Osmotic Dehydration
Intensification of Drying Processes
Osmotic dehydration is primarily used as a pre-treatment in industrial and research processes, applied in scenarios where preserving sensory quality is a priority. Osmotic dehydration reduces drying time and energy consumption while better preserving the color, flavor, and nutrients of the food.
How does the process work?
Osmotic dehydration works based on the physical principle of osmosis, where water moves through a semi-permeable membrane (the cell wall of the food) from a less concentrated medium to a more concentrated medium.
In practice, during osmotic dehydration, the food is immersed in a concentrated sugar or salt solution. Since the concentration of sugar or salt is much higher in the solution than inside the food cells, water leaves the food toward the solution to reach an equilibrium in sugar or salt concentration.
Intensification of Osmotic Dehydration using Ultrasound
The integration of ultrasound technology in the food processing industry marks a significant advancement, especially in drying techniques. This approach uses ultrasound to create microchannels within food products, which profoundly affects the drying process. By implementing ultrasound pre-treatment with a bath or probe, it is possible to reduce drying time by up to 40%, along with a substantial decrease in energy expenditure. This method not only increases the efficiency of the drying process but also contributes to a more sustainable and economical production system.
Advantages of Osmotic Dehydration
Immersion in an osmotic solution reduces exposure to oxygen, inhibiting enzymatic browning. Additionally, the intake of solutes (such as sugars) can help fix natural pigments.
The solute layer formed on the food surface acts as a barrier, reducing the loss of aromas and flavors during subsequent drying.
Since a considerable portion of water (up to 50%) is removed in the osmotic stage, the time required in the oven or hot air dryer is drastically reduced.
It is possible to add components of interest, such as sweeteners, preservatives, or even enrich the food with bioactive compounds (fortification).
The reduction of water activity during pre-treatment initiates the microbiological and chemical stabilization of the product.
Tested Products
The technology has already been applied in the drying of apple, pineapple, cashew apple, sapodilla, melon, papaya, rose apple, sugar apple, banana, strawberry, and jenipapo.
