MICROWAVE TREATMENT OF GROUNDNUT (ARACHIS-HYPOGAEA) - EXTRACTABILITY AND QUALITY OF OIL AND ITS RELATION TO LIPASE AND LIPOXYGENASE ACTIVITY

The microwave (MW) treatment of groundnuts for different periods (30 t o 360 s) indicated that treatment for a short period of 30 s increased the oil recovery from 276 +/- 12 to 300 +/- 17 mL/kg, then decreasing relatively when subjected to longer period of treatment i.e. 360 s. I n general, oil recovered from MW-treated samples showed higher free fa tty acid content and peroxide value, when compared to oil recovered fr om untreated sample. The storage of oil at 27 degrees C for 70 d showe d a greater increase in free fatty acids in the samples treated for sh orter- period of up to 120 s, whereas the PV showed a greater increase after longer periods of MW treatment. The oil extracted from the samp le MW-treated for more than 180 s had an undesirable dark colour. The protein extractability decreased to 58 +/- 1 g/kg from 84 +/- 2 g/kg i n 360-S MW-treated groundnut. A gradual decrease in the activity of th e enzymes lipoxygenase and lipase was observed with an increase in the period of MW treatment resulting in an inactivation of 35 +/- 0.3 and 78 +/- 0.1% respectively for 300-s MW-treated groundnut.