Abstract:
Palm olein was blended with three Sudanese edible oils namely cottonseed, groundnut, and sunflower oils, at two levels (3:1; 1:1, respectively), to evaluate the effect of these oils on palm olein stability during storage and as influenced by the frying process. The viscosity, color, refractive index (R.I), free fatty acids (FFA), peroxide value (PV), polymer content (PC) and iodine value (IV) of the blends were monitored during both storage intervals of 0, 3, 6 and 12 months, and exposure to frying temperature at 180 ± 20C for 5, 10 and 15hrs. During storage of the palm olein blends for 12 months, it was found that the degradation of the triglycerides of palm olein blends 1:1 mixing level into FFA particularly of groundnut oil blends was significantly (P?0.05) higher than the pure palm olein (6.51 and 4.30%, respectively). However, the FFA of palm olein blends of cottonseed oil and sunflower oil at high olein level (3:1) showed no significant (P?0.05) changes compared to the pure palm olein. The stability of palm olein containing conventional oils has significantly (P?0.05) decreased with all blends, as shown by high level of peroxides (PV above 15 meq.O2), compared to the pure palm olein (9.17 meq.O2). The polymer formation in all palm olein blends of 1:1 ratios has significantly (P?0.05) increased (PC ranged between 6.13 and 8.00%) compared to the pure palm olein (3.8%). After 15 hrs of exposure to frying temperature, palm olein blends containing low level of Sudanese oils were more stable as shown by less split in FFA (2.59%) compared to higher ones in high level of these oils in olein (3.34%).Similarly, the formation of peroxides was lower during frying of olein of low blending level (PV ranged between 8.06 and 8.80 meq.O2) compared to the one containing high level of Sudanese oils (10.44 to 14.19 meq.O2). Equally, the formation of polymers was faster and higher in high blending levels (PC ranged between 5.84 and 7.44%) compared to lower levels (3.84 to 5.42%).
