The antioxidative activity of summer savory (Satureja hortemis L.) and rosemary (Rosmarinus officinalis L.) in dressing stored exposed to light or in darkness

For an oil-in-water emulsion dressing, addition of 0.15% of dried leaves of summer savory (Satureja hortensis L.) or more significantly of rosemary (Rosmarinus officinalis L.), resulted in a significantly better antioxidative protection than addition of 80 ppm propyl gallate (standard concentration for this type of product) during dark storage at 19 °C for up to 24 weeks, as determined by development of conjugated dienes, peroxide value, head space hexanal and thiobarbituric acid-reactive substances. Addition of freeze-dried methanol extract of the two spices, in an equivalent concentration, had less antioxidative effect, but was comparable to the effect of propyl gallate. Exposure to fluorescent light (850 lux) during storage had a clear pro-oxidative effect for dressing with or without spice or spice extract added, when compared to dark storage. For dressing with extract of savory added, the antioxidative effect found for dark storage was during light exposure, changed to a pro-oxidative effect, and a hexanal level as high as 600 mg kg−1 oil was detected after 8 weeks of storage, while the net antioxidative effect of rosemary was maintained for storage exposed to light.