Aberrations in postmortem tenderization of pork

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Aberrations in post-mortem tenderization of pork

• A.C. Dilger1, P. J. Rincker1, J. M. Eggert2,
• J. Killefer1, and F. K. McKeith1
• 1University of Illinois at Urbana-Champaign
• 2Monsanto Choice Genetics

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Introduction

• Improved meat tenderness with post-mortem storage
  at refrigeration temperatures has been documented
  since early 1900s
• Mechanism post-mortem proteolysis degrades
  structural proteins
• However, some pork loins do not conform to this
  pattern
• Increased storage does not increase tenderness

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Objective

• Determine the rate and extent of post-mortem
  tenderization in a group of pork loins
• Are there differences between sire lines?
• Can differences in aging patterns be attributed
  to other quality parameters?

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Methods

• 150 loins from a single kill day were transported
  to the University of Illinois Meat Science Lab
• Chops were collected from each loin as follows

Drip
10th rib
Randomized to aging times
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Methods

• Chops were randomized to aging times and aged at
  4C
• 2,7,14 and 21 d post-mortem
• After aging, chops were frozen and stored at
• -20C until analysis
• Chops were cooked to 70C, cored and sheared on
  texture analyzer
• To minimize variation, chops from one loin were
  all sheared on one day

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Methods

• Quality data was also collected from each loin at
  the tenth rib
• pH
• NPPC color, marbling and firmness
• Minolta L, a and b
• Drip loss
• Estimated purge and thaw loss from test chops
• Overall bone-in loin weight and cutting yield
• Statistical analysis with SAS including Proc GLM
  and Proc Corr

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Results
Entire population of loins
0.35 kg
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Results
n85
n35
n30
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Results
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Results
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Results
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Results
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Results
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Results

• Is change in shear force (tenderizing or
  toughening) predicted by quality differences?
• Change in shear force is not correlated to
• pH
• Color
• Marbling
• Firmness
• Minolta L, a, b
• Weights of cuts or loin

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Results

• Does toughening result from water loss?
• Change in shear force not correlated with drip
  loss
• Purge loss estimated with test chops
• Not correlated with purge loss
• Correlated with cooking loss (P lt 0.05)
• r0.40, R20.16
• Combination of water loss parameters does not
  improve explanation

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Conclusions

• Within a population of loins, there are
  differences in aging patterns
• Differ by genotype as well
• Majority of loins in population were of
  acceptable tenderness
• Changes in shear force not related to quality
  measures
• Weak relationship with cooking loss

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Future Directions

• Can differences in aging patterns be explained
  by
• Differences in the rate or extent of post-mortem
  proteolysis
• Differences in sarcomere length
• Differences in collagen content
• What is the underlying mechanism of toughening?
• Related to water loss

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Acknowledgements

• Monsanto Choice Genetics
• Dr. John Eggert
• Gail Ellis
• University of Illinois Meat Lab Crew
• Phil Rincker
• Questions?