Animal Science Department

 

Date of this Version

November 2006

Comments

A DISSERTATION Presented to the Faculty of The Graduate College at the University of Nebraska In Partial Fulfillment of Requirements For the Degree of Doctor of Philosophy. Major: Animal Science. Under the Supervision of Professor Chris R. Calkins. Lincoln, Nebraska, December, 2006. Copyright 2006 Jennie Marie James Hodgen.

Abstract

Projects were conducted to increase knowledge of liver-like off-flavor origins in muscles from the beef chuck and round. Effects of cooking rate and holding time on off-flavor of various steaks from ten carcasses were determined. Off-flavor from these muscles was lowest when the steaks were cooked slowly (on a 149°C grill versus a 249°C grill) and when held for one hour prior to evaluation. The M. infraspinatus had the least off-flavor, and the M. vastus intermedius had the most intense off-flavor. These data suggest a carcass with one off-flavored muscle is likely to have other off-flavored muscles in the chuck and round. It appears the off-flavors are aromatic volatiles as off-flavored samples could be differentiated during cooking. Investigations to identify compounds causing beef off-flavors were undertaken. A protocol was developed to capture volatile compounds from raw, pulverized meat samples in a polymer column and elute the volatiles with ethyl ether for injection into a gas chromatograph (GC). Differences in peak height/area could be seen between samples identified as normal and liver-like in flavor. Compound identification using the ether sample was implausible with GC-mass spectrometry (GCMS) so samples were run in a purge and trap GCMS system (PT). Compound differences in normal and liver-like samples were those associated with lipid oxidation; β-pinene, 1-octen-3-ol, and 2,4-decadienal were higher in concentration in liver-like off-flavored samples in four muscles tested, as well as in raw liver. Solid phase microextraction (SPME) with GCMS validation identified the presence of similar compounds identified with PT in addition to differences in lower molecular weight compounds in liver-like samples not detectable in the previous study. Lipid oxidation compounds are at least partially responsible for liver-like off-flavor, and different muscles have their own unique volatile profile. Twenty-eight compounds were found in all four raw normal flavored muscles. M. triceps brachii had the fewest compounds, while M. rectus femoris had the most compounds with ten unique from those in other muscles.
Advisor: Chris R. Calkins

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