Lesson Unit One Physical Properties of Biological Materials

Lesson Unit One Physical Properties of Biological Materials Prof. DAN Dharmasena Professor in Postharvest Engineering & Technology Dept. of Agric. Engineering 1/10/2022 DAN Dharmasena 1

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One Physical property at a glance 1/10/2022 3

PHYSICAL PROPERTIES OF AGRICULTURAL PRODUCTS References: 1. Nuri N. Mohsenin, Physical Properties of Plant and Animal Materials (1986) Gordon and Breach Science publishers, New York. 2. Nuri N. Mohsenin, 1980. Thermal properties of foods and agricultural materials 3. P. H. Pandey, Principles and Practices of Postharvest Technology, Third edition (2002) Kalyani Publishers. ISBN 81 -7096 -632 -9 1/10/2022 DAN Dharmasena 4

1. 0 Introduction Agricultural produce (plant and animal material) is subjected to various handling and processing practices. Ie. Mechanical handling, Thermal processing, Optical testing, Electromagnetic testing (Microwave & IR heating) Washing and handling in water etc. Applications are ever increasing. 5 1/10/2022 DAN Dharmasena

Little is known about basic physical characteristics and other properties: • Specific heat and othermal characteristics • Electrical conductivity • Dielectric constants (parameter on reaction to electromagnetic waves) • Light transmittance characteristics • Mechanical properties: stress-strain behaviour Resistance to compression, Impact & Shear Coefficient of friction etc. 1/10/2022 DAN Dharmasena 6

Exposure to electro magnetic radiation Incident ray Air (ε’ =1) Reflected rays (40 <ε’<70) Food Transmitted rays ε’ =dielectric constant/permittivity 1/10/2022 DAN Dharmasena Air (ε’ =1) 7

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What is the importance? Information of physical properties is essential in 1. Design of new machines, structures, processes and controls 2. For the determination of machine or operation efficiency 3. Developing new consumer products of plant or animal origin 4. In quality evaluation for final product consistency 1/10/2022 D A N Dharmasena 9

Who needs this information? • Agric/Food. Engineers • Food scientists • Food processors • Plant and animal breeders/Biotechnologists 1/10/2022 D A N Dharmasena 10

Corn in the field Physical properties to predict harvest maturity Harvesting As Livestock Forage Resistance to cutting, chopping, Shredding Aerodynamic properties: Blowing, conveying Compaction and load distribution in silo (for Loading, storage and unloading As Grain Resistance to detachment from the cob, Aerodynamic properties: in cleaning Electrical, Optical properties: MC determination Thermal Prop: Drying, Heat treatment, Cooling Frictional Prop: Silo design, Conveying Flow properties: Conveying As Food Moisture sorption properties: storage, drying, packaging Viscoelastic properties: Milling Rheological Prop: Extrusion Aerodynamic & Hydrodynamic: Cleaning, Conveying Physical Processes: Shelling, Cleaning, Polishing, drying, aspiration …etc. 1/10/2022 Applications example As Livestock Feed Mechanical Prop: Grinding and mixing Flow properties: Mechanical/pneumatic conveying Rheological Prop: Conveying as liquid feed D A N Dharmasena 11

1. 2 Physical characteristics Shape size Volume Surface area Density Porosity Colour Appearance Applications: Shape and dimensions • Design of grain cleaners, Cooling time calculation of fruits • Design of grain and other conveyors • Quality control of fruit and vegetables 1/10/2022 D A N Dharmasena 12 Skip next

Physical characteristics conti. . Density and specific gravity • Cleaning and separation, • sorting and grading Surface colour and appearance: • Colour sorting, Selective harvesting, grading 1/10/2022 D A N Dharmasena 13

1. 3 Mechanical Properties: Load deformation characteristics, • Impact and shear resistance: in size reductionenergy estimation • Static and sliding coefficient of friction: Handling & processing machine design, Design of storage structure • Compressibility: bailing, silo design, method of compressing 1/10/2022 D A N Dharmasena 14

Ideal elastic – demonstrated for less than 0. 1% strains – Reiner 1960 Not in existence for real materials!!!!! Loading Unloading < Linear elasticity Steel Hookean 1/10/2022 Unloading Non-linear elasticity of rubber Non-Hookean Elastic D A N Dharmasena < > > Loading Unloading Inelasticity of dry corn kernel Inelastic (viscoelastic) 15

Static compression Density kg/m 3 Vibration Impact Time minutes The highest compression of silage is obtained by? 1/10/2022 D A N Dharmasena 16

• Shearing resistance and cutting forces: • Paddy de-husking, peeling • Fruit and vegetable size reduction • Manual harvesting or • Harvesting machines (Cutting forces) 1/10/2022 17

1. 4 Thermal properties • Specific heat: Design of dryers, heat-processing systems • Othermal properties: Thermal conductivity, T. Diffusivity, Surface conductance, Emmisivity 1/10/2022 D A N Dharmasena 18

1. 4 Electrical Properties • In handling and processing • Electrical conductance – In MC determination • Capacitance – In MC determination • Dielectric properties – heating, microwave heating • Reaction to electromagnetic fields– electrostatic separation, Electroporation of Cell Membranes 1/10/2022 D A N Dharmasena 19

1. 4 Optical properties • Light transmittance and reflective properties for: • • Sorting and grading Maturity and surface colour determination Grain cracks Blood spots and green rot in eggs 1/10/2022 D A N Dharmasena 20