Conservation of refined oils

The objective was to assess the minimum durability date (MDD) of refined rapeseed and sunflower oils following criteria relevant to oxidative risk on samples stored in bulk (12 weeks) and then in bottles (18 months), in summer and winter periods.

The oxidation induced by bulk storage and its dependence on the storage temperature is directly linked to the nature (proportion of polyunsaturated fatty acids in particular) and the initial quality of the oils concerned: significant for sunflower oil, which already showed a significant degree of oxidation on receipt, it appeared more moderate for rapeseed oil.
The oxidation levels reached during the study had no significant impact on the anisidine index, the tocopherol content and the proportion of polar compounds (oxidised triglycerides in particular).

The two types of oil showed an increasing intensity of colouring, linked to their ageing, and tending towards a stabilised maximum value, whatever the storage conditions.

The relevance of using the peroxide value as an early marker of organoleptic degradation due to oil oxidation was confirmed (recommended threshold of 10 meqO2/kg at DDM).

Finally, although sensory analysis is directly correlated with the objective of organoleptic neutrality sought by the consumer, it did not prove sensitive enough to characterise the oxidative evolution at the levels reached during the study.

Contact: Loïc Leitner, Head of Analytical Research, ITERG.