Calculation and presentation of pork muscle colour from reflectance spectra

Abstract

AbstractPale and dark longissimus dorsi muscle samples with the surface pigments predominantly in the reduced, oxygenated, or oxidised form, were used to determine the effects of the shape and position of the reflection spectra on four mathematical techniques for expressing colour in C.I.E. terminology.No significant differences in the computation of tristimulus values were obtained by the weighted ordinate method, using 5 and 10 nm intervals, and the thirty and ten point selected ordinate method. The latter method provides a quick and convenient method of calculation. A chart has been constructed for the direct conversion of x and y co‐ordinates to dominant wavelength (λd) and percentage purity values, the x/y calculation for λd being read to less than 1 ran and for purity to less than 1%.A nomogram to convert C.I.E. brightness (Y tristimulus value) to Munsell value has been produced for the 10‐40Y range; it has an error of less than 3%. A series of four charts has been prepared, with which muscle colour, calculated in terms of C.I.E., can be defined in Munsell notation. The conversion error is maintained below visually perceptible steps. These charts extend the usefulness of reflection spectrophotometers in measuring the colour of pork.