Effect of Different Processing Methods on the Chemical Composition, Antioxidant Activity and Lipid Quality of Tiger Nuts ( Cyperus esculentus )

The objective of this study was to evaluate the effect of single and coupled processing methods on the chemical composition, Antioxidant Activity and Lipid Quality of Tiger Nuts (Cyperus esculentus L). The processing methods applied were oven and sun drying, boiling water, steaming, blanching and roasting. After processing, tiger nut powders were analyzed for their total phenolic content, antioxidant activity, oil quality, nutrients and anti-nutrients composition. Results showed that boiling and blanching significantly (p<0.05) reduced the total phenolic content of tiger nuts (24.66 to 20.17 mg GAE/100 g for boiling and 39.23 to 30.26 GAE/100 g for blanching) while this parameter increased with roasting (40.73 to 300.44 mg GAE/100 g). Drying coupled to roasting significantly (p<0.05) increased the antioxidant activity (from 11.00-17.40 to 56.34-96.33%) of the nuts. The analysis of oils showed that the treatments applied significantly (p<0.05) increased its peroxide (PV) (from 1.69 to 21.31 meq O-2/Kg) and thiobarbituric acid (TBA) (0.32 to 3.77 ppm) values. Oil from roasting for 10 min was the most altered with PV and TBA values of 21.31 meq O-2/Kg and 2.23 ppm, respectively. The analysis of the proximate composition showed that the processing methods used have significantly (p<0.05) reduced the carbohydrate (from 52.13 to 36.57%) and protein (from 11.73 to 4.58%) contents of tiger nuts while the lipid content increased (from 26.49 to 42.56%). Processed Tiger nuts were found to be rich in phosphorus, sodium, potassium, calcium and magnesium. All the processing methods have significantly reduced (p<0.05) the anti-nutrient content of tiger nuts.