A new spectrophotometric method for the rapid assessment of deep frying oil quality

A new and quick spectrophotometric method was developed to assess deep-fryi ng oil quality. The scanned spectrophotometric curves of the frying oil sam ples from 350 and 650 nm wavelength changed systematically with the duratio n of deep frying. The absorbances of the frying oil samples, especially tho se measured at 490 nm, increased significantly during frying and were signi ficantly correlated to frying time (I greater than or equal to 0.95, P < 0. 001). There was a strong correlation between the absorbances of a set of oi l samples taken from 0 to 80 h of deep frying and total polar compound cont ents in the same set of oil samples analyzed using the American Oil Chemist s' Society official method (r = 0.924, P < 0.001). The equation for convers ion of the absorbances to total polar compound contents is y = -2.7865x(2) + 23.782x + 1.0309. The absorbances of 10 different types of frying oils wi th samples taken from 0 to 80 h of deep frying in duplicate were also stron gly correlated to total polar compounds in the same oil samples (r = 0.953, P < 0.001, n = 220). The results show that this method is fast, simple, co nvenient, and reliable.