EFFECT OF HEAT-TREATMENTS ON CANOLA PRESS OILS .2. OXIDATIVE STABILITY

Oxidative stability of the canola press oils increased with increasing heat treatment to the seed, and decreased on refining. The tocopherol content of the press oils was relatively uniform and could not account for the observed variations in oxidative stability. The variation in stability corresponded to variations in the content of other non-triglyceride components. In general, the greater the initial quality of the oils, i.e., the lower the content of non-triglyceride material, the lower their oxidative stability. Oxidative stability was found to be significantly correlated to phosphorus content (R2 > 0.99). This could be explained by synergism between tocopherols and phospholipids, in the range from 0.025% to 0.22% phospholipid. Above this level increasing the phosholipid content did not significantly improve the oxidative stability. After oxidation the oils were "bleached", i.e., there was a loss of color bodies. This loss was related to both the original content of color bodies in the oil and the degree of oxidation of the oil.