Effect of Internal Nitrogen Cooling on Moisture Distribution in Cheddar Cheese Blocks

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Effect of Internal Nitrogen Cooling on Moisture
Distribution in Cheddar Cheese Blocks

• Christopher Jackson
• Class of 2005

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Study Site

• Conducted research at the University of
  Minnesotas Foods Science and Nutrition
  Department, St. Paul campus
• Researched under Dr. Lloyd Metzger, PhD

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Definition of Stirred-Curd Cheddar Cheese

• Cheddaring cheese consists of piling and
  re-piling blocks of warm cheese in a vat to
  increase lactic acid production and kill bacteria
• Used now for flavor and texture

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Goals

• To test the effects of internal nitrogen cooling
  on moisture distribution in Cheddar cheese
• To achieve more even moisture distribution with
  internal nitrogen cooling and refrigeration than
  with the conventional method of refrigerating
  cheese

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Previous Studies

• Reinold et al. found that rapid
  refrigeratingof 640-lb blocks ofCheddar
  cheese produced uneven moisture distribution.
• Moisture in cheese migrates from warmer to cooler
  regions
• According to D. M. Barbano, The most desirable
  situation would be uniform and rapid cooling of
  all positions within a cheese block.

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Relevance to the Cheesemaking Industry

• Percent moisture in cheese directly affects the
  texture and, inherently, the quality of cheese
• Even moisture distribution increases the quality
  of cheese
• Some portions of conventionally cooled cheese may
  be inappropriate to sell as Cheddar cheese
• More even moisture distribution makes all
  portions of the cheese block appropriate to sell

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Hypotheses

• Injecting nitrogen into the center of the cheese
  block prior to refrigeration would cause moisture
  in cheese to be distributed more evenly than the
  conventional method of refrigerating cheese
  blocks
• Internal cooling prior to refrigeration would
  cause moisture to migrate inwards then outwards,
  dispersing moisture evenly

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Procedure

• Preparation of cheese
• Used University of Minnesotas stirred-curd
  Cheddar cheese-making protocol to make 2-lb and
  20-lb cheese blocks

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Procedure

• Nitrogen Injection
• Blocks were cut into 14 cm x 14 cm x 6 cm blocks
• Nitrogen was injected into half of the blocks
  until excess nitrogen is ejected

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Procedure

• Preparation of cheese
• 5 layers of cheese were cut from one block
• Ground in blender to particle size 2-5 mm
• Weighed in aluminum dishes

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Procedure

• Determination of percent moisture
• AOAC Method for Forced-Draft Ovens was used
• Moisture evaporated from solids

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Results

• Layer 5 in all four trials shows
  nitrogen-injected samples have significantly
  higher moisture than control samples
• Average p 0.00

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Results

• Layer 1 in trials 3 and 4 show control samples
  have significantly higher moisture than
  nitrogen-injected samples
• Average p 0.00

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Results linear equations for 4 Trials

• Equations for nitrogen-injected samples are
  positive and steep
• Equations for control samples are negative and
  not steep

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Discussion 1st Hypothesis

• Injecting nitrogen into the center of the cheese
  block prior to refrigeration would cause moisture
  in cheese to be distributed more evenly than the
  conventional cooling method
• Hypothesis rejected nitrogen injection prior to
  refrigeration did not create more even moisture
  distribution than refrigeration

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Discussion 2nd Hypothesis

• Internal cooling prior to refrigeration would
  cause moisture to migrate inwards then outwards,
  dispersing moisture evenly.
• First half of hypothesis supported nitrogen
  injection caused moisture to migrate inwards
• Second half rejected refrigeration after
  injection did not cause moisture to migrate
  toward surface of cheese blocks
• Nitrogen injection too profound

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Further Study

• To test the effect of different amounts of
  nitrogen on moisture distribution in cheese
  blocks
• To test the effect of different refrigeration
  temperatures after nitrogen-injection on moisture
  distribution in cheese blocks

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Why Further Research is Important

• If injecting nitrogen prior to refrigeration can
  be show to cause more even moisture distribution,
  then
• Cheese blocks have more consistent percent
  moisture
• More consistent cheese quality
• Ability to sell all portions of cheese as Cheddar
  cheese

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Acknowledgements

• Dr. Lloyd Metzger, Ph. D.
• For his guidance
• Mrs. Lois Fruen
• For the opportunity to join the Breck Research
  Team and advice on all aspects of my research
• Peggy Sue Lethola, Rohit Kapoor, Ray Miller, Jodi
  Nelson, Adrian Pollard, and Praveen Upreti
• For teaching me the art and science of
  cheese-making and sharing your research with me
• Team Research
• For the support and friendship

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Effect of Internal Nitrogen Cooling on Moisture
Distribution in Cheddar Cheese Blocks

• Christopher Jackson
• Class of 2005