Tiger Nut (Cyperus esculentus L.) oil quality evaluation as affected by variety and processing conditions

Abstract

Article InformationTiger nuts (Cyperus esculentus) are underutilized edible oil seeds cultivated across Africa with potential as a source of healthy vegetable oil. It is rich in oil with about 22.14 -44.92% of the dry weight. This study's main aim was to evaluate the quality of tiger nut oil and determine the best variety and processing conditions for producing high-quality from it to meet the increasing demand for healthier and more sustainable vegetable oils. Applying a completely randomized design, oil was extracted mechanically using an oil expeller and the impact of variety (yellow and brown), moisture level (7%, 10% and 13%), toasting temperature (50 °C, 70 °C and 90 °C) and toasting time (10, 20 and 30 min) were investigated. Using standard procedures, five oil quality parameters were determined, namely free fatty acid (FFA), iodine value (IV), peroxide value (PV), refractive index (RI) and relative density (RD). The result shows a range of 0.22 -0.49% for FFA, 52.62 -80.20 (mg/100g) for IV, 2.18-4.52 (meqO2/Kg) for PV, 1.45 -1.47 for RI, and 0.91 -0.98 for RD. FFA and PV all increased as the moisture level, toasting time and toasting temperature increased, whereas the IV decreases. The RI and RD values decreased as the toasting temperature and toasting time increased but increased as the moisture level increased. ANOVA indicates that variety, moisture level, toasting temperature and toasting time have significant effects on the FFA, IV, PV, RI and RD at P ≤0.05. The results show that the best oil quality was achieved at 7 % moisture content, 50 °C toasting temperature and 10 min toasting time for both varieties. The brown tiger nut has more quality oil than the yellow Tiger nut. The tiger nut oil has comparable characteristics common to vegetable oils used in food related applications and can be considered a viable alternative to common vegetable oils for food preparation. Findings from this study will help tiger nut oil processors to make the right processing pretreatment before oil extraction.