Tenderness classification of beef: IV. Effect of USDA quality grade on thepalatability of "tender" beef longissimus when cooked well done

The objective of this experiment was to determine the impact of USDA qualit y grade on the palatability of "tender" longissimus when cooked well done; Warner-Bratzler shear force was determined on longissimus thoracis steaks a ged 3 or 14 d postmortem (cooked to 70 degrees C) fi om carcasses of 692 st eers and heifers. Steaks from 31 carcasses with Modest or Moderate marbling scores (Top Choice) and steaks from 31 carcasses with Slight(00) to Slight (40) marbling scores (Low Select) were selected for this experiment from ca rcasses identified as "tender" (shear force < 5.0 kg at 3 d postmortem). Lo ngissimus thoracis steaks with 3 or 14 d of postmortem aging were cooked to 80 degrees C and evaluated by a trained sensory descriptive attribute pane l. Top Choice steaks had higher (P < .05) juiciness (5.8 vs 5.3) and beef f lavor intensity ratings (4.9 vs 4.6) than Low Select steaks. Aging of steak s for 14, rather than 3, d postmortem improved (P < .05) beef flavor intens ity rating (4.8 vs 4.7) but not (P > .05) juiciness rating (5.6 vs 5.5). Th e interaction (P < .05)of quality grade and aging time for tenderness ratin g indicated that Top Choice steaks were more tender (P < .05) with 3 d of a ging than steaks from Low Select carcasses (6.3 vs 5.8), but steaks from To p Choice and Low Select carcasses had similar(P > .05) tenderness ratings a fter 14 d of aging (7.0 and 6.8),Compared to palatability of steaks from Lo w Select carcasses, the palatability of steaks fi om Top Choice carcasses w as less affected by elevated degree of doneness in "tender" longissimus tho racis, especially when steaks were aged for only 3 d. Although differences in sensory traits between Top Choice and Low Select steaks were small, the consumers who cook beef well done may benefit from implementation of tender ness classification in conjunction with USDA quality grade.