30A-28 |
Oxidation of olive oil exposed to still air |
A. KANAVOURAS1, A. Cert2, R. Mateos2, and R. J. Hernandez1. (1) School of Packaging, Michigan State University, East Lansing, MI 48824, (2) Instituto de las Grasas y sus Derivados, Seville, Spain Oxidation of edible oils under active mixing of air and oil leads to the production of peroxides compounds, which in turn react chemically to produces dimeric by products. However, no oxygen/oil mixing oxidation resulted in the formation of different by-products, accumulated over time. The non-mixing process is more representative of actual oxidation processes that take place during storage of oil. By studying oxidation at non-mixing conditions one can determine the actual quality characteristics of edible oils. In this work we study the static (non-mixing) oxidation of a purified olive oil at different air-exposed area to oil mass. Different amounts, 1.26, 2.5, 3.5 and 7g, of purified Tunis olive oil was placed in 12 mL, 2 cm ID, glass vials. The vials containing the oil were exposed to still air at 37°C under dark up to 60 days. This gave different exposed area/ oil mass ratio and therefore different length for the diffusing oxygen through the oil. The amount of oxidation by-products was a function of time an area/mass ratio. For the 7g vials oil analyzes were done for the top, middle and bottom fractions. Oxidation was analyzed by gas and liquid chromatography. Peroxide Index (PI), K232 and K270 extinction coefficients, total content and distribution of polar compounds, free fatty acids, and composition of triglycerides were evaluated. Results indicated that there were substantial differences in the speed of oxidation as a function of the amount of oil used. Less oxidative by-products per gram of oil were observed for smaller area/oil mass ratio. Analysis of the different fractions of the 7 g vials showed that the oxidation proceeded in a similar pattern in all of three fractions, indicating that the oxidation process is not oxygen-diffusion controlled.
Session 30A, Food Chemistry: Lipids
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