Evaluation of Capsicum as a Source of Natural Antioxidant in Preventing Rancidity in sunflower Oil
2002
Elizabeth Maforimbo
Solvent extraction to obtain oleoresins of flavonoid and carotenoid extracts was done from 200 grams of commercial paprika powder. Petroleum ether was used to defat the sample. Methanol and n-butanol were used in turn to extract the polar flavonoids, while chilled acetone and petroleum ether were used in turn for the extraction of nonpolar carotenoids. The flavonoid yield was 5.92grams while that for the carotenoids was 39.15 grams per 100g of the powder. These residues were tested on sunflower oil to evaluate their antioxidant effects. The accelerated methods used for oxidation were the Automated Rancimat, Oven heating and UV light at 254 nm. The oxidation of sunflower oil was measured using changes in peroxide values and the UV absorbances (Conjugated diene) at 232 nm, E1%1cm. The extracts tested possess antioxidant effect and this phenomenon was enhanced by increasing their concentration, since they were impure. The major components of paprika (b-carotene and capsanthin) were also tested on the oil as pure standards while Butylenehydroxytoluene (BHT) was used as a standard antioxidant. Results showed that carotenoids seemed to be effective in retarding oil peroxidation under photoxidation, while showing pro-oxidant activity under oven heating autoxidation, and showing slight antioxidant activity under Rancimat autoxidotion tests. The flavonoids were effective in retarding oil oxidation under both photoxidation and thermal autoxidation tests, with the column separated fractions 3 and 4 conferring better antioxidant activity under the Rancimat test. These column separated fractions, were identified by the UV Spectra as 3-hydroxyflavanones or dihydroflavonols.
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