Effect of pressing and combination of three storage temperatures and times on chemical composition and fatty acid profile of canola expellers

Abstract

This experiment investigated the effects of combinations of three temperatures and storage times on chemical composition, fatty acid profile, and oxidative stability of canola expellers obtained from the cold-pressing extraction of oil. Canola seeds were single-crushed at moderate temperatures (60°C) during 3 pressing sessions. Nine samples (100±1 g) of each session were collected, inserted into sealed bags, stored at three temperatures (12, 24, 36°C) over 3 periods of time (10, 20, 30 d). Then, samples (100±1 g) of canola seeds collected before each pressing session and canola expellers collected before and after each storage time were analyzed for chemical composition, fatty acid profile, peroxide number and Kreis test. Before storage, the fatty acid profile of canola seeds and expellers differed significantly, except for myristic (P=0.18), palmitic (P=0.57), oleic (P=0.07), and α-linolenic acids (P=0.45). Compared to canola seeds, expellers showed greater content of saturated, poly-unsaturated, and n-6 fatty acids (P<0.01), but a lower content of mono-unsaturated fatty acids (P<0.01). Peroxide values were definitely (P<0.01) greater for expellers and averaged 4.22 and 4.11 mEq/kg fat before and after storage, respectively. The Kreis test was negative for all samples. Under different temperatures and times of storage, canola expellers showed to maintain a good oxidative stability, as highlighted by low peroxide values (<10 mEq/kg fat) and negative response for Kreis test. Canola expellers obtained by on-farm cold extraction, despite great oil residual (from 17 to 19% ether extracts on dry matter basis), can be stored at farm without significant chemical and nutritional changes.

Keywords

• Canola expellers, Oil extraction, Fatty acid profile, Oxidation, Bio-fuel.