QUALITY EVALUATION OF TIGERNUT (Cyperus esculentus L.) OIL - EFFECT OF PROCESSING PRETREATMENTS

Vegetable oil is an essential component of cooking globally. The craving for healthier lipids informed the need to consider and evaluate the quality of oil from underutilized edible oil seeds or nuts like tiger nuts (Cyperus esculentus). This study evaluated the quality attributes of tiger nut, a major nut cultivated across Africa and enriched with about 22.14-44.92% oil. Applying completely randomized design, oil was extracted mechanically from the nuts using an oil expeller and the impact of variety (yellow and brown), moisture level (7%, 10% and 13%), toasting temperature (50°C, 70°C, 90°C) and toasting time (10, 20 and 30 min). Using standard procedures, 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 that the FFA ranged from 0.2243-0.486%, IV from 52.624-80.201 (mg/100g), PV from 2.183-4.52 (meq/kg), RI from 1.448-1.473, and RD ranged from 0.912-0.977. FFA and PV increased as the moisture level, toasting time and temperature increased, whereas the IV decreased. 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. Though the interaction of factors does not have significant effects on the RI. Tiger nut oil was observed to be golden yellow in color and was free of rancid odor and taste. The results show that tiger nut oil has comparable characteristics to common vegetable oils used in food related applications and can be considered a competitive lipid for food preparation anywhere.