Question

How does type of drying impact product quality? What are some pros and cons of each processing parameters (i.e. microwave, hot air, or freeze drying)?

How would compositional parameters of the food product effect drying?

What would be the effect of changing temperature of hot air drying?

How can you improve the rate of drying of a product in hot air convection oven set at a specific temperature?

Answer 1

How does type of drying impact product quality?

The quality of dehydrated products is affected by the type of specific drying method as well as the physical-chemical changes that occur during drying. They significantly affect the drying constant, colour, texture, density and porosity and sorption characteristics of materials.

Pros and cons of Freeze Drying Method

Pros:

1. Little or no shrinkage
2. Superior taste and aroma retention
3. Better rehydration properties, compared to products of alternative drying processes.

Cons: High treatment cost.

What would be the effect of changing temperature of hot air drying?

1. Many biochemical reactions can be induced by temperature increase in foods: Maillard reactions, vitamin degradation, fat oxidation, denaturation of thermally unstable proteins (resulting in variation of solubility or of the germinating power of grains), enzyme reactions (which can either be promoted or inhibited) etc.
2. Rate of browning reactions depends on temperature of drying.

How can you improve the rate of drying of a product in hot air convection oven set at a specific temperature?

1. Keep the oven door open slightly during drying so that moist air can escape while the heat stays in the oven.
2. Shifting the trays often is important for even drying because the temperature is not the same everywhere in the oven.