The effects of carcass maturity and early-postmortem aging on the pyridinoline concentration and thermal stability of bovine intramuscular collagen

Steven Hultz Smith, Purdue University

Abstract

The initial study involved the development of an analytical procedure using high-performance liquid chromatography and the 9-fluorenylmethyl chloroformate-1-aminoadamantane (FMOC-ADAM) amino acid fluorescence-tagging technique for the determination of hydroxyproline (HYP) in very small muscle samples. A 7.5 min elution program was developed wherein HYP was completely resolved in three min. An alternate program was established for the additional determination of proline wherein it eluted after six min with a total run time of 10 min. This procedure was proven to provide results similar (P =.12) to those of a standard colorimetric assay. In a second study, 49 Holstein beef animals, representing all USDA maturity groups, were utilized to determine the effect of carcass maturity on the content of pyridinoline, a mature collagen crosslink, in bovine intramuscular collagen (IMC) as well as the relationship of pyridinoline to thermal stability of IMC. As carcass maturity increased, heat-labile collagen solubility (% Sol) and thermal shrinkage temperature (T$\sb{\rm s}$) increased (P $<$.01) but enthalpy (H$\sb{\rm s}$) remained unchanged (P $>$.05). Pyridinoline concentration increased (P $<$.01) linearly with maturity indicating that this crosslink is involved in maturity-induced stabilization of IMC. Strong relationships between pyridinoline content and maturity (r =.56, P $<$.001) and between the former and T$\sb{\rm s}$ (r =.34, P $<$.05) support this stabilization role. The relationship between pyridinoline and T$\sb{\rm s}$ also indicates that T$\sb{\rm s}$ is a useful means of evaluating IMC crosslinking. In the final study, the effect of early-postmortem aging at three temperatures (1, 19 and 37$\sp\circ$C) on the thermal stability and crosslinking (pyridinoline) characteristics of bovine IMC was assessed. Semimembranosus muscle strips were removed from six A maturity steers while in a restraint mechanism and placed in heavy mineral oil equilibrated at test temperatures. Samples were taken from each strip at 0, 1, 2, 4, 6 and 8 h postmortem. Neither temperature nor aging time had an effect (P $>$.05) on pyridinoline content and enthalpy. %Sol tended (P $>$.05) to increase with increasing temperature, whereas there was a curvilinear increase (P $<$.05) with aging time. A significant time x temperature interaction was demonstrated for T$\sb{\rm s}$, wherein the T$\sb{\rm s}$ decrease was greater (P $<$.05) with aging at 37 C than at 1 and 19$\sp\circ$C. The T$\sb{\rm s}$ of IMC was similar for the 1 and 19$\sp\circ$C treatments for the first 6 h of aging. At 8 h postmortem, the decline in T$\sb{\rm s}$ was greater at 19$\sp\circ$C than at 1$\sp\circ$C. It was concluded that pyridinoline does not appear to be involved in the postmortem aging modification of IMC. The data suggest the possibility of muscle contraction state having imposed a modifying effect on T$\sb{\rm s}$ of IMC.

Degree

Ph.D.

Advisors

Judge, Purdue University.

Subject Area

Food science

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