Optical properties of turkey pectoralis muscle affecting detection of connective tissue fluorescence

Abstract

A dual-channel probe was used to detect fluorescence (excitation 365 nm, emission 400 to 550 nm) and reflectance (550 nm) in turkey pectoralis muscles (n= 157). All fluorescence peaks had matching reflectance peaks, but not vice versa. Thus, some reflectance peaks originated from non-fluorescent structures in the muscle. Electrical impedance was used to assess fluid distribution. Electrical capacitance was correlated (P< 0.01) with areas under probe signals (r= 0.19 for both fluorescence and reflectance). In a subset of samples (n= 45), the reflectance of initially polarized light was used to assess light scattering. Consistent relationships between probe signals and the reflectance of initially polarized light were detected. When polarized light was parallel with the longitudinal axes of muscle fibers, and when the analyzer was parallel with the polarizer, reflectance was correlated (P< 0.01) with the incidence of fluorescence and reflectance peaks (R= 0.58 and R= 0.59, respectively), with mean peak intensity (R= 0.51 and R= 0.49, respectively), and with mean half-peak width (R= 0.48 and R= 0.56, respectively). The spectral distribution of correlations indicated that myoglobin as well as differences in light scattering affected the probe detection of connective tissue fluorescence. Thus, bulk optical properties of muscle affected probe detection of connective tissue fluorescence. Key words: Connective tissue, fluorescence, turkey meat