moisture relationship
DESCRIPTION
about moisture in foodTRANSCRIPT
04/18/23 1
Moisture Relationships
– Amount of moisture affects the following:
• Density: particle density decreases with increasing moisture content
• Force-deformation characteristics• Thermal conductivity• Heat capacity• Electrical resistance: lower resistance
with higher moisture content04/18/23 2
Moisture Relationships
–Amount of moisture affects:• Fruits and veggies: 70-95% mc• Grains, seeds, dry food products: < 14%
• Meats: 60-80%• MC influences market value
04/18/23 3
Moisture Relationships
–Three concepts:• Equilibrium mc• Water activity• Water potential
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Moisture Relationships
– Equilibrium mc• Moisture transfers from product to
air during drying. • EMC describes the final moisture
reached during drying of lower moisture food products, grains, seeds
• Affects rate of drying• Explains mold growth in grain
04/18/23 5
Moisture Relationships
– Water Activity• Describes rate of deterioration
– Water Potential• Describes the effect of moisture
loss or gain on volume change and force deformation behavior of fruits and veggies
04/18/23 6
Moisture Relationships
– Determining Moisture Content (VERY IMPORTANT)
• Wet Basis–% of total weight with water
• Dry Basis –Ratio of water weight to dry matter weight
• One can be calculated using the other
04/18/23 7
Moisture Relationships
– Equations:
• Wet basis
• Dry basis
04/18/23 8
100 100water waterW
total water dry
W WM
W W W
100 waterdry
dry
WM
W
total dry wetW W W
Moisture Relationships
– Equations:• Conversion
– Wet to dry
– Dry to wet
04/18/23 9
100100
100100
wd
w
dw
d
MM
M
MM
M
Moisture Relationships
– Wet basis example700 kg of wheat contains 84 kg of water. What is the MCw ?
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Moisture Relationships
– Dry basis example950 kg of oats contains 105 kg of water.
What is the MCd ?
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Moisture Relationships
– Conversion exampleConvert the wheat and oat examples
above
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Moisture Relationships
– “How much water did we lose” example
750 kg of canola is dried from 17% MCw
to 12% MCw
How much water is removed during the drying process?
04/18/23 13
Moisture Relationships
– Another exampleA bin holds 2000 kg of wet grain
containing 500 kg of water. This grain is to be dried to a final MC of 14% (wb). What are the initial and final moisture contents of the grain (wb and db)?
How much water is removed during drying?
04/18/23 14
Moisture Relationships
– Another exampleAn elevator has 14,000 kg of wheat at
12% MCw and 25,000 kg of wheat at 17% MCw. The manager has a rule that all stored wheat must be below 15% MCw. If the wheat is mixed together, will it meet the storage criteria?
04/18/23 15
Moisture Relationships
–Another exampleA bag containing 1.5 kg of popcorn has been stored in the cabinet for a long time. When heated appropriately, only a few kernels popped. Testing showed that the MCw was 9%. Popcorn pops best at 13%. How much water should be added to bring it to this moisture?
04/18/23 16
Moisture Relationships