Hyperspectral deep ultraviolet autofluorescence of muscle fibers is affected by postmortem changes.

After slaughter, muscle cells undergo biochemical and physicochemical changes that may affect their autofluorescence characteristics. The autofluorescent response of different rat extensor digitorum longus (EDL) and soleus muscle fiber types was investigated by deep ultraviolet (UV) synchrotron microspectroscopy immediately after animal sacrifice and after 24 h of storage in a moist chamber at 20 °C. The glycogen content decreased from 23 to 18 μmol/g of fresh muscle in 24 h postmortem. Following a 275 nm excitation wavelength, the spectral muscle fiber autofluorescence response showed discrimination depending upon postmortem time (t0 versus t24 h) on both muscles at 346 and 302 nm and, to a lesser extent, at 408 and 325 nm. Taken individually, all fiber types were discriminated but with variable accuracy, with type IIA showing better separation of t0/t24 h than other fiber types. These results suggest the usefulness of the autofluorescent response of muscle cells for rapid meat-aging characterization.