Master of Science / Department of Animal Sciences and Industry / Travis G. O'Quinn / The objective of this research was to evaluate the role of marbling texture on beef palatability, muscle histology, and collagen characteristics of beef strip loin steaks. Beef strip loins (n = 117) were selected from three quality grade treatments [Top Choice (Modest[superscript 00] – Moderate[superscript 100] marbling), Low Choice (Small[superscript 0] – Small[superscript 100] marbling), and Select (Slight[superscript 0] – Slight[superscript 100] marbling)] to equally represent three different marbling texture groups: fine, medium and coarse, via visual appraisal with the USDA marbling texture standards. Consumers (n = 104) rated all marbling texture groups similar (P > 0.05) for tenderness, juiciness, flavor, and overall liking, as well as rated a similar (P > 0.05) percentage of samples from each marbling texture group acceptable for each palatability trait. Moreover, consumers indicated no preference (P > 0.05) among marbling texture groups for visual desirability or likelihood to purchase. There were no differences (P > 0.05) among marbling texture treatments for Warner-Bratzler shear force, slice shear force, and pressed juice percentage. However, trained sensory panelists rated coarse marbled steaks higher (P < 0.05) than fine or medium marbled steaks for both beef flavor intensity and sustained juiciness as well as higher (P < 0.05) for initial juiciness than medium textured steaks. This minimal impact on palatability was further supported through evaluation of muscle histology and collagen traits. Marbling texture did not affect collagen characteristics, as coarse marbled steaks were similar (P > 0.05) to both fine and medium marbled steaks for soluble collagen, insoluble collagen, and total collagen content. Furthermore, all marbling texture groups (fine, medium, and coarse) performed similarly (P > 0.05) during the peak thermal transition phase of the perimysial fraction of collagen. However, marbling texture impacted (P < 0.05) adipocyte cross-sectional area, where coarse steaks had larger adipocytes in comparison to fine marbled steaks, but medium marbled steaks were similar (P > 0.05) to both coarse and fine marbled steaks. Similarly, quality grade affected adipocyte size, as Top Choice and Low Choice possessed larger (P < 0.05) adipocytes than Select steaks. However, marbling texture did not impact (P > 0.05) perimysial thickness. Additionally, marbling texture did not affect the percentage of myosin heavy chain (MHC) Type I fibers within each steak. However, medium marbled steaks possessed a greater (P < 0.05) percentage of MHC Type 2A fibers than both fine and coarse marbled steaks. The opposite trend was displayed in the percentage of MHC Type IIX fibers, as fine and coarse marbled steaks possessed more (P < 0.05) MHC Type IIX fibers in comparison to medium marbled steaks. There were no differences (P > 0.05) among quality grades for fiber type or marbling texture and quality grade for fiber cross-sectional area. Results from this study indicate marbling texture has minimal impact on eating quality and muscle histology; therefore coarse marbled carcasses should not be excluded from current and future branded beef programs.

Master of Science / Department of Animal Sciences and Industry / Christopher D. Reinhardt / Angus steers (n = 17,919) fed at a single feedlot in southwestern Kansas between 1997 and 2007 were used to evaluate the effects of various demographic and phenotypic characteristics (season of arrival, geographic origin, health status, rate of gain, quality grade, and yield grade) on feedlot health, performance, and carcass traits. Cattle were not commingled and were predominantly preconditioned and backgrounded prior to shipment to the feedlot. Season of arrival was categorized as winter (December, January, and February), spring (March, April, and May), summer (June, July, and August), or fall (September, October, and November). Regions were: SC = Texas, Oklahoma, and New Mexico; C = Colorado and Kansas; NC = Montana, Nebraska, and Wyoming; and SE = Georgia, Mississippi, South Carolina, Tennessee, Virginia, and West Virginia. Steers that originated in SC had the poorest ADG (P < 0.01) and those originating in C had the greatest ADG, HCW, and quality grade (P < 0.01). Steers that arrived during fall had the lowest ADG and those arriving during the summer had the greatest morbidity (P < 0.01). Morbidity decreased and performance increased with increasing initial BW; quality grade was only minimally related to arrival BW in steers which were not treated for disease. After accounting for yield grade differences, the association between morbidity and carcass quality and between quality grade and heavier final BW and HCW were diminished, although ungraded cattle had lower ADG, final BW, and HCW (P < 0.01). Increasing yield grade from 1 and 2 to yield grade 3 increased percentage Choice by 12.1 points (P < 0.01); there was no additional gain in quality grade moving to yield grade 4 and 5. More rapidly gaining steers were heavier and fatter at marketing; this translated to greater quality grade in all but steers with initial BW > 375 kg. Performance was very similar among cattle which graded Prime, Choice, and Select, suggesting that producers do not need to choose between performance and quality grade; instead, much of the difference in quality grade can be explained by differences in yield grade.

