Unit 7 Working with Complex Food Systems
720
Separation processes can be either mechanical or chemical.
Mechanical operations are based on physical properties of food.
Chemical separations depend on how food components react on a
molecular level. Mechanical methods include separation by physical
properties, density, and addition of force. Centrifugal force, pressure,
and magnetic force can all be used to speed separation processes.
Chemical separation methods include the use of solvents,
crystallization, precipitation, evaporation, and distillation. Solvents
can be used to remove desired or unwanted food components.
Crystallization separates the solute from the solvent in a hypersaturated
solution. Creating new chemical compounds in solutions can allow
solutes to precipitate out of the solution. Evaporation and distillation
involve the removal of water from a solution. In distillation, the vapors
are collected.
Some food components are separated by passing through barriers.
The barrier processes include filtration, osmosis, and reverse osmosis.
Filtration techniques use porous paper to trap solids. When separation
is needed at the molecular level, semipermeable membranes are used.
Digestion is the body’s complex procedure for separating foods
into usable nutrients. Metabolism is the chemical reactions that occur
within the cells and involve the exchange energy. As in barrier
separation techniques, the body uses semipermeable membranes
and osmosis to separate and use nutrients.
1. What is the difference between sorting and grading?
2. Describe three ways foods are separated based on density.
3. How does the food industry speed up the processes of separating
foods by density?
4. List two foods that are separated from their sources by pressing
or milling.
5. Describe one way solvents are used to chemically separate a food.
6. How are particles chemically removed from a mixture using
precipitation?
7. What is the difference between evaporation and distillation?
8. What type of barrier separation method is used to remove visible
solids from solutions?
9. Explain what happens during reverse osmosis and give an example
of when this process might be used.
10. Why are semipermeable membranes specially designed for
each use?
11. List and explain the two basic types of metabolic reactions.
12. What is the solvent for all metabolic reactions within cells?