The dynamics of a canola based shortening degradation was studied by measuring the concentrations of major degradation products-polymers, decomposition products, free fatty acids and total polar materials and optical properties. The effects of these degradation products were highly significant (P<0.0001) on turbidity, lightness and photometric colour index. No significant change was observed in the refractive index of the samples. The turbidity decreased with frying time due to the increase in the fat darkness. Transmittance showed high correlations with all the major degradation products only between 550 and 695 nm wavelengths. The redness increased gradually until 5th day of frying and decreased afterwards due to increase in darkness. Similarly, yellowness and chroma increased until day 3 and decreased steadily after that. Lightness decreased and photometric colour index increased with increase in frying time and correlated well with major degradation products.