Master of Science / Department of Animal Sciences and Industry / Travis G. O'Quinn / The objectives of this study were to determine the effect of enhancement on consumer and trained beef palatability scores of three quality grades when cooked to three degrees of doneness (DOD) and to determine the accuracy and repeatability of the Pressed Juice Percentage (PJP). Striploins of USDA Prime, Low Choice, and Low Select quality grades were used in this study. To maximize variation in juiciness, steaks were either enhanced (formulated for 108% pump with a solution of water, salt, and alkaline phosphates) or non-enhanced, and cooked to three degree of doneness (Rare: 60°C, Medium: 71°C, or Very Well-Done: 82°C). All samples were evaluated for Warner-Bratzler shear force (WBSF), Slice Shear Force (SSF), PJP, and palatability traits by consumer and trained panelists. Consumer panelists rated all enhanced treatments similar (P > 0.05) to each other and greater (P < 0.05) for juiciness, tenderness, flavor liking, and overall liking than all non-enhanced treatments. Consumer ratings of juiciness, tenderness, and overall liking scores increased (P < 0.05) as DOD decreased. Consumer panelists rated all enhanced treatments similar (P > 0.05) and greater (P < 0.05) for the percentage of steaks classified as premium quality. For trained panel initial juiciness, all enhanced treatments and non-enhanced Prime samples were similar (P > 0.05) and greater (P < 0.05) than other treatments cooked to Medium and Very Well Done. Results indicated PJP had a relatively high repeatability coefficient (0.70), indicating that only 30% of the variation observed was due to sample measurement differences. The PJP threshold values evaluated accurately segregated steaks by the probability of a sample being rated “juicy” by consumers, with the actual percentage of “juicy” samples determined to be 41.67%, 72.31%, 89.33%, and 98.08% for the <50%, 50 – 75%, 75 – 90%, and >90% categories, respectively. Therefore, enhancement has a substantial, positive effect on beef palatability. Enhancing higher quality beef does not provide an additional palatability benefit; hence the greatest economic advantage is in enhancing lower quality beef products. Results of this study indicate the PJP juiciness method is both repeatable and accurate at sorting steaks based on the likelihood of a steak being “juicy”.

Master of Science / Department of Animal Sciences and Industry / Travis G. O'Quinn / The objectives of this study were to evaluate the extent marbling compensates for reduced beef palatability at elevated degrees of doneness and to determine the relationship of residual moisture and fat in cooked steaks to beef palatability, specifically beef juiciness. Paired strip loins (IMPS # 180) were collected to equally represent five quality treatments [Prime, Top Choice (modest and moderate marbling), Low Choice, Select, and Select Enhanced (110% of raw weight)]. Steaks were grouped into sets of three consecutively cut steaks and randomly assigned a degree of doneness (DOD): very-rare (VR; 55°C), rare (R; 60°C), medium-rare (MR; 63°C), medium (M; 71°C), well-done (WD; 77°C), or very well-done (VWD; 82°C). Samples were subjected to consumer and trained sensory evaluation, Warner-Braztler shear force (WBSF), slice shear force (SSF), pressed juice percentage (PJP) evaluation, and raw and cooked proximate analysis. There were no (P > 0.05) interactions for consumer sensory ratings, indicating increased DOD had the same negative impact regardless of marbling level. There was a quality treatment × DOD interaction (P < 0.05) for percentage of steaks rated acceptable by consumers for juiciness. Increased marbling extended the point in which steaks became unacceptable for juiciness. Similarly, there was a quality treatment × DOD interaction (P < 0.05) for trained juiciness ratings. When cooked to MR and lower, Prime was only rated 8 to 18% higher (P < 0.05) than Select for trained juiciness ratings but was rated 38 to 123% higher (P < 0.05) than Select when cooked to M and higher. Besides cook loss, combined cooked moisture and fat percentage was more highly associated (P < 0.01) to consumer juiciness (r = 0.69) and trained initial (r = 0.84) and sustained (r = 0.85) juiciness ratings than all other objective evaluations. For regression analysis, cooked moisture and fat percentages, alone, were poor indicators of consumer and trained juiciness ratings. However, when combined, the regression equations explained 45, 74, and 69% of the variation in consumer, trained initial, and trained sustained juiciness ratings, respectively. These results indicate that increased marbling levels only offer “insurance” for juiciness of steaks that are cooked at high degrees of doneness, but not for other palatability traits. Additionally, cooked residual moisture and fat percentages when combined are a good indicator of sensory juiciness ratings.

