USDA Quality Grade and Degree of Doneness Effects on Nutrient Content of Beef Top Loin Steaks

摘要

To determine how the nutrient content of steaks from different USDA quality grades were affected when cooked to different degrees of doneness, ten steaks were obtained from each of five Prime, five Choice, and five Select strip loins and assigned to one of five degree of doneness treatments (two sets of treatments per strip loin): raw (uncooked), medium rare (63°C), medium (71°C), well done (77°C), and very well done (82°C). Steaks were dissected into separable tissue components: lean, fat, and refuse. Lean tissue was used to obtain proximate analyses of protein, moisture, fat, and ash. With increasing degree of doneness, cooking yield and percent moisture decreased, whereas percent fat and protein increased (all P < 0.05). Grade did not (P > 0.05) influence percentage separable lean. Select steaks had (P < 0.05) less fat and more separable refuse than Choice and Prime steaks. As degree of doneness increased, percent separable lean decreased slightly, but only very well done steaks had (P < 0.05) less separable lean. With increasing grade, caloric value increased: there was a 46.1% increase in caloric values between Select and Prime steaks. There was a 9.0% increase in caloric values between medium rare and very well done steaks: for every increase in a degree of doneness, there was ～18 kJ increase in a 100 g edible portion. Degree of doneness and USDA quality grade impacted cooking yields, proximate composition, and caloric values of top loin steaks.