The antioxidant activity of relatively polar extracts from virgin olive oil was investigated in sunflower oil stripped of tocopherols and in tocopherol-stripped sunflower oil-in-water emulsions. The extracts were found to be effective as antioxidants in both media in the absence of added metal ions. However, the antioxidant activity was markedly reduced by the presence of added ferric chloride. In sunflower oil-in-water emulsions (pH 5.4) containing ferric chloride, all concentrations of olive oil polyphenols exhibited pro-oxidant effects. It appears that the reducing action of olive oil polyphenols accelerates oxidation of oil and especially of emulsions containing Fe (III) by reducing ferric ions to ferrous ions, which are effective pro-oxidants during storage.

The antioxidant activity of phenolic extracts from olives and olive oil has been assessed by scavenging of 1,1-diphenyl-2-picrylhydrazyl (DPPH) radicals and by studying the effects on the stability of stripped olive oil in the absence and presence of ferric chloride. The olive extracts contained a much higher concentration (1940±5800 mg kg À1) of phenolic components than the olive oil extract (180 mg kg À1 ). Some olive extracts were more effective than the olive oil extract in scavenging DPPH radicals, but the three varieties of olives examined showed relatively large differences in both polyphenol concentration and antioxidant activity of extracts. a-Tocopherol and extracts from both olives and olive oil were effective antioxidants in stripped olive oil at 60°C. Ferric chloride reduced the stability of stripped olive oil, but the olive extract studied was signi®cantly more effective as an antioxidant in the presence of the metal salt than the olive oil extract or a-tocopherol. Ferric ions catalysed the oxidation of caffeic acid, oleuropein and phenolic components of the olive and olive oil extracts in aqueous solution (pH 5.4). The olive extract oxidised more rapidly than the olive oil extract in aqueous solution.

In this study, carotenoids extracted from the yeast twenty different Rhodotorula glutinis strains (M1-M47) isolated from soil, plant, pine and tree leaves, grape, aubergine, pee, parsley and carrot were studied for their antibacterial and antioxidant activity. Carotenoid contents of Rhodotorula glutinis strains changed between 0.23 to 1.23 mg L-1. Most of the carotenoids extracted from Rhodotorula glutinis strains (sixteen out of twenty) showed both antioxidant and antibacterial effects. Carotenoids extracted from Rhodotorula glutinis strains No. 2, 25, 26 did not show any antimicrobial activity and strains No. 1, 33 and 41 did not show any antioxidant effect. Strain No. M38 (0.74 mg L-1) was not effective neither as antibacterial nor antioxidant. The results strongly suggested that the potential utility of carotenoid synthesizing yeast Rhodotorula spp as an alternative source of natural preservatives (antioxidant and antimicrobial), carotenoid pigments (colourants) and nutraceuticals.

Small ‘balls’ of yogurt cheese (40 g 100 g‐1 total solids), derived by extracting moisture from concentrated yogurt (23% total solids), can be stored in retail outlets in the Middle East (20–25°C) under virgin olive oil for up to two years. The absence of over‐acidification appears to be due to the inhibitory effect of low pH (3.8), low available water (0.85) and salt (1.0 g 100 g‐1) on starter activity, while the anaerobic conditions created by the oil both reinforce these inhibitory factors and, additionally, prevent the growth of yeasts over the surface of the individual balls. The type of vegetable oil covering the balls was found to be unimportant, and sunflower, safflower and cottonseed oil were equally effective in preserving yogurt cheese inoculated with Kluyveromyces marxianus subsp marxianus and stored for three months at 25°C.

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There are around 130 million olive trees in Turkey, of which 30 % is used for edible olive production and 70 % is used for olive oil production and 160,000 tons of olive oil is produced. Most of the production occurs in the Aegean, Mediterranean, Marmara and Southeastern Anatolia regions of the country 1-3. Turkey is one of the major olive oil producers and there are several studies about the chemical and analytical properties of Turkish olive oils from Ayvalik and Eastern Mediterranean cultivars 4. It is known that fats and oils undergo various deleterious changes including hydrolytic, oxidative, isomerization and polymerization reactions during heat treatment at elevated temperature. However, olive oil shows a high resistance to these non-desirable changes. The addition of antioxidants is one of the most well-known strategies applied to delay lipid oxidation reactions. Antioxidant compounds can increase shelf life by retarding the process of lipid oxidation during processing and storage of different lipid systems 5-7. Crude extracts can be refined to obtain concentrates with enhanced purity and antioxidant activity, suitable for specific food applications. The protective action of antioxidants has been frequently studied in oils, model foods, foods and cosmetic emulsions 8. The synthetic antioxidants such as butylated hydroxyl toluene (BHT) and butylated hydroxyl aniline (BHA) which are use is being restricted due to safety concerns have been widely used