| Popis: |
Background: Lipid oxidation is responsible for the deterioration of the nutritional and organoleptic qualities of foods. It also leads to the formation in these products of compounds which are harmful for the consumer's health. The synthetic antioxidants used by industries in order to solve this problem are also prone to be toxic and quite volatile at high temperatures. On the other hand, the trend among researchers to replace the synthetic antioxidants with natural ones is increasing because of their potential health benefits. In this study, old Cameroonian green tea leaf methanolic extracts were added in palm olein and its efficiency in delaying the oxidation of oil under forced storage conditions was assessed. Methods: The plant material was extracted with methanol and its total phenolics content evaluated by colorimetry, followed by the qualitative identification of some phenolic antioxidants by HPLC-DAD and ESI-MS. After preliminary antioxidant studies, the extract was added in oil at concentrations that ranged from 200 to 1800 ppm. Oil containing butylated hydroxytoluene (BHT) and oil without antioxidant served as positive and negative controls, respectively. The oxidative stability of these oil samples was evaluated by determining their oxidation induction times on Rancimat (at 110 °C) and measuring their oxidative state by the Schaal oven test method during 30 days of storage at 70 °C. Here, oil samples were collected every 10 days and their peroxide, p-anisidine, total oxidation, thiobarbituric acid, iodine values as well as changes in their linoleic acid profile gas chromatography coupled to flame ionization detector (GC/FID) were evaluated. Results: The outcomes showed the total phenolics content of the extract to be 53.5 mg GAE/g. Gallic acid, epicatechin gallate, gallocatechin and epigallocatechin gallate were the phenolic antioxidants detected. The induction times of palm olein supplemented with the extract (200–1800 ppm) were found to be in the range of 24.8–28.9 h, while those of control and oil containing BHT were 20.1 and 22.7 h, respectively. The extracts, at all concentrations, were also found to be efficient like butylated hydroxytoluene in inhibiting the oxidation of palm olein during 30 days of storage at 70 °C. Conclusion: The investigations showed that old Cameroonian green tea leaves are a viable source of natural antioxidants for delaying palm olein oxidation. |