The effect of oven temperature, dry-roasting,and breed on the eating quality of beef was determined by sensory and objective methods. Two adjacent standing rib and two adjacent chuck roasts of prime, choice, and good grades from animals of Hereford, Shorthorn, and Charolais breeding were dry-roasted. Control roasts (9-12th ribs) were cooked at 325 F. Experimental roasts (6-8th rib and two chucks) were assigned an oven temperature of 325 or 250 F at random. All roasts were allowed to reach ah internal temperature of 155 F as recorded on a potentiometer. Tenderness, as determined by a Warner-Bratzler shear, was greater in roasts cooked in the 325 F oven. The amount of press fluid and the percentage of total cooking loss due to drip was greater in the 325 F oven. The panel of judges preferred the flavor of meat which was dry roasted to that cooked by a moist heat method. An effect of breed on eating quality was shown: meat from animals of Charolais breeding rated highest by the taste panel for tenderness, juiciness, and flavor. One group of samples from a Shorthorn sire was consistently low in the three factors scored. There was a high correlation between objective and sensory methods of evaluation for tenderness and juiciness. Correlations were high between the taste panel scores for tenderness and flavor and also for juiciness and flavor. Flavor and backfat thickness were shown to be closely related.

Tenderness, juiciness, colour and flavour are the most important meat quality attributes affecting the consumer acceptance. Maintaining the consistency of meat products by avoiding variable quality has become a major concern and great challenge to the meat industry. This in turn will also benefit meat end-users in the marketplace by having more tender meat. The present study was designed to evaluate the overall effects of pre-rigor infusion with kiwifruit juice, which contains the plant protease, actinidin, on lamb quality. A total of 18 lambs (12 months old) were divided into three treatment groups (6 lambs per each treatment). After exsanguination, lamb carcasses were infused (10% body weight) with fresh kiwifruit juice (Ac), water (W) and compared with a noninfusion treatment which acted as a control (C). Samples from different muscle/cuts (longissimus dorsi (LD) vs leg chops) at different post-mortem times (1 day post-mortem vs. 3 wks vacuum packaged storage at 2°C) and display time (0 to 6 days after the post-mortem storage) were analysed to monitor the changes on meat physical properties (e.g., tenderness, temperature, drip and cooking loss, colour), biochemical changes (pH, proteins and lipids) and volatile flavour compounds after the infusion treatments. The most tender meat (lowest shear force values) (P < 0.001) detected in the Ac carcasses post-mortem compared with C and W carcasses demonstrated that kiwifruit juice was a very powerful meat tenderizer, and could contribute to the meat tenderization process efficiently and effectively. Compared with C and W carcasses, the enhanced proteolytic activity (P = 0.002) resulting from the actinidin in kiwifruit juice in Ac carcasses caused degradation of the myofibrillar proteins and the appearance of new peptides during postmortem ageing. A slight positive effect in a*-value (redness) and decreased lipid oxidation, found in leg chops, was thought to be caused by the natural antioxidants in kiwifruit juice. Kiwifruit juice infused into the meat did not alter (P > 0.05) the volatile flavour compound profile indicating that the meat from Ac treated carcasses maintained its natural lamb flavour. No treatment differences were found for the temperature decline (P > 0.05) between the infused treatments and C. The higher rate of pH decline (P < 0.05) found in W carcasses might have contributed to the higher drip and cooking loss. The unbound water in meat might contribute to the higher L*-values (lightness) found in W carcasses. In summary, the proteolytic tenderizing infusion treatment using kiwifruit juice is a feasible approach for the commercial meat industry to increase profits, and also could satisfy the eating quality standards required by the consumers. In addition, tenderizing meat by using kiwifruit juice could also provide the kiwifruit processors an additional option for use of their product to gain a more profitable return.