Degradation of olive oil by light or heating.Comparative electronic nose and sensory analysis data

MESSINA, V.; BABY, R.; CALVIÑO, A.; CABEZAS, M.; WALSOE DE RECA, N

Journal of Argentine Chemical Society

Asociacion Química Argentina

Lugar: Buenos Aires; Año: 2005 vol. 93 p. 57 - 67

The importance of sensory results is growing since legislation in various countries includes sensory essays to be performed for commodities previously to their commercialization. In case of olive oil, several descriptive norms have been already established. Standards, in European Communities legislation, by which the authenticity of virgin olive oil can be judged, should take into account not only its chemical composition but also its genuine sensory attributes. However, sensorial analysis suffers from some major drawbacks coming from the subjectivity of human judgement, which strongly depends on many physical and psychological factors. For this reasons, the electronic nose (EN) has been developed and improved in the last decades to be used as comparative tool. The advantages of EN in comparison with the human olfactory system include: higher objectivity, invariable response with time assuring the success of routine analysis. The aim of this work was to compare results of the SA and NE analysis of the odors of edible oils: soybean oil, sunflower oil, olive oil (before called ordinary olive oil) and virgin olive oil, and the different oxidation processes of olive oil and virgin olive oil under day light or heat effects. Edible oils suffer degradation by exposition to air, heat, light being this oxidation also influenced by antioxidants and by the fatty acid composition of oils .Volatile compounds appear in different oils because of lipolysis and oxidation processes. Lipolysis (enzymatic and microbiological activity) usually starts when oil is still in the fruit, while oxidation begins after the oil is obtained from the fruit and proceeds mainly during its storage. C6 and C5, especially C6 linear unsaturated and saturated aldehydes represent the most important fraction of volatile compounds, meanwhile C7-C11, monounsaturated adehydes or C6-C10 dienals, or C5 ramyfied aldehydes and alcohols reach, high concentrations in the aroma of virgin oliva oil affected by organoleptic defects.