The oxidative stability of flavoured virgin olive oil: the effect of the water activity of rosemary

Abstract

Flavoured olive oil gained has importance in terms of its sensorial properties and oxidative stability in recent years. However, the water activity level of the flavouring agent can be important for oxidative stability. Therefore, the aim of this study was to determine the effect of the water activity of rosemary, which was used as a flavouring agent, on the oxidative stability of olive oil. For this purpose, rosemary samples were adjusted to different levels of water activity (0.17, 0.24 and 0.44) and used for the aromatization of virgin olive oils. At the end of the aromatization, the olive oil samples were exposed to an accelerated oxidation test at 60 °C for 28 days. The peroxide, p-anisidine, TOTOX (total oxidation index), free fatty acid, chlorophyll, carotenoid and specific extinction values of the samples were determined. According to the results, the oxidation of olive oils is limited by decreased water activity values in the rosemary samples. Moreover, unflavoured oils were identified as being more sensitive to oxidation when compared to flavoured oils. Additionally, storage time had important effect on all of the analysed parameters. The present research showed that the water activity of rosemary, when used as condiment, affected the oxidative stability and carotenoid content of virgin olive oil. Using rosemary with a low water activity value to flavour olive oil was more effective in terms of oxidative stability. These findings implied that the oxidation of flavoured olive oil could be decreased by decreasing the water content of the condiment used.