Master of Science / Food Science / John Unruh / A factorial arrangement of treatments was used to evaluate the effects of two subprimal types (chuck roll and knuckle), two quality grades (Premium Choice and Select), and three vacuum storage aging times before processing (7, 21, and 42 d) on ground beef patty display color stability and sensory attributes. At the end of each aging time, four knuckles or two chuck rolls representing their respective quality grade categories were combined and ground to form a sample batch. After a final grind, patties were formed using a patty machine, packaged in overwrapped trays, and displayed in a coffin-type retail case under continuous fluorescent lighting. Ground beef patties from chuck roll and Premium Choice subprimals had brighter red visual color scores, less discoloration, and higher (P<0.05) L*, a*, b*, and chroma values than those from knuckle and Select subprimals, respectfully. With increased display time, patties became (P<0.05) darker red and more discolored and had decreased L*, a*, b*, a/b ratio, and chroma values and increased hue angle values. Ground beef patties from Select knuckle subprimals had greater (P<0.05) oxygen consumption rate (OCR) than those from Premium Choice chuck roll, Select chuck roll and Premium Choice knuckle subprimals. Patties from subprimals aged 42 d had a lower metmyoglobin reducing ability (MRA) than those from subprimals aged 7 and 21 d. Greater aging and display times had higher (P<0.05) aerobic and lactic acid plate counts. In addition, thiobarbituric acid reactive substances values increased (P<0.05) from 7 to 21 d of aging and from 0 to 24 h of display. Ground beef patties from Premium Choice subprimals had a higher MUFA:SFA ratio (P<0.05) than those from Select subprimals. All treatments had acceptable sensory panel results with minimal differences due to treatment. Lower (P<0.05) peak force values for slice shear force and Lee-Kramer were recorded for patties from chuck roll, Premium Choice, and 42 d aged subprimals than those from knuckle, Select, and 7 d aged subprimals, respectfully. Overall, Premium Choice chuck rolls aged for fewer days would result in the most color stability and extended display life.

The objective of this project was to analyze the thermodynamics (thermal conductivity and diffusivity as well as protein denaturation) and physical properties (percent expressible moisture, cooking loss, change in steak thickness, shear force, texture profile analysis and rheological behavior) of beef steaks of different USDA quality grades (Upper 2/3 Choice and Select), thicknesses (thick and thin), and grill surface temperatures (high and low) 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, described by the tenderness and juiciness of cooked beef strip steaks. The elastic behavior of the surface and centers of beef steaks were analyzed to determine how the microstructure of the beef responded to applied stress. The elastic behavior of steak centers was influenced in a three-way interaction between USDA Quality Grade, steak thickness, and grill surface temperature while the elastic behavior of the surface of steaks was influenced only by USDA Quality Grade and steak thickness. These interactions along with the differences in the thermal characteristic of proteins suggest that the microstructure of beef steaks is significantly affected by each cooking treatment group. 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 cooking preparation should take into consideration that quality grade, thickness and cooking temperature will affect the textural eating qualities of beef steaks. Choice steaks were shown to be ideally sliced thick and cooked on a low grill surface temperature supported by the springiness, hardness, expressible moisture, and rheological data. Select steaks were not always effected by grill surface temperature and had similar results among the different measurements but the hardness, resilience and chewiness values along with viscosity suggest a thick steak cooked at a high grill surface temperature. Therefore, cooking parameters may be utilized as a mechanism to enhance beef steak palatability.

