Tenderness has been shown to be the most important factor affecting consumer satisfaction for beef. The most commonly used method to predict beef tenderness is USDA quality grading, but that system is not completely accurate as it only reflects a compilation of traits that are indicators of tenderness.
During recent years, the beef industry has examined instrument grading for its potential to improve objectivity of palatability and cutability predictions. Employing technology has shown promise in increasing the ability to more accurately sort carcasses into quality groups. Researchers have developed several instrument grading systems, but widespread commercial adoption has still not occurred.
In order for a tenderness prediction system to be accepted in a commercial setting, it must meet the following guidelines:
Researchers at Oklahoma State University developed a spectrometric grading instrument that meets these criteria in a laboratory setting. The objective of this project was to evaluate the system in a packing plant environment by 1) developing a portable system to collect nearinfrared spectral reflectance values from fresh meat at three days postmortem and 2) developing chemometric models to relate spectral reflectance to 14-day shear force tenderness measurements.
During the first phase of the project, 292 carcasses were selected at the USDA grading stand, approximately 48 hours postmortem. The following factors were collected for each carcass:
In both phases of the investigation, slice shear force values exceeding 25 kilograms were greater for the Select quality samples—nine percent—versus only 3.4 percent and 5.9 percent tough samples from Choice carcasses in Phases I and II, respectively. There was substantial variation in tenderness for the entire population, with a range in slice shear force from 9.87 to 39.87. In fact, 12 ribeye samples had slice shear force values that exceeded 28 kilograms in toughness.
In the initial phases of the project, 39 of the 568 carcass samples were categorized as tough (≥ 25-kilogram slice shear force at 14 days of postmortem aging). This reflects a 6.8 percent error in certification at the 100 percent level. A very high percentage of the samples were correctly classified as tender when the population was categorized into expected certification levels. Of the 39 tough samples, 20 (3.7 percent error rate) were correctly placed in the 90 percent certification level. Another 10 tough samples were placed in the 80 percent certification level. (2.0 percent error rate).
Fifty-seven samples were spectrally predicted to be the most tender. The mean slice shear value for this group was 14.90 kilograms and no tough samples occurred in this set. In other words, the spectral reflectance accurately predicted the steaks’ tenderness and did not erroneously group a tough steak into the “certified tender” group. The overall mean for the samples predicted as “toughest” was 24 kilograms with 20 of the 39 tough samples being correctly placed in this category.
Regardless of percentage certified, the difference in mean longissimus slice shear force value between “certified tender” and “not certified” was significant (P < 0.05) for spectral analysis. Removing the toughest 10 percent improved the mean slice shear force of the group more than 6.5 kilograms. In other words, when predicted tough samples were removed from the population, improvements were made in the “certified tender” population.
Utilizing the 60 percent certified as tender as a sorting tool for eliminating tough carcasses, improved slice shear force values in excess of 4.0 kilograms. In fact, an improvement in excess of 32 percent was observed in the slice shear force values between the extreme 10 percent certified (14.80 kilograms) and not certified (21.56 kilograms) categories.
One of the biggest hurdles to the adoption of instrument grading at the commercial level has been the degree of inaccurate predictions that are produced by many of the current systems available. Based on this project, the spectral reflectance predictions appeared to offer more consistent readings.
Segmenting carcasses based on their projected slice shear force value as estimated by spectral readings appears to be an effective tool for sorting carcasses into relative quality groups, especially carcasses from lower quality grades. The ability to more accurately sort carcasses for tenderness can be hugely beneficial in marketing programs that promise consumers tender beef on a consistent basis.