Effect of level of palm olein on the frying quality and stability of groundnut oil

The effect of blending groundnut oil and palm olein at different levels on the frying quality and stability of the former oil was studied. The two oils were blended at 70 to 30% and 50 to 50% ratios of groundnut oil to palm olein, respectively. Oil blends against of single oils were used in frequent frying of potato chips. Abused oils were then stored for different length of times (12, 40 and 96 days) at room temperature (37= 3 deg C). Physiochemical changes in oils as affectd by both frequent frying and storage were monitored together with sensory characteristic of oils and potato chips. Significant increases (P0.05) in the physical constants of oils (e.g. viscosity and refractive index) were observed by frequent frying. As for the stability values, groundnut oil recorded the highest peroxide value (from 11.1 to 31.1 m.Eq/kg oil), free fatty acids (from 0.023 to 0.23% oleic), and polumer content (from 0.53 to 2.44%) compared to minimum values recorded for palm olein (from 9.1 to 15.9 m.Eq/kg oil: 0.13 to 0.23% palmitic: 0.33 to 0.58% polymer, respectively). The oil blends recorded respective values in between. Organoleptic quality of potato chips fried in blends was significantly (P0.05) superior followed by chips fried in groundnut oil, while chips fried in palm olein were least acceptable. Oils used in frying also gave same sequence of organoleptic acceptabilities. Stability values were significantly (P0.05) increased during storage of abused oils. The peroxide value of bused groundnut oil increased from 39.1 m.Eq/kg oil in 12 days to 148 m.Eq/kg oil in 96 days, against extremely lower values recorded for abused palm olein (17.2 to 22.3 m.Eq/kg oil, respectively) for the same storage period of time. Significant (P0.05) increases were also recorded for free fatty acids in abused groundnut oil for both medium and prolonged storage (from 0.5 to 0.8% oleic, rspectively) compared to values recorded for abused palm olein (0.54 to 0.63% palmitic). Polymer content of abused oils also increased significantly (P0.05) where abused groundnut oil recorded the maximum (from 6.3 to 7.7%) and abused palm olein recorded the minimum (from 1.26 to 4.31). With values in between recorded for abused blends. Abused oil blends remained organoleptically superior during medium storage followed by abused groundnut oil, however, the latter oil exhibited obvious rancid odour at the end of the prolonged storage