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Aims: The present study was performed in order to test the effect of different concentrations of tea leaves methanolic extracts on the oxidative stability of palm olein subjected at frying temperature.
Study Design: Harvesting of fresh tea leaves, cleaning and drying, extraction of natural antioxidants, supplementation of refined palm olein with the extract and evaluation of its stability during storage at frying temperature (180 ± 5°C).
Place and Duration of Study: University of Dschang, Cameroon and Council for Scientific and Industrial Research-Indian Institute of Chemical Technology (CSIR-IICT), Hyderabad, India, from July 2015 to December 2015.
Methodology: The natural antioxidants were extracted by macerating dried green tea leaves in methanol. The concentrated extract was then added in refined palm olein without additives at concentrations 200, 600, 1000, 1400 and 1800 ppm respectively. Oil containing butylated hydroxytoluene (BHT) and oil without antioxidants served as positive and negative controls respectively. The oil samples were then stored in the oven at 180°C for 6 consecutive days (4 hours heating/day). After every two days of heating, oil samples were collected and various chemical parameters (peroxide value, p-anisidine value, thiobarbituric acid value and iodine value were measured) and instrumental techniques (Gas-chromatography) were used to test the oil deterioration that permit the distinction of oxidative alteration level during storage.
Results: Quantitative measurements revealed significantly (p<0.05) higher rate of oxidative alteration level in Control and PO+BHT200ppm (palm olein supplemented with butyl hydroxytoluene) during the storage compared to oil samples containing tea leaves extract as natural antioxidant. At all concentrations, tea extract was very efficient than butylated hydroxytoluene (BHT). It was also the best in delaying linoleic acid degradation during the process.
Conclusion: From these results, it can be concluded that green tea leaves are rich in natural antioxidants of good thermal stability, which can be exploited to delay the oxidation of palm olein during processing at high temperature and during storage.