Detection of tenderness, post-rigor age and water status changes in sheep meat using near infrared spectroscopy

The tenderness (objective measure is shear force) of sheep meat (longissimus thoracis et lumborum) during post-rigor ageing at 15 degrees C can be predicted using near infrared (NIR) analysis (r(2) = 0.85). Measurements (n = 260 from 65 lambs) were made at 0, 8, 24 and 72 h post-rigor using an interactance system operating over the spectral range from 400-1700 run. There was no predictive power in the NIR models to segregate tenderness measurements made at any one particular post-rigor time. NIR measurements could segregate the post-rigor ages with good accuracy (r(2)=0.91). The OH combination band at 840 nm is the dominant feature of the predictive models and suggests that the underlying chemistry is related to the post-rigor changes in the water status of the meat. Observations on another similar data set (n = 48 from 12 lambs), involving NIR and water content measurements, confirmed there are significant water changes in meat during aging. We speculate that the NIR models may be sensitive to the accumulation of free water arising from the degradation of cytoskeletal proteins during ageing, releasing the water normally tightly bound up in the tertiary protein structures.