Seasonal changes of connective tissue fluorescence in well-aged beef roasts, correcting for fat reflectance and signal source

Abstract

Thirty well-aged (30.3 ± 4.5 d) rib roasts were evaluated serially from January to August. A dual-channel fibre-optic probe measured fluorescence (F; excitation at 365 nm and emission from 410 to 550 nm) and reflectance (R; 550 nm) on the way-in (WI) and way-out (WO). Anatomical measurements were used to differentiate between signals exterior to the longissimus thoracis (EXLT) and intramuscular signals (INLT). Each roast was probed in eight locations, giving 32 sets of signals (position, WI or WO, EXLT or INLT). F peaks c-1 decreased serially with time, mean r = -0.47, P < 0.01. A ratio (F:R) was used to correct F signals for pseudofluorescence (upper edge of F excitation band-pass reflected from fat). This strengthened (P < 0.001) the mean correlation of F:R peaks cm-1 with time to r = -0.59, P < 0.001. F:R peaks cm-1 in EXLT and INLT were correlated, r = 0.24 for WI and r = 0.57 for WO, showing development of extramuscular and intramuscular connective tissues was linked ( P < 0.0005, n = 480). Key words: Beef, connective tissue, fluorescence, seasonal effect