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The influence of rosemary on stability and bitterness of virgin olive oil

Spices and herbs have been used for long time to improve flavour and extend the shelf life of different foods. The spices from Lamiaceae family, especially rosemary (Rosmarinus officinalis L.), are well known for their antioxidative properties. Since rosemary as a spice is frequently combined with olive oil, in this study the influence of rosemary on stability and sensory properties of olive oil was investigated. Dry rosemary leaves (5% of integral or ground) as well as rosemary methanol extract (0, 02%) were added to virgin olive oil. Leaves were macerated in oil for 5 days in dark at ambient temperature with occasional shaking, and afterwards removed by filtration. In all oil samples, content of total polyphenols and o-diphenols, intensity of bitterness, oxidative stability by Rancimat test and sensory characteristics, were determined. Rosemary leaves and extract were effective antioxidants for olive oil. Addition of ground leaves had the greatest influence on extension of induction period. Oil samples with integral leaves and rosemary extract had similar oxidative stability. Maceration of ground leaves also increased the intensity of bitterness and the content of phenolic compounds of oil, causing the rosemary odour and bitterness very noticeable in sensory evaluation. However the addition of integral rosemary leaves and rosemary methanol extract did not significantly increase the content of phenols and oil bitterness.

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