The occurrence of hydrogen peroxide in edible oils; chemical and microbiological consequences

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AbstractEvidence is presented for the occurrence of hydrogen peroxide at low concentration in edible oils and fats of both vegetable and animal origin.In soya bean, corn, groundnut, sunflower, rapeseed, olive, safflower, sesame, linseed and mackerel oils, and in the oil from lard, margarine and a solid vegetable fat, hydrogen peroxide was found at concentrations within the range 0.1‐11.5 μg g−1 of oil. The highest ‘natural’ concentrations were found in soya bean oil. Detection of hydrogen peroxide in aqueous extracts of the various oils examined was based upon measurements by high performance liquid chromatography, luminescence, colorimetry and fluorimetry. The quantitative measurement of hydrogen peroxide was made using a fluorimetric assay.The hydrogen peroxide concentration found in a given oil was not directly related to the peroxide value of that oil. Hydrogen peroxide was found to re‐accumulate in oil samples which had been washed free of their initial content. This process took place slowly over a period of days, and led to a steady state concentration of hydrogen peroxide in the oil. It is suggested that hydrogen peroxide arises as a by‐product of the lipid autoxidation process.The rate of oxidation and the induction period at 40°C of soya bean oil ‘naturally’ containing 2.76 μg hydrogen peroxide per gram of oil were unaffected by the removal of hydrogen peroxide by water washing or by addition of further hydrogen peroxide to the oil. The hydrogen peroxide did not therefore appear to function as a significant source of hydroxyl radicals capable of initiating autoxidation reactions.In the presence of soya bean oil containing hydrogen peroxide (5 μg g−1) the lethal effect of heating at 90°C on spores of Clostridium sporogenes PA 3679 was much greater than that in a liquid paraffin control. Removal of hydrogen peroxide from the soya bean oil by washing with water considerably reduced the lethal effect, which was restored by the addition of hydrogen peroxide (7.5 μg g−1) to the washed oil.