A)
What type of membrane allows water to move out of the food?
A semi-permeable membrane.
In osmotic drying, in which direction does water move?
From the food into the concentrated solution.
Which method generally provides better retention of colour, flavour, nutrients and structure?
Freeze drying
Why is freeze drying particularly useful for heat-sensitive products?
Because the product is processed at low temperatures, reducing heat-related damage.
What is one advantage of osmotic drying when used as a pretreatment?
It removes some water before further drying.
What can happen to some of the solute during osmotic drying?
Some solute can enter or diffuse into the food.
What is the major difference in the mechanism of water removal between the two methods?
Osmotic drying removes water through osmosis, while freeze drying removes frozen water by sublimation.
Name two applications of freeze drying.
Instant coffee and fruits/vegetables.
Why does freeze-dried food require careful packaging?
The dried product is porous and highly sensitive to moisture, and it can also be fragile.
A company wants a low-cost drying method but does not want sugar or salt to enter the food. What problem could arise if osmotic drying is selected?
Osmotic drying can cause uptake of the solute from the surrounding solution, potentially changing the food’s composition and sensory properties.
A food is immersed in a concentrated sugar solution, but no water moves out. What essential condition of osmotic drying may be missing?
There must be a difference in solute concentration/osmotic pressure between the food and the surrounding solution.