A3 - Quantitative indicators for energy, water and raw material use

Definition drying of food products

Removing water from a solid or liquid feed by using (hot) air

Examples of food driers

• Cabinet (tray) driers or belt driers

  • For vegetables, fruit products, breakfast cereals

• Bin driers

  • Grain

  • Heated air is forced upward through the mass.

  • Moisture is removed gradually from bottom to top.

  • Slow but cost effective

• Spray drying

  • From liquid to powder

  • Milk powder, instant coffee

• Fluidized-bed driers

  • Peas, sliced vegetables, grains, powder.

  • Hot air is blown through a perforated bed, causing the particles to become suspended and behave like a fluid.

• Freeze drying

  • Chicken meat or mushrooms for dry soup mixes.

  • Freeze → lower pressure → water to gas.

What foods are produced by spray drying?

• milk powders

• Instant coffee and tea drinks

• Powdered egg product

• Cheese powders

• Soymilk powder

It is important for these powers that when they come in contact with water that they solubilize and become the original product again.

Separation

• Can be done by centrifugation

  • Liquid/liquid separation

  • Liquid/Solid separation

  • Liquid/liquid/solid separation

Types of membrane filtration

From largest to smallest pores:

• Microfiltration

• Ultrafiltration

• nanofiltration

• Reverse Osmosis

• W – Wise

• M – Monkeys

• C – Can

• P – Paint

• B – Beautiful

• S – Scenes

What is ultrafiltration?

• Removal of macromolecules from water

• Retention/rejection for proteins high, retention/rejection for small molecules low.

• Relatively low pressure and high fluxes.

Permeate recovery

Flow of the permeate relative to the feed.

Says something about flow

Rejection coefficient

R = 0 → component permeates freely through the membrane

R = 1 → component is completely retained by the membrane

R is different for different components.

Says something about concentration

Removal of low-molecular weight components from water

• Desalination

• Water treatment

• Concentration

• Dealcoholizing

• Flux and retention determined by membrane

• Pressure-drive process, moderate cross-flow velocities.

Retentate vs Permeate

Permeate goes through membrane, and retentate does not.