Osmotic treatment before drying

Fruits are kept in a concentrated solution: part of the water comes out of the tissue, and dissolved substances can pass into the fruit. For fruit, this is often sugar syrup.

How it works

Two processes occur simultaneously: the loss of water by the fetus and the entry of sugars or other dissolved substances into it. This is partial dehydration and change in composition; usually drying or some other method of preservation is then required.

History

Combined process stage

FAO guidelines describe osmotic preparation before air, solar and vacuum drying. It does not stand out as a universal replacement for all subsequent operations.

Water and Sugar Transfer Study

The 2023 paper dipped apples into different sugar solutions and studied the driving force behind dehydration. The behavior of the tissue depended on the substance and concentration, and not just on the exposure time.

What changes in the product

Sweetness and composition vary

Sugar from the solution can increase the proportion of sugars in the pieces, and some of its own soluble substances come out. Therefore, the meaning of fresh or simply dried fruit does not describe the processed product.

Color, density and taste

Pre-soaking may affect the darkening and properties of the pulp. The result is determined by the solution and subsequent processing; softness and brightness do not prove the absence of additives.

Complete technology required

In FAO guidelines for tropical fruits, osmotic preparation is used before air drying. A wet fruit kept in syrup cannot automatically be considered a stable dried fruit.

Pros

• Some of the water is removed before the main drying.
• You can get a sweet fruity ingredient with the desired texture.
• The manufacturer can combine preparation with different methods of drying.

Limitations

• Added sugars may be present.
• The name alone does not reveal the concentration of syrup and the proportion of fruit.
• This is usually just a stage and not a complete storage solution.
• Osmotic treatment is not the same as blanching, sulfiting or frying.

Where is it used?

• Sweetened dried tropical fruits.
• Semi-candied fruits and ingredients for confectionery products.
• Fruit pieces before further processing.

When to choose

• You need a sweet additive for baking and its composition matches the recipe.
• The manufacturer indicates the fruit base, syrup and nutritional value of the finished product.

When to choose another option

• You need a product without added sugars, but the composition after impregnation has not been confirmed.
• The seller describes only soaking and does not know subsequent processing and storage conditions.

What to know before buying

• What solution were the fruits kept in: sugar, syrup or another composition?
• What drying method was used after impregnation?
• Are there added sugars, sulfites and other ingredients?
• Are the nutritional values ​​for the finished product or the original fruit?