Textural changes of IQF fruits and vegetables during freezing

People often ask themselves about the changes of texture in IQF fruits and vegetables and whether the freezing process means a loss in nutrients. Questions like these can be answered only by studying the effect of freezing on various plant tissues.

As you may know, most fruits and vegetables contain over 90% water. The cell walls are responsible for the support structure and texture of the fruit or vegetable, and they contain this large quantity of water and other chemicals. This is the reason why freezing fruits and vegetables mainly means freezing the water in the cells walls.

In the freezing process, water expands and forms ice crystals, which break the cell walls. Therefore, the texture of IQF fruits and vegetables will be softer compared to the texture of the fresh products. This textural change is mostly noticeable in IQF fruits and vegetables since they are generally consumed raw.

The recommended freezing rate

The key to preventing and controlling the cell wall rupture is to freeze fruits and vegetables as quickly as possible. In the IQF freezing process, a large number of small ice crystals are formed. IQF fruits and vegetables contain lots of small ice crystals, which create less damage in the cell walls compared to the few large ice crystals produced in a slower freezing process.

The nutritional value of frozen fruits and vegetables

Freezing, when properly done in an IQF tunnel freezer, is a method of food preservation which can save a large quantity of nutrients. In order to maintain the best nutritional quality for IQF fruits and vegetables, it is essential to follow all the necessary procedures of the freezing process.

Dehydration

Dehydration is one of the most important aspects of the freezing process because it is less obvious and more difficult to quantify — and has a great economic impact. Dehydration is the result of the imminent loss of water vapours that happens when products are exposed to air. In the case of IQF fruits and vegetables, dehydration is significantly reduced due to two factors:

• If the temperature of the products is rapidly reduced, this lowers the evaporation rate (the rate at which water is transferred from the product into the air).
• IQF fruits and vegetables benefit from the short period of time in which the water is evaporating at a higher rate. But in order to achieve a fast freezing, cold air is not enough. Cold air must be evenly distributed over the surface of the product with the help of an effective airflow, and this can be achieved in an IQF freezing tunnel.

The IQF designed by OctoFrost features high-performance fans and perforated bedplates, which distinguish this tunnel freezer from the traditional solutions. In the OctoFrost IQF a unique airflow is created, which, combined with the movement of the bedplates, is able to maintain an efficient separation of the products and to protect even the most delicate products.

IQF fruits and vegetables benefit from optimal airflow and pressure ratios during the freezing process, due to aerodynamics controlled and adjusted in separate freezing zones. This allows for dehydration to be kept at a minimum for IQF fruits and vegetables, which keep their natural appearance with a reduced level of fines or lumps. In addition, snow formation is prevented for OctoFrost IQF fruits and vegetables, which enables many hours of valuable uptime between defrost.