Use of Polyphenol Extracts from Dioscorea steriscus and Plecranthus esculentus N.E.Br Tubers to Curb Oxidative Deterioration of Sunflower Oil
Published: 2020-03-25
Page: 18-28
Issue: 2020 - Volume 3 [Issue 1]
Masimba Tapera *
Department of Chemistry, School of Pure and Applied Sciences, Kenyatta University, P.O.Box. 43844-00100, Nairobi, Kenya and Department of Physical Science, Science Technology Division, Harare Polytechnic, P.O.Box CY 407, Causeway, Harare, Zimbabwe.
Ruth Wanjau
Department of Chemistry, School of Pure and Applied Sciences, Kenyatta University, P.O.Box. 43844-00100, Nairobi, Kenya.
Alex K. Machocho
Department of Chemistry, School of Pure and Applied Sciences, Kenyatta University, P.O.Box. 43844-00100, Nairobi, Kenya.
Pamhidzai Dzomba
Department of Chemistry, Faculty of Science, Bindura University of Science Education, P. Bag 1020, Bindura, Zimbabwe.
*Author to whom correspondence should be addressed.
Abstract
Aim: The aim of the present study was to determine the possibility of using polyphenol extracts from Dioscorea steriscus and Plecranthus esculentus N.E.Br tubers of Zimbabwe as preservatives for sunflower oil under oven and kitchen storage conditions.
Methodology: Polyphenols were extracted from Dioscorea steriscus and Plecranthus esculentus tubers, screened using polyphenol screening assays and added to virgin sunflower oil at 100 ppm dose. Oxidative stability was determined using peroxide values and UV-Vis absorbances a 232 nm.
Results: Polyphenol screening assays of aqueous acetone extracts from Dioscorea steriscus and Plecranthus esculentus tubers revealed the presence of flavonoids, phenolic acids, tannins, lignans and anthocyanins. Oxidative stability of sunflower oil under kitchen storage conditions (room temperature) and oven storage conditions (65°C) as measured by peroxide values and UV-Vis absorbances at 232 nm followed the order D. steriscus fortified ˃ BHT fortified ˃ P. esculentus fortified ˃ unfortified. The lowest mean peroxide value (17.72±0.05 mEq/kg oil) over a 5 week storage duration under kitchen storage conditions was recorded in D.steriscus fortified sunflower oil and the highest (31.17±0.16 mEq/kg oil) was recorded in unfortified sunflower oil.
Conclusion: Polyphenol extracts from Dioscorea steriscus and Plecranthus esculentus tubers showed high preservative potential on virgin sunflower oil under both kitchen and oven storage conditions. Polyphenol extracts from D. steriscus and P. esculentus tubers may be used as alternative sources of antioxidants for the preservation of sunflower oil.
Keywords: Antioxidants, edible oils, peroxide value, polyphenol, Dioscorea steriscus, Plecranthus esculentus.