Mixing is a key operation for many food processors -- a necessity when two or more ingredients must be blended together. We are often asked the definition of mixing versus agitation or blending. Sounds simple enough, but not so when you add other "mixing" terms such as dispersing, hydrating, suspending or emulsifying! In other words, depending upon the ingredients involved, "mixing" or "blending" may not properly describe the operation required. The following are brief descriptions to define each situation:
The generic term for the operation encompassing all the variations that follow.
Typically a low speed blending operation with turbine type blades, or paddles.
Mixing or agitating two or more miscible liquids of similar viscosity (or solids only) and density, often done within a vertical helical screw blender.
Where the dissolution of a solid in a liquid is necessary, as with salt or sugar solutions. Simple agitation techniques are
normally sufficient, although high shear techniques are needed when other solids may block dissolution of the primary solid.
Mixing of two immiscible liquids, or a solid into a liquid to make a stable mixture. Dispersions usually involve
reducing the size of particles and agglomerations to allow more particle surface area to be wetted out. An example
would be liquid vitamins or corn syrup solids into water.
Similar to creating dispersions, but emulsions are more stable and complete. May be an "oil in water" emulsion where
water is the continuous phase and oil is the dispersed phase, or "water in oil" emulsion which is the opposite. Oil in water emulsions are the more difficult, and high energy high shear mixers are necessary. Mayonnaise is an oil in water emulsion.
Many ingredients are used as binding agents or stabilizing agents by "swelling" when activated under high shear, and attaching to other solid or liquid molecules. Hydrating
hydrocolloids such as gums, carrageenan, CMC, etc,. can be very difficult without the proper high shear equipment.