Effect of connective tissue on the shape of reflectance spectra obtained with a fibre-optic fat-depth probe in beef

A fat-depth probe was fitted with optical fibres to combine depth detection with spectrophotometry and fluorometry. Measurements were made through forelimb flexor, triceps brachii and longissimus thoracis muscles on 22 beef carcasses in a meat cooler. All strong fluorescence peaks had matching strong reflectance peaks (presumably connective tissue), but some strong reflectance peaks did not have equivalent fluorescence peaks (presumably adipose tissue). When the probe stopped at full depth and a complete reflectance spectrum was obtained, no effect from adipose tissue at the optical window of the probe was detected, whereas connective tissue increased reflectance across the visible spectrum (P < 0.005). The strongest effect was at 600 nm. Thus, spuriously high reflectance readings obtained with a fibre-optic meat probe are more likely to originate from connective tissue than from intramuscular adipose tissue.