S OYBEAN oil is a common vegetable oil, which is used for edible purposes. However, this oil is rich in unsaturated fatty acids that enhance oil deterioration by their oxidation. Such deterioration can be reduced using suitable antioxidants, preferably natural antioxidants. This work was made to assess the suitability of phenolic compounds that can be extracted from olive leaves to improve soybean oil stability against oxidation. Olive leaves extracts were tested for their content of phenolic compounds and have been then added to soybean oil which was subjected to accelerated oxidation. The oxidation stability was monitored following several technical methods commonly used for this purposes such as peroxide value, p-Anisidine value, as well as induction time by Rancimat method. The results have proved that the extracts of olive leaves can be used efficiently as a safe natural antioxidant in edible oils. However, the dose to be added should be adjusted as to achieve the activity of synthetic antioxidants.

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Saffron consists of bioactive compounds with health-promoting properties and is mainly used in medicine, flavoring and coloring. In this study, we aimed to investigate the effect of extraction methods on the antioxidant activity of saffron (Crocus sativus L.) extracts (SE) and to evaluate the antioxidant performance of SE in vegetable oils. Saffron stigmas were extracted in water, ethanol, methanol, and their combinations using maceration extraction (ME), ultrasonic-assisted extraction (UAE), microwave-assisted extraction (MAE), and the combination of UAE with MAE. The results showed that the sample extracted by methanol/water (50:50) using the combination of UAE with MAE methods had the highest amount of total phenolic content (31.56 mg/g GAE) and antioxidant activity (83.24% inhibition). The extract with the highest antioxidant activity was freeze-dried before incorporation into oil samples. Freeze-dried SE contained trans-crocin-4 and trans-crocin-3 (most abundant constituents), kaempferol, and picrocrocin. Moreover, the addition of SE at 1000 ppm resulted in a significant increase in the oxidative stability of canola (CAO), sunflower (SO), and corn oil (COO).