Animal Science Department

 

Date of this Version

8-27-2011

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

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

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