Department of Animal Science
Date of this Version
8-27-2011
Abstract
To evaluate processing methods for frozen beef subprimals, the effects of freezing and thawing rates on tenderness and sensory properties were evaluated. There were six treatments: fresh-never-frozen 14-day wet aged, fresh-never-frozen 21-day wet aged, blast frozen–fast thawed, blast frozen–slow thawed, conventionally frozen–fast thawed, and conventionally frozen–slow thawed (all frozen subprimals were aged for 14d prior to freezing). Three subprimal cuts - ribeye rolls (n = 90), strip loins (n = 90), and sirloins (n = 90) - were utilized with three replications of five samples per treatment per week (total of 9 weeks, N = 270). Blast freezing occurred by placing spacers between the boxes of meat on pallets at -28° C with high air velocity for 3 – 5 d until all the meat was frozen, and then the pallets were moved to a -28°C freezer for storage. Conventional freezing occurred with boxes of meat stacked on pallets and placed in a -28° C freezer with minimal air movement, the pallets were left in the freezer until shipping. Fast thawing of subprimals (to an internal temperature of -2° to 0° C) occurred by immersion in a circulating water bath (< 12° C) for 21 hrs, and slow thawing of subprimals occurred over a two week period by placing individual subprimals on tables at 0° C. Purge loss was measured after thawing. Steaks (2.5 cm thick) were cut from the longissimus thoracis (LT), longissimus lumborum (LL), and gluteus medius (GM) for Warner-Bratzler shear force (WBS) and trained sensory evaluation. Sensory samples were rated for tenderness, juiciness, connective tissue, and off-flavor after cooking to 71° C. Slow thawed subprimals had the greatest amount of purge loss (P < 0.001) in the LT, LL and GM. Fast thawed subprimals were equal or had less purge loss to fresh-never-frozen 14- and 21-d aged subprimals (P < 0.0001) in the LT, LL and GM. For LL and GM steaks, frozen treatments were equal or lower in WBS values to fresh-never-frozen 14- and 21-d aged steaks. For LL and LT steaks, slow thawed steaks we equal or lower in WBS when compared to fast thawed steaks (P = 0.01). No differences were detected in WBS among the GM steaks (P = 0.08). There were no differences in sensory tenderness within the LL, LT, and GM (P > 0.05). Juiciness in the LL and GM (P > 0.05) did not differ among treatments. The LT fresh-never-frozen 14- and 21-d aged product was juicier than the frozen product (P = 0.001). Differences were not detected in connective tissue in the LT or GM (P > 0.05). A greater amount of connective tissue was detected in the slow thawed LL compared to the fast thawed LL (P = 0.02). There were no differences in off-flavor in the LT and LL (P > 0.05). Conventionally frozen-fast thawed steaks had the strongest prevalence of off-flavor (P = 0.02) in the GM. Overall, freezing rate did not affect purge loss, and neither freezing nor thawing rates had significant meaningful effects on Warner-Bratzler shear force and sensory and were comparable to fresh-never-frozen subprimals.
Advisor: Chris R. Calkins
Comments
A THESIS Presented to the Faculty of The Graduate College at the University of Nebraska In Partial Fulfillment of Requirements For the Degree of Master of Science, Major: Animal Science, Under the Supervision of Professor Chris R. Calkins. Lincoln, NE: August 2011
Copyright 2011 Jerilyn E. Hergenreder