The effect of bioactive constituents on plant oil stability

Abuzaytoun, Reem (2005) The effect of bioactive constituents on plant oil stability. Masters thesis, Memorial University of Newfoundland.

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Abstract

Algal oils and oils rich in alpha-linolenic acid (ALA), and gamma-linolenic acid (GLA) have been used for the treatment of a wide range of nutritional and clinical disorders. The algal oils of interest were arachidonic acid single cell oil (ARASCO), docosahexaenoic acid single cell oil (DRASCO), and a single cell oil rich in docosahexaenoic acid (DHA) and docosapentaenoic acid (n-6 DPA) (OMEGA-GOLD oil). Flax oil contains ALA, and hemp oil is rich in both ALA and GLA. Little information is available about the oxidative stability of these nutritional oils and their bioactive minor constituents. Therefore, this research was initiated to evaluate the oxidative stability of flax, hemp, ARASCO, DRASCO, and OMEGA-GOLD oil, as well as their minor component-stripped counterparts, in the dark at 60°C and under fluorescent light at 2rc. Several analytical methods were used to assess the oxidative stability of these oils. Oil extracts were also investigated for their radical scavenging activity towards the stable 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical by a spectrophotometric method and measuring their total phenolic contents. -- The results indicate that bioactive constituents of these nutritional oils play a major role in their oxidative stability in the dark as well as in the light. However, the fatty acid composition of the oil and the total tocopherols as well as the type of pigments present contribute to their stability. It was found that non-stripped flax and hemp were more stable than their corresponding stripped counterparts. However, non-stripped hemp oil had a higher oxidative stability than non-stripped flax oil as indicated in radical scavenging activity towards DPPH radical and total phenolic contents. On the other hand, DHASCO contains a significant level of natural radical scavengers and phenolic compounds that contribute to its higher stability compared to ARASCO and the OMEGA-GOLD oil. The results demonstrate the importance of minor oil components on their oxidative stability, which will reflect on their food and supplement value as well as shelf life.

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