Multiplicative Scatter Correction of Visible Reflectance Spectra in Color Determination of Meat Surfaces

Abstract

Due to inhomogenous surfaces, differences in light scatter and a variable fat-to-meat ratio in the limited area hit by the incident light beam, the instrumentally evaluated color parameters of dry sausage exhibited unacceptable high standard deviations. Color parameters from cut surfaces were evaluated from reflectance spectra in the region 380–760 nm, measured by a scanning spectrophotometer fitted with an intergrating sphere. The spectra were transformed to the C.I.E. 1976 L*a*b* color system. Twenty-nine replicates were examined, and although it was impossible to differentiate them visually, even at different light conditions, the L*a*b* values ranged by as much as 7, 3.3, and 2.8 units, respectively. The MSC transformation compensates linearly for both additive and multiplicative optical effects in the data. It alters neither the mean reflectance spectrum nor the mean color values, but it reduces variations between replicates considerably. As expected, the SD in lightness, L*, was most affected, with a decrease by a factor 5.2, while the SD in redness-greenness, a*, and blueness-yellowness, b*, decreased by factors 2.3 and 1.7, respectively.