In an effort to increase beef demand, the beef industry has expanded beyond commodity beef merchandizing into value-added cuts. As these beef cuts are developed it is critical that the industry be able to characterize the flavor attributes of these products. A trained sensory panel is typically utilized to determine flavor characteristics of food products including beef. Prior to product evaluation, a product lexicon or dictionary of terms is developed in order to anchor and orient panelists to the various samples. Once the lexicon is developed, it can be used by a descriptive panel to evaluate samples. Currently, the beef industry does not have a full beef flavor lexicon with defined references; therefore a comprehensive sensory lexicon for describing the aroma and flavor of beef was developed by a 6-member panel at Kansas State University with extensive experience in lexicon development and descriptive analysis. Three descriptive panels utilized the beef flavor lexicon developed in Phase I by Kansas State University to evaluate the effect of USDA Quality Grade and cut on beef flavor and to validate the beef flavor lexicon to determine if it is ready for use by scientists. iv Results indicated that Choice steaks and roasts were higher in fat-like, and overall sweet flavor. Eye of round roasts were lowest in aroma and flavor attributes and bottom round roasts were highest in liver-like flavor. Flat iron steaks were highest in fat-like flavor compared to other cuts and top loin steaks tended to have the lowest intensity in flavor attributes compared to the steak cuts. The three sensory panels rated steaks and roasts similarly for aroma and flavor attributes and were generally less than 2- to 1-point different in rating intensities. The beef flavor lexicon was easily applied across the three institutions and should be ready to be used as a viable research and product development tool.

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The instrument grading assessments for the NBQA-2011 evaluated seasonal trends of beef carcass quality and yield attributes over the course of the year. One week of instrument grading data—HCW, gender, USDA QG, and YG factors—were collected every other month (n = 2,427,074 carcasses) over a 13-month period (November 2010 through November 2011) from four beef processing corporations, encompassing 17 federally inspected beef processing facilities, to create an overview of carcass quality and yield attributes and trends from carcasses representing approximately 8.5% of the U.S. fed steer and heifer population. Mean yield traits were: YG (2.86), HCW (371.3 kg), FT (1.19 cm.), and LM area (88.39 cm^2). The YG distribution was YG 1 (15.7%), YG 2 (41.0%), YG 3 (33.8%), YG 4 (8.5%), and YG 5 (0.9%). Distribution of HCW was <272.2 kg (1.6%), 272.2 kg to 453.6 kg (95.1%), ≥453.6 kg (3.3%). Monthly HCW means were: November 2010 (381.3 kg), January 2011 (375.9 kg), March 2011 (366.2 kg), May 2011 (357.9 kg), July 2011 (372.54 kg), September 2011 (376.1 kg), and November 2011 (373.5 kg). The mean FT for each month was November 2010 (1.30 cm), January 2011 (1.22 cm), March 2011 (1.17 cm), May 2011 (1.12 cm), July 2011 (1.19 cm), September 2011 (1.22 cm), and November 2011 (1.22 cm). The mean marbling score was Small49. USDA QG distribution was Prime (2.7%), Top Choice (22.9%), Commodity Choice (38.6%), and Select (31.5%). Interestingly, from November to May, seasonal decreases (P < 0.001) in HCW and FT were accompanied by increases (P < 0.001) in marbling. These data present the opportunity to further investigate the entire array of factors that determine the value of beef. Datasets utilizing the online collection of electronic data will likely be more commonly used when evaluating the U.S. fed steer and heifer population in future studies. These data indicate the wide array of carcasses produced by the beef cattle industry, and how the frequency of both YG and QG traits change from month-to-month.