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The objective of this study was to determine the influence of quality grade (QG) and degree-of-doneness (DOD) on thermophysical properties of beef strip steaks. The “Prime” eating experience must be marketed to compete with cheaper protein sources, and so palatability is a major concern with beef products. Thermal and physical properties help shed light on the impacts various components have on beef palatability, mainly tenderness and juiciness. Warner-Bratzler shear force (WBSF) and the textural property of springiness are both influenced by a combination of QG and DOD. This is also true for viscoelasticity and the degradation of myosin and sarcoplasmic protein. Although many factors contribute to beef palatability, intra-muscular fat (IMF) content is usually given the most credit when presented to the consumer. However, QG only impacted raw steak weight, cooking duration, cohesiveness, and moisture interactions. DOD influenced more properties including cooking duration and cook loss percent conductivity, various textural properties, protein degradation (even before cooking), and moisture interactions. Generally speaking, these textural properties resulted in less favorable values as DOD increased, but that was not only the case. Thermal properties and protein degradation values simply showed unique differences between DOD (including refrigerated and room-temperature sampling) and did not always follow a trend. These results show that although over-cooking can be mitigated with high IMF content for tenderness, DOD has more of an effect on many of the palatability characteristics. Furthermore, more research will need to be conducted to fully understand the differences between some of our more intricate tests between QG and DOD.

This study determined how quality grade and degree of doneness influence the development of beef flavor compounds among whole muscle and ground patties. Proximate composition, pH, cooking duration, neutral and polar lipid fatty acids, free and total amino acids, total reducing sugars, and volatile compounds were evaluated in beef strip steaks and ground patties of Longissimus lumborum from three USDA quality grades (Prime, Low Choice, and Standard; n=8 per quality grade) and six degrees of doneness (4, 25, 55, 60, 71, and 77°C). In the split-plot experiment, quality grade was the whole-plot, product-type was a sub-plot, and degree of doneness was the sub-sub-plot. The 3-way interaction of quality grade, degree of doneness, and product type impacted moisture (P = 0.004) and protein content (P = 0.006); pH (P < 0.001); neutral and polar lipid fatty acids (P ≤ 0.048); free and total amino acids (P ≤ 0.044); total reducing sugars (P < 0.001); and volatile compounds (P ≤ 0.029). The 2-way interaction of quality grade and degree of doneness impacted free amino acids (P ≤ 0.036); PUFA within the neutral lipid fraction (P ≤ 0.033); fatty acids within the polar lipid fraction (P ≤ 0.043); volatile compounds (P ≤ 0.038); and the total fat percentage (P = 0.046). The 2-way interaction of quality grade and product type impacted fatty acids within the neutral lipid fraction (P ≤ 0.042); fatty acids within the polar lipid fraction (P ≤ 0.015); and volatile compounds (P ≤ 0.047). The 2-way interaction of product type and degree of doneness affected fatty acids within the neutral lipid fraction (P ≤ 0.046); fatty acids within the polar lipid fraction (P ≤ 0.035); free amino acids (P ≤ 0.005) and total amino acids (P ≤ 0.004); volatile compounds (P ≤ 0.029); and cooking duration (P < 0.001). Overall the results of this study indicated that quality grade, grinding, and cooking have interacting effects on flavor related compounds. Thus, each factor must be considered during any model development which aims to predict beef flavor.