Factors Affecting Myoglobin Color Reversion in Cooked Ground Beef Patties

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Factors Affecting Myoglobin Color Reversion in
Cooked Ground Beef Patties

• Kurt Vogel and Jim Claus
• University of Wisconsin-Madison
• Meat Science and Muscle Biology Laboratory

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Color Reversion
Introduction

• Reappearance of a red color some time after
  cutting open a cooked ground beef patty.

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Background

• Limited information on color reversion
• Metmyoglobin (MMb) can be reduced to oxymyoglobin
  (OMb) and deoxymyoglobin (DMb) in beef extracts
  (Osborn et al. 2003)
• High pH protects myoglobin from denaturation
  (Trout, 1989)
• Color reversion occurred in cooked pork roasts
  (Ghorpade and Cornforth, 1993)

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What do we know?

• Color reversion is contingent on pH, reducing
  ability, and endpoint temperature
• Two reactions can induce brown, fully-cooked
  color
• Metmyoglobin formation
• Hemichrome formation
• Color Reversion can occur!

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Objectives

• Establish the endpoint cooking temperature
  necessary to produce a fully cooked color that
  turns red when the patty is removed from the heat
  source and cut.
• Determine the effect of beef age on color
  reversion.
• Evaluate the effect of storage state (fresh
  versus frozen) on color reversion.

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Materials and Methods
Raw Materials

• Received five- 11 kg samples of beef trimmings
  from 2 commercial meat processors
• 7 to 10 d postmortem
• 92.5 lean
• pH 5.66 to 6.14
• Immediately ground (1.9 cm plate), blended,
  vacuum packaged, and stored at 0-2 C for three
  days

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Sample Preparation

• 1.5 kg retained for each of the three treatments
• Trt 1 Cooked immediately (not aged)
• Trt 2 Cooked after 7 day aged at 0-2 C in PVC
  film
• Trt 3 Cooked after frozen storage for 60 days
  in vacuum bag
• Reground twice before patty formation
• Three 113.5 g patties per treatment- manual patty
  press

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Cooking

• Cooking rate 6.18 C per minute
• On liquified propane (lp) gas grill
• Grill Temp 316 C
• Turned once at 43.3 C
• Removed at 62.8 C and foil wrapped
• Temperature increased to 69.4 C

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Color Sampling

• Patties cooled to 54.4 C at room temp
• Longitudinally cut with electric fillet knife
• Color measurements- at 0 and 10 min post-cut
• Minolta colorimeter readings (n3)
• CIE L a b
• Shimadzu UV-VIS spectrophotometer reading (n1)
• DMb (R474 nm/ R525 nm)
• OMb (R610 nm/ R525 nm)
• MMb (R572 nm/ R525 nm)

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Results and Discussion
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a Age and Time Effect
Plt0.05 for Age Plt0.001 for Time
Time post-cut
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Hue Angle Age and Time Effect
plt0.01 for Time
Hue Angle
Time post-cut
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Chroma Age and Time Effect
plt0.05 for Age plt0.0001 for Time
Chroma
Time post-cook
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a Storage State and Time Effect
p.0001 for Storage Plt.005 for Time
a
Time post-cook
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Hue Angle Storage State and Time Effect
plt0.01 for Storage
Hue Angle
Time post-cook
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Chroma Storage State and Time Effect
plt0.0001 for Age plt0.0001 for Time
Chroma
Time post-cook
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Conclusions

• Color reversion can occur in cooked ground beef
  patties
• Fresh and frozen beef can undergo color reversion
• Beef age can reduce magnitude of color reversion
• Color reversion does not represent a food safety
  risk, but a palatability risk!
• The most reliable measure of proper end-point
  temperature is through the use of a thermometer