Infrared Fiber Optic Spectrophotometry of Meat

Abstract

The absorbance of infrared light (700 to 1,000 nm) by the bovine longissimus muscle and by porcine vastus intermedius and semitendinosus muscles and subcutaneous adipose tissue was measured with a fiber optic probe. The primary objectives were: (1) to identify an optimum wavelength for the optical resolution of boundaries between adipose tissue and lean meat and (2) to examine the relationship between infrared absorbance and pH-dependent aspects of meat quality. The widest separation of the absorbance spectra of fat and lean was at 850 nm. The difference between muscle and fat was less pronounced at lower and higher wavelengths. The difference was enhanced when muscles were pale, soft and exudative (PSE). However, the wavelength that was best suited for the detection of boundaries between muscle and fat (850 nm) was the least suitable for the detection of PSE. Absorbance at 1,000 nm was correlated with several indices of the PSE condition: with electrical resistivity (r = −.83, P<.005), with capacitance (r = −.66, P<.01) and with pH at 45 min postmortem (r = −.63, P<.025). However, similar relationships were also found with red light at 700 nm.