Effect of Internal Nitrogen Cooling on Moisture Distribution in Cheddar Cheese Blocks Christopher Jackson Class of 2005.

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

Christopher Jackson

Class of 2005

Study Site

• Conducted research at the University of Minnesota’s Foods Science and Nutrition Department, St. Paul campus

• Researched under Dr. Lloyd Metzger, PhD

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

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

Previous Studies

• Reinold et al. found that “rapid [refrigerating]…of 640-lb blocks of…Cheddar 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.”

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

Hypotheses

1. 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

2. Internal cooling prior to refrigeration would cause moisture to migrate inwards then outwards, dispersing moisture evenly

Procedure

• Preparation of cheese:

– Used University of Minnesota’s stirred-curd Cheddar cheese-making protocol to make 2-lb and 20-lb cheese blocks

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

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

Procedure

• Determination of percent moisture:

– AOAC Method for Forced-Draft Ovens was used

– Moisture evaporated from solids

Results

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

• Average p = 0.00

Results

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

• Average p = 0.00

Results: linear equations for 4 Trials

• Equations for nitrogen-injected samples are positive and steep

• Equations for control samples are negative and not steep

Trial Linear equation for average % moisture in 5 layers of nitrogen

injected Cheddar cheese

Linear equation for average % moisture in 5 layers of control

Cheddar cheese

1 Y = 0.40x + 48.64 Y = -0.10x + 48.10

2 Y = 0.15x + 50.14 Y = -0.04x + 49.97

3 Y = 0.27x + 38.54 Y = -0.04x + 39.29

4 Y = 0.30x + 40.26 Y = -0.10x + 41.45

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

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

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

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

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

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

Christopher Jackson

Class of 2005