9/23/2015bae2023 physical properties of biological materials lecture 6 moisture relationships 1...

04/19/23 BAE2023 Physical Properties of Biological Materials Lecture 6

Moisture Relationships

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Announcements

Lecture 7 – Moisture Relationships



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–Measuring moisture content•Oven drying…most common•Distillation, chemical reactions, electrical resistance or capacitance, near infrared spectroscopy, nuclear magnetic resonance•Variation due to how water is bound…chemically or physically




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–Sampling•Grain probe or trier (trucks or barges)

•Diverter sampler (streams of material)

•Ellis cup (material on a belt)

•Samples divided by a Boerner divider…100-200g samples




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–Convection Oven Method•ASAE Standard S352.1, grain and seeds

–Numbered dishes are heated for 1 hour–Grain is placed in dishes and in oven–Removed and placed in desiccator to be brought to room temperature and weighed–Heating times and temp vary by material–Wheat, oats, rye…130°C, 19 hr, 22hr, or 16 hr respectively (just an example)




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–Chemical method•Karl Fischer method: page 84

–Electrical method•Moisture meters

•Grain capacitance/conductance meter




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–Equilibrium Moisture Content (EMC)•Material moisture content when equilibrium occurs during the exchange of moisture between material and air

–Equilibrium Relative Humidity•RH of air when equilibrium occurs

–Relationship varies with temperature




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Moisture RelationshipsChpt 3, Pages 81-105



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Moisture RelationshipsChpt 3, Pages 81-105



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Equivalent Relative

Humidity, %

(40% seed oil content)

Temperature, °F

20 30 40 50 60 70 80

20 4.9 4.5 4.1 3.8 3.6 3.4 3.2

30 6.5 5.9 5.5 5.1 4.8 4.5 4.3

40 8.1 7.4 6.8 6.3 6.0 5.6 5.3

50 9.6 8.8 8.1 7.6 7.1 6.8 6.4

60 11.3 10.3 9.6 9.0 8.4 8.0 7.6

70 13.1 12.1 11.2 10.5 10.0 9.3 8.9

80 15.4 14.2 13.2 12.3 11.6 11.0 10.5

90 18.6 17.2 16.0 15.0 14.2 13.5 12.8




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•Two equations for predicting EMC–Henderson or modified Henderson Equation–Chung-Pfost equation

•Each has 2 forms:–EMC as a function of temperature and MCd

–MCd as a function of rel. humidity and temperature




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–Modified Henderson:

–Chung-Pfost:

•K, N, and C are constants specific to materials (Table 3.2, pg 92)




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–Modified Henderson:

–Chung-Pfost:

•A, B, E, F, K, N, and C are constants specific to materials (Table 3.2, pg 92)




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–When all you know is the % dry matter as fat and % dry matter as nitrogen free extract (% carb which does not include fiber), use this equation from Vemuganti and Pfost:




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–Example:•Using the Modified Henderson and the Chung-Pfost Equations:

–Determine the moisture content of rough rice at 20°C and 35% RH




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–Example:•Using the Modified Henderson and the Chung-Pfost Equations:

–If the air temperature is 22°C, what does the rh need to be to dry corn to 15% MCw?




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–Example:•Compute the final moisture content after thoroughly mixing 60 kg of 18% MC corn with 40 kg of 12% MC corn.

•Compute the final moisture content after mixing 30 kg of 18% MC corn with 40 kg of 12% MC Corn.


9/23/2015bae2023 physical properties of biological materials lecture 6 moisture relationships 1...

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