Estimation of quality attributes and frying times of cottonseed and sunflower oil blend during deep-fat frying of potato chips

ABSTRACT

The chemical, physical and some sensory changes induced upon deep-fat frying of potato chips in a blend of cottonseed and sunflower oil were investigated. The chemical changes were correlated with the frying times aiming at establishing prediction models for estimating frying times. The oil blend became dark in colour after each successive frying. The correlation coefficient between the frying time and A[400] was very high [r=0.9967]. Similar trend was also observed in the relationship between the frying times and A[450-] Oil viscosity increased significantly with increasing frying times indicating evidence of thermal decomposition of frying oil blend. The correlation coefficient between the frying times and the refractive index was high [r=0.9898]. Slight and Continuous losses in unsaturated fatty acids of the oil blend during deep-fat frying of potato chips have taken place. The peroxide value [meq O[2]/kg oil] increased initially from 3.86 to 11.81 after 10 fryings, then dropped to 5.23 after 20 fryings followed by another rapid increase to 19.76 [meq. O[2]/kg oil] after 30 fryings. The UV absorption at 232nm increased initially from 0.4 to 1.5 after only 5 fryings and unchanged from the 5th frying to the 20th frying then dropped after 30 fryings. A considerable increase in the TBA value has occurred up to the 20[th] frying and then the TBA value showed no change for the next 10 fryings. The correlation coefficient between the frying time and TBA value was 0.93. The rate of polar compounds formation for the first 5 fryings was 3.62 mg/100mg oil/hr. whereas from the 5[th] frying to the 30[th] frying such rate was reduced to only 1.12 mg/100mg oil/hr. Sensory evaluation of the oil blend indicated that odour and colour scores were inversely related to the frying time. The most important and accurate mathematical models which express the relationship between the independent and dependant variables were established, The frying time could be successfully and accurately predicted by wise and intelligent chose of dependant variables incorporated in the best lit equations