.3 to 39.3%. The levels of protein, fiber, ash and moisture were found to be 22.1-41.0, 12.0-14.0, 3.0-3.5 and 4.0-7.5%, respectively. The glucosinolate (GSL) contents in the canola seeds examined ranged from 49.7 to 78.1 mmol g^-1. The extracted canola seed oils revealed an iodine value of 118.2-124.6 g of I/100g of oil; refractive index (40 °C), 1.460-1.464; density (24 °C), 0.914-0.919 mg mL–1; saponification value, 187-195; unsaponifiable matter, 0.51-1.10%; acidity (% as oleic acid), 0.40-1.40, and color (1-in. cell), 1.35-1.73 R + 21.0-38.0 Y. Peroxide value (meq/ kg of oil) and specific extinctions at 232 and 270 nm were determined to be 2.00-7.08, 2.17-3.16 and 0.44-0.91, respectively. The seed oils of the five canola cultivars mainly consisted of oleic (C18:1), linoleic (C18:2) and linolenic (C18:3) acids at levels of 49.16-62.14, 14.61, 23.45 and 6.97-9.10%, respectively. The concentrations of palmitic (C16:0), stearic (C18:0), erucic (C22:1) and gadoleic (C20:1) acids ranged from 3.47 to 6.00, 1.51 to 2.10, traces to 13.03 and 1.30 to 10.63%, respectively. A small amount of arachidic acid (20:0) with a contribution below 1% was also detected. The contents of tocopherols (α, γ, and δ) in the canola oils accounted for 77.1-270.3, 191-500, 3.5-15.6 mg kg^-1, respectively.The presence of rather high levels of erucic acid and GSL in the present analysis of canola emphasized the need to further reduce the contents of these two antinutritional constituents in the investigated cultivars.