Use of Noncontact Diffuse Reflectance Spectroscopy and Optical Coherence Tomography Techniques to Characterize Both Spectral Reflectance and Internal Backscattering of Beef Psoas Major and Longissimus Lumborum Muscles

The rate at which meat discolors varies by muscle type. However, currently, there are no noncontact methods available to characterize inter- and within-muscle differences in color stability. The objective of this study was to assess whether combining reflectance and scattering-based properties helps differentiate intermuscle differences in color stabilities better than using reflectance. This study assessed both the surface myoglobin forms using noncontact diffuse reflectance spectroscopy (DRS) and internal backscattering characteristics using optical coherence tomography (OCT) to understand intermuscle differences affecting the color stability between beef psoas major (PM) and longissimus lumborum (LL) muscles. Surface color measured using a contact HunterLab MiniScan colorimeter and noncontact DRS, and depth- resolved backscattering imaged by OCT, was conducted on PM and LL Choice steaks from day 0 to day 4 of retail display. The colorimetric measurement indicated that [Met]% in PM (LL) increased from 22.8 ± 10.1% (20.7 ± 13.2%) on day 0 to 49.2 ± 14.8% (27.1 ± 13.1%) on day 4 (P < 0.0001). The noncontact DRS assessed that [Met]% of the PM (LL) increased from 6.6 ± 21.1% (6.9 ± 25.1%) on day 0 to 47.8 ± 28.8% (14.5 ± 28.8%) on day 4 (P < 0.0001). The OCT revealed that there was a muscle type × storage time interaction in the rate of signal decay (4.3 ± 1.2dB/mm for PM versus 6.9 ± 1.2dB/mm for LL, P < 0.0001) as well as a muscle type main effect difference in the depth of penetration between PM and LL (P < 0.0001). The depth-resolved backscattering properties accessible by OCT provided imaging evidence of morphological differences in PM and LL muscles, supporting different rates of [Met]% progression in retail display. The current study indicates that the use of DRS (reflectance) and OCT (scattering) will provide information about meat color changes and morphological features of meat.