The Effect of Scanning Angle on Measured Reflectance and Tenderness Prediction in Beef Longissimus Thoracis Steaks

Near-infrared (NIR) reflectance spectroscopy has previously demonstrated potential to quantify tenderness and sensory attributes of meat. The objective of this study was to test the effect of scanning angle on visible/near-infrared (VNIR) spectral reflectance and the ability of reflectance spectra to predict tenderness of longissimus thoracis (LT) steaks. Two experiments were conducted to evaluate the effect of scanning angle configuration on steak reflectance. The first experiment included 60 steaks from two quality grades, aged for either 7 or 14 d, which were randomly assigned to two treatments in which the steak angles with respect to the light and sensor were changed. In the second experiment, 16 steaks from the two quality grades were scanned at six different angles. The Warner-Bratzler shear force (WBSF) was measured as a quantitative measure of tenderness. There were significant amplitude differences of up to 50% in the average reflectance spectra between the two treatments in experiment 1, and up to 200% difference between the reflectance spectra when the steak was tilted from 30° counterclockwise to 30° clockwise. First derivatives of the reflectance spectra also showed significant differences with respect to scanning angle. Chemometric models on VNIR spectra could predict only 19% of the variability in tenderness when the scanning angle was not considered. However, when individual models were developed for each scanning angle-aging group, the models accounted for 20% to 86% of the variability in tenderness. This study, with its limited data and tenderness ranges, showed that scanning angle is an important factor affecting the accuracy of reflectance-based tenderness models.