Engineering properties of biological materials
Before understanding what engineering properties of biological materials mean, let’s think about a simple question.
Imagine you are designing a dryer for grains or a machine for peeling a medicinal tuber crop. What would you need to know about the material before designing the processing machine for it? Would its size, shape, hardness, moisture content, or response to heat affect the design?
The answer is yes. To design an efficient machine, engineers first need to understand how the biological material (here grains or tuber crop) behaves during processing. These measurable characteristics are known as the engineering properties of biological materials.
Engineering properties are important when selecting food processing machinery, grain handling systems, drying equipment, testing instruments, and material handling equipment.
Why it is named as engineering properties?
These properties are fundamental to designing, analyzing, and optimizing processes and equipment in agricultural, food, and bioprocess engineering. Agricultural engineers need to understand the physical, thermal, mechanical and other properties of biological materials to design processes and machines for harvesting, handling, drying, milling, puffing, packaging, transportation etc.
What are biological materials?
Biological materials include anything natural we process in industries. In our subject, biological materials are grains, fruits, vegetables, seeds, or even wood and fibers. Grains, seeds, and other agricultural produce are inherently biological, meaning they are derived from living organisms and have unique characteristics influenced by genetics, environmental conditions (e.g., moisture, temperature) etc.
Why study engineering properties of biological materials?
Biological materials are different from metals or plastics. They are irregular, sensitive to heat, and can change over time. Knowing their properties helps us:
- To design better machines (Say for sorting, drying, mixing, grinding, heat exchangers)
- To save energy (By using just the right amount of heat or force during processing or designing machine)
- To maintain quality ( By ensuring food tastes good and lasts longer).
These are just some examples and study of engineering properties has more scope in various applications.
One Banana, Different Processing Needs
Take a simple banana. Depending on what we want to do with it, the properties we need to consider can be quite different.
If we are making banana chips, the size and shape matter for uniform slicing, while firmness helps the banana withstand cutting without getting crushed. Its moisture content is also important because it affects the drying or frying process and the crispness of the final chips.
Now, if the same banana is being converted into banana flour, moisture content and drying characteristics become more important. Size, maturity, and thermal behavior can also influence the drying process and quality of the banana flour.
Now what about handling and transportation? Here, we are more concerned about the banana’s weight, size, shape, mechanical strength, and tendency to bruise during handling.
So, there is no single list of properties that is equally important for every operation. Engineers first understand the processing task and then identify the properties that matter most for that particular job.
Engineering Properties and Selection of Agricultural Processing Machinery/Equipment
Engineering properties are widely considered for the design and selection of agricultural processing equipment and food processing machinery. Before developing equipment for a specific agricultural produce, engineers need to understand how the material behaves during handling and processing.
For example, During designing grain grain dryers, the moisture content and thermal properties of grains are important. Similarly, size, shape, density, and frictional properties influence the design of grain handling equipment, conveyors, hoppers, graders, cleaners, and storage systems.
Mechanical properties (hardness, toughness, and compressive strength) are important during selection of milling machines, grinding equipment, peeling machines, cutting machines, and other size-reduction equipment.
Therefore, engineering properties provide the scientific basis for choosing suitable agricultural machinery or any food processing equipment.
Let’s take another example of popping machine for corn or millets
To make a perfect popcorns or millet puffs, we need to understand:
- How much heat the kernel needs ? (thermal properties)
- How hard the outer coat is ? (mechanical properties)
- How much moisture it contains ? (moisture properties)
Understanding engineering properties makes it possible to turn raw biological materials into the products we use every day efficiently and effectively.
So how to define engineering properties of biological materials?
Engineering properties of food or biological materials are the measurable physical, thermal, mechanical, electrical, and chemical characteristics that are essential for designing, optimizing and controlling processes related to harvesting, handling, processing (such as drying, size reduction, mixing etc), storage, and packaging of these materials.
These properties help engineers understand how biological materials behave under various conditions, ensuring efficiency, quality, and safety in processing systems.
Some engineering properties of biological materials
- Physical Properties: Size, shape, density, porosity, surface area.
- Mechanical Properties: Hardness, elasticity, toughness, friction.
- Thermal Properties: Specific heat, thermal conductivity, diffusivity.
- Electrical Properties: Conductivity, dielectric properties.
- Rheological Properties: Viscosity, viscoelasticity.
- Moisture Properties: Water activity, hygroscopicity
Instruments Used to Measure Engineering Properties
Different engineering properties of biological materials require different instruments and testing methods.
Physical properties such as size, shape, density, porosity, and surface area can be measured using digital calipers, micrometers, weighing balances, graduated cylinders, bulk-density apparatus, and image-analysis systems. Mechanical properties such as hardness, elasticity, toughness, and friction are commonly evaluated using texture analyzers and universal testing machines.
Thermal properties (specific heat, thermal conductivity, and thermal diffusivity) can be determined using calorimeters, thermal conductivity meters, and thermal diffusivity analyzers. Rheological properties such as viscosity and viscoelasticity are evaluated using viscometers and rheometers. Moisture-related properties, including moisture content, water activity can be measured using grain moisture meters, water activity meters.
These instruments help engineers accurately characterize biological materials for the design and operation of agricultural processing equipment and food processing machinery. Engineering properties are measured using suitable laboratory instruments and agricultural product testing equipment, depending on the material and property being studied. For example, grain moisture meters are used to measure moisture content, while hardness, crispness can be evaluated using texture analyzer. Accurate measurement helps engineers understand material behavior and design efficient food processing machinery.
Summary
In summary, engineering properties of biological materials are essential for designing and optimizing processes in agriculture, food, and bioprocess industries. They guide engineers in ensuring efficient handling, storage, processing, and transportation while maintaining quality. This knowledge is crucial for solving practical challenges in the harvesting, processing, and utilization of materials like fruits, grains, seeds, and tuber crops.
