Post-mortem spectrophotometry of pork and beef using quartz optical fibres

A high intensity xenon illuminator, a diffraction grating monochromator and a photomultiplier were linked to pork or beef samples with a bifurcated light guide composed of quartz optical fibers in a random pattern. When muscle fibres and optical fibres were parallel and coaxial, absorbance was greater than when they were perpendicular. As judged by the coefficient of variation at different wavelengths, the effect of fat in the measuring field was not uniform at all wavelengths. For the study of optical changes in pork, from slaughter to 24 h, the fibre-optic probe was maintained in a stationary position. The changes detected were: (1) a slight transient increase in absorbance at all wavelengths in the first few hours post mortem, (2) an eventual decline in absorbance at all wavelengths to reach minimum values at 24 h and (3) a spectrally limited decrease in absorbance, peaking somewhere in the 390 to 450 nm range, which started immediately post mortem.