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Understanding Moisture Content Variations in Biological Materials

Learn about measuring moisture content in biological materials, sampling methods, oven drying, and various techniques such as distillation and spectroscopy. Understand equilibrium moisture content and predictive equations for EMC. Example problems included.

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Understanding Moisture Content Variations in Biological Materials

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  1. Lecture 7 – Moisture Relationships Announcements BAE2023 Physical Properties of Biological Materials Lecture 6 Moisture Relationships

  2. Lecture 7 – Moisture Relationships 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 BAE2023 Physical Properties of Biological Materials Lecture 6 Moisture Relationships

  3. Lecture 7 – Moisture Relationships 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 BAE2023 Physical Properties of Biological Materials Lecture 6 Moisture Relationships

  4. Lecture 7 – Moisture Relationships 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) BAE2023 Physical Properties of Biological Materials Lecture 6 Moisture Relationships

  5. Lecture 7 – Moisture Relationships Chemical method Karl Fischer method: page 84 Electrical method Moisture meters Grain capacitance/conductance meter BAE2023 Physical Properties of Biological Materials Lecture 6 Moisture Relationships

  6. Lecture 7 – Moisture Relationships 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 BAE2023 Physical Properties of Biological Materials Lecture 6 Moisture Relationships

  7. Moisture RelationshipsChpt 3, Pages 81-105 BAE2023 Physical Properties of Biological Materials Lecture 6 Moisture Relationships

  8. Moisture RelationshipsChpt 3, Pages 81-105 BAE2023 Physical Properties of Biological Materials Lecture 6 Moisture Relationships

  9. Lecture 7 – Moisture Relationships BAE2023 Physical Properties of Biological Materials Lecture 6 Moisture Relationships

  10. Lecture 7 – Moisture Relationships 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 BAE2023 Physical Properties of Biological Materials Lecture 6 Moisture Relationships

  11. Lecture 7 – Moisture Relationships Modified Henderson: Chung-Pfost: K, N, and C are constants specific to materials (Table 3.2, pg 92) BAE2023 Physical Properties of Biological Materials Lecture 6 Moisture Relationships

  12. Lecture 7 – Moisture Relationships Modified Henderson: Chung-Pfost: A, B, E, F, K, N, and C are constants specific to materials (Table 3.2, pg 92) BAE2023 Physical Properties of Biological Materials Lecture 6 Moisture Relationships

  13. Lecture 7 – Moisture Relationships 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: BAE2023 Physical Properties of Biological Materials Lecture 6 Moisture Relationships

  14. Lecture 7 – Moisture Relationships Example: Using the Modified Henderson and the Chung-Pfost Equations: Determine the moisture content of rough rice at 20°C and 35% RH BAE2023 Physical Properties of Biological Materials Lecture 6 Moisture Relationships

  15. Lecture 7 – Moisture Relationships 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? BAE2023 Physical Properties of Biological Materials Lecture 6 Moisture Relationships

  16. Lecture 7 – Moisture Relationships 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. BAE2023 Physical Properties of Biological Materials Lecture 6 Moisture Relationships

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