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Lecture 6 – Moisture Relationships. Lecture 6 – Moisture Relationships. Amount of moisture affects the following: Density: particle density decreases with increasing moisture content Force-deformation characteristics Thermal conductivity Heat capacity

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Lecture 6 – Moisture Relationships

BAE2023 Physical Properties of Biological Materials Lecture 5

slide2

Lecture 6 – 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 content

BAE2023 Physical Properties of Biological Materials Lecture 5

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Lecture 6 – 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

BAE2023 Physical Properties of Biological Materials Lecture 5

three concepts equilibrium mc water activity water potential

Lecture 6 – Moisture Relationships

Three concepts:

Equilibrium mc

Water activity

Water potential

BAE2023 Physical Properties of Biological Materials Lecture 5

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Lecture 6 – 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

BAE2023 Physical Properties of Biological Materials Lecture 5

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Lecture 6 – 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

BAE2023 Physical Properties of Biological Materials Lecture 5

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Lecture 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

BAE2023 Physical Properties of Biological Materials Lecture 5

equations wet basis dry basis

Lecture 6 – Moisture Relationships

Equations:

Wet basis

Dry basis

BAE2023 Physical Properties of Biological Materials Lecture 5

equations conversion wet to dry dry to wet

Lecture 6 – Moisture Relationships

Equations:

Conversion

Wet to dry

Dry to wet

BAE2023 Physical Properties of Biological Materials Lecture 5

wet basis example 700 kg of wheat contains 84 kg of water what is the mc w

Lecture 6 – Moisture Relationships

Wet basis example

700 kg of wheat contains 84 kg of water. What is the MCw ?

BAE2023 Physical Properties of Biological Materials Lecture 5

dry basis example 950 kg of oats contains 105 kg of water what is the mc d

Lecture 6 – Moisture Relationships

Dry basis example

950 kg of oats contains 105 kg of water. What is the MCd ?

BAE2023 Physical Properties of Biological Materials Lecture 5

conversion example convert the wheat and oat examples above

Lecture 6 – Moisture Relationships

Conversion example

Convert the wheat and oat examples above

BAE2023 Physical Properties of Biological Materials Lecture 5

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Lecture 5 – 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?

BAE2023 Physical Properties of Biological Materials Lecture 5

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Lecture 6 – Moisture Relationships

Another example

A 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?

BAE2023 Physical Properties of Biological Materials Lecture 5

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Lecture 6 – Moisture Relationships

Another example

An 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?

BAE2023 Physical Properties of Biological Materials Lecture 5

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Lecture 6 – Moisture Relationships

Another example

A 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?

BAE2023 Physical Properties of Biological Materials Lecture 5