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Beef palatability can be described, altered, and optimized using three major characteristics: tenderness, juiciness, and ﬂavor. The manner in which meat is cooked can aﬀect each of these characteristics. Understanding the thermodynamics that occur during cooking can give important insight into ideal cooking parameters that would allow for optimizing beef palatability. The protein, fat, connective tissue and other materials that constitute beef will react diﬀerently depending on the cooking method and aﬀect the transfer of heat which in turn alters the texture, ﬂavor, and juiciness of the product. If a particular set of parameters such as steak thickness or grill surface temperature can be chosen to enhance the palatability of a steak of varying quality grade, then that product could be marketed more eﬀectively and consumed with higher acceptability thus increasing its value.
The objective of this project was to analyze the thermodynamics and physical properties of beef steaks of diﬀerent USDA quality grades, thicknesses, and grill surface temperatures cooked to the same internal degree of doneness to determine if a speciﬁc set of cooking parameters would create a profound diﬀerence in the eating characteristics of a steak.
Beef steaks of each quality grade (Upper 2/3 Choice and Select) and thickness (38.1mm thick and 17.6mm thin) were cooked on a ﬂat top grill with high (232.2°C) and low (176.7°C) surface temperatures. Steaks were cooked until they reached an internal degree of doneness (IDD) of 35°C and ﬂipped and further cooked until they reached an IDD of 71°C. Once at room temperature (25°C) the steaks underwent a series of tests which measured: cooking loss, change in thickness, percent expressible moisture, thermal conductivity and diﬀusivity, protein degradation, Warner‐Bratzler shear force (WBSF), texture proﬁle analysis (TPA), rheology, and protein degradation. Percent expressible moisture was measured using a centrifugal method, thermal measurements were simultaneously obtained using a Thermal Constant Analyzer (Hot Disk TPS‐500), WBSF and TPA were taken on a TSM‐Pro ﬁtted with a WBSF blade and parallel plate geometry respectively, rheological measurements were done using an AR‐G2 Rheometer, and the protein degradation enthalpies were obtained using a diﬀerential scanning calorimeter (DSC).
It was found that the interactions of quality grade with thickness (conductivity) and thickness with surface temperature (sarcoplasmic and actin enthalpy) indicate that surface temperature impacts thermal behavior, dependent on quality grade, while also inﬂuencing major protein structures. The thermal conductivity of steaks cooked with low surface temperature showed a diﬀerence between quality grades (P < 0.05) while high surface temperature steaks did not.
The elasticity of the surface and centers of the beef steaks were analyzed to determine how the microstructure of the beef responded to applied stress and to support that quality grade is a major eﬀector of thermal behavior due to the change in the microstructure and protein states. Steak center and surface elasticity modulus was inﬂuenced by the two‐way interactions of quality grade × steak thickness (P = 0.023 and 0.012, respectively).
The physical properties in the beef steaks further support through more tangible applications that the composition, thickness, and cooking regiments impact the microstructure and thermal properties of beef and thus ﬁnal tenderness and texture.
This project identiﬁed that quality grade has an impact on how heat transfers through beef and the microstructure and textural properties are further altered by the cooking surface temperature. Cooking preparation should take into consideration that quality grade, thickness and cooking temperature will aﬀect the textural eating qualities of beef steaks. Choice thick steaks cooked at low surface temperatures were shown to be juicier and more tender then Select thin steaks, but Select steaks cooked at high surface temperatures had comparable characteristics to Choice steaks. Therefore, cooking parameters may be utilized as a mechanism to enhance beef steak palatability.
Figure 1. Sarcoplasmic and actin protein degradation of thick (38.1mm) and thin (17.6mm) beef strip steaks from two quality grades (USDA Choice and Select) cooked with high (232.2°C) and low (176.7°C) grill surface temperatures. Two‐way interaction of USDA quality grade × thickness was observed (P = 0.002). Error bars represent pooled (largest) SEM. ab Columns lacking a common super script differ (P < 0.05).
Figure 2. Conductivity of thick (38.1mm) and thin (17.6mm) beef strip steaks from two quality grades (USDA Choice and Select) cooked with high (232.2°C) and low (176.7°C) grill surface temperatures. Two‐way interaction of USDA quality grade × grill surface temperature was observed (P = 0.048). Error bars represent pooled (largest) SEM. ab Columns lacking a common super script differ (P< 0.05).
Figure 3. (a) Example of a thermogram plot of sarcoplasmic and action protein degradation enthalpy from the differential scanning calorimeter, (b) example of how the HotDisk sensor would be placed in a steak sample for determination of thermal conductivity, diffusivity, and heat capacity.