Master of Science / Department of Animal Sciences and Industry / Travis G. O'Quinn / The objective of this study was to evaluate the impact of quality grade on beef eating quality of top sirloin steaks when cooked to multiple degrees of doneness (DOD). Beef top sirloin butts (N = 60; 15 / quality grade) were collected to equally represent 4 quality grades [Prime, Top Choice (modest00 – moderate100), Low Choice, and Select]. Top butts were cut into six consecutive steaks, and then divided laterally to get a total of twelve steaks per top butt. Steaks were assigned to one of three DOD: rare (60°C), medium (71°C), and well-done (77°C). Steaks within DOD were assigned to consumer sensory analysis, trained sensory analysis, fat and moisture analysis, and Warner-Bratzler shear force (WBSF). There were no interactions (P > 0.05) for all consumer ratings of palatability traits, indicating increases in DOD had the same impact across all quality grades. There was a difference (P > 0.05) within quality grade for consumer ratings of juiciness (P > 0.05). Prime steaks had greater (P < 0.05) juiciness ratings than all other quality grades, except for Top Choice. As DOD increased, consumer ratings and the percentage of steaks rated acceptable for each palatability trait decreased (P < 0.05; rare > medium > well-done). There was a quality grade × DOD interaction (P < 0.05) for trained sensory panel juiciness scores. When cooked to medium, Prime and Top Choice steaks were rated higher (P < 0.05) for juiciness than Low Choice and Select steaks. Similar to consumer ratings, trained panel ratings of tenderness decreased (P < 0.05) as DOD increased (rare > medium > well-done). Lastly, there were no quality grade by DOD interactions (P > 0.05) for Warner-Bratzler shear force. These results indicate that regardless of the DOD steaks were cooked to, quality grade had minimal impact on the palatability of beef top sirloin steaks. Therefore, unless cooked to a medium DOD, it is unnecessary for consumers, retailers, and foodservice to pay premium prices for higher quality top sirloin steaks, as the same eating experience will be given.

FundaÃÃo de Amparo à Pesquisa do Estado do Cearà / Objetivou-se com o presente estudo avaliar a utilizaÃÃo da ultrassonografia e qualidade de carne de cordeiros Santa InÃs de diferentes classes sexuais submetidos à restriÃÃo alimentar. Foram utilizados 30 cordeiros, 15 castrados e 15 nÃo castrados, com aproximadamente dois meses de idade e peso corporal inicial mÃdio de 13,00  1,49 kg. Os cordeiros foram distribuÃdos em delineamento inteiramente casualizado em arranjo fatorial 3x2 (nÃvel de restriÃÃo x classe sexual), de acordo com a quantidade de alimento fornecida. A duraÃÃo do experimento foi determinada pelo tempo necessÃrio para que a mÃdia de peso corporal dos animais de um dos tratamentos atingisse 28 kg, ocasiÃo em que todos os 30 animais foram abatidos. NÃo houve interaÃÃo significativa entre os nÃveis de restriÃÃo e a classe sexual para Ãrea de olho de lombo (AOL), espessura de gordura subcutÃnea (EGS), profundidade do Longissimus dorsi na lombar (PLDL) e espessura de gordura subcutÃnea na lombar (EGSL) no momento do abate. Possivelmente, devido à reduÃÃo na oferta do alimento, a AOL, a EGS, a PLDL e a EGSL apresentaram valores mÃdios reduzidos em funÃÃo do aumento no nÃvel de restriÃÃo alimentar. Houve interaÃÃo entre os nÃveis de restriÃÃo alimentar e as datas de mensuraÃÃo para AOL, EGS, PLDL e EGSL. Foram observadas correlaÃÃes significativas entre as caracterÃsticas in vivo e as caracterÃsticas de carcaÃa. A AOL por ultrassonografia in vivo foi altamente correlacionada com a medida desta variÃvel na carcaÃa, demonstrando a eficiÃncia do mÃtodo. Houve interaÃÃo entre os nÃveis de restriÃÃo alimentar e as classes sexuais para as variÃveis intensidade de amarelo e pH no mÃsculo Longissimus lumborum e para forÃa de cisalhamento no mÃsculo Semimembranosus. Para os animais nÃo castrados, a intensidade de amarelo foi maior para o nÃvel de 30% de restriÃÃo no mÃsculo Longissimus lumborum. NÃo houve interaÃÃo significativa entre os nÃveis de restriÃÃo e a classe sexual para os aspectos de qualidade relacionados à saturaÃÃo de cor, tonalidade da cor, luminosidade, intensidade de vermelho, capacidade de retenÃÃo de Ãgua e perda de peso por cocÃÃo para os mÃsculos Longissimus lumborum e Semimembranosus. Cordeiros Santa InÃs submetidos à restriÃÃo alimentar apresentam menores valores para AOL, EGS, PLDL e EGSL, sendo estas avaliadas in vivo. Embora a restriÃÃo alimentar e a classe sexual tenham influenciado as variÃveis relacionadas à qualidade da carne dos animais avaliados, os valores mÃdios observados sÃo considerados aceitÃveis pela literatura. Os nÃveis de restriÃÃo alimentar e a classe sexual influenciaram algumas caracterÃsticas importantes da qualidade da carne de cordeiros Santa InÃs. / The objective of the present study to evaluate the use of ultrasound and quality lamb meat Santa InÃs of different sex class subjected to food restriction. Were used thirty Santa InÃs lambs, 15 castrated and 15 nonâcastrated, with approximately two months of age and initial body weight in average of 13  1.49 kg. The lambs were assigned to a completely randomized design in a 3x2 factorial arrangement (levels of feed restriction x sex class), according to the amount of food provided. Experiment period was determined based in the time required for the animals one of the groups achieved 28 kg of body weight in average, when all 30 animals were slaughtered. There was no significant interaction between restriction levels and sexual class to rib eye area (REA), subcutaneous fat thickness (SFT), depth of Longissimus dorsi in the lumbar (DLDL) and thickness of subcutaneous fat in the lumbar (TSFL) at slaughter. Possibly due reduction in food supply, the REA, the SFT, the DLDL and The TSFL showed average values reduced in function increase levels of feed restriction. There was interaction between levels of feed restriction and the measurement dates to REA, SFT, DLDL and TSFL. Significant correlations were observed between the in vivo characteristics and carcass characteristics. The REA by ultrasound in vivo was highly correlated with the measure of this variable in the carcass, demonstrating its efficacy. There was interaction between levels of feed restriction and sex classs for the variables intensity of yellow and pH in Longissimus lumborum and shear force in Semimembranosus muscle. To animals non-castrated, the intensity of yellow was higher with 30% restriction on the Longissimus lumborum. There was no significant interaction between restriction levels and sexual class to quality aspects related to color saturation, color tone, luminosity, red intensity, water retention capacity and weight loss for cooking for Longissimus lumborum and Semimembranosus muscles. Santa Ines lambs subjected to food restriction have lower values for REA, SFT, DLDL and TSFL, which are valued in vivo. Although feed restriction and sexual class have influenced the variables related to the meat quality of animals evaluated, the mean values observed are considered acceptable in the literature. The food restriction levels and sexual class influenced some important features of meat quality Santa Ines lamb.