Freezing is one of the ways to preserve food that has been done by humans in the past. The Eskimos used glaciers at the poles to keep their prey. With the passage of time and the advancement of science and technology, mechanical methods of producing cold water using ammonia were formed, and in the 19th century, for the first time in America, Mr. Clerence birdseye) was able to offer the first sample of consumable frozen materials.
Freezing products quickly and separately is one of the new methods of freezing in Iran, which today has an important place in the country’s food industry.
Types of fast freezing methods:
- Using cold air
- Freezing by indirect contact
- Immerse frozen products
Freezing with cold air
In this method, to reduce the temperature of the products, high air with low temperature is used around the products to lower their temperature. Of course, depending on the requirements, there may be changes in how the air around the products.
But most of the time, the mentioned method is used to lower the temperature of the desired products. In this method, the design of the freezer used is done in such a way that the air can easily move in all parts of the products.
In this method, which is used in high-speed air and ground models to reduce the temperature of products with high-speed wind. Sometimes the products are moved inside the freezer with the help of a conveyor so that the cold air reaches all parts of the products for cooling.
Also, using carts containing products and directing them to the desired environment, can reduce the temperature of products in the environment and bring it closer to freezing temperature. This method will be effective for freezing more food, especially for a variety of meats such as chicken and beef.
Freezing by indirect contact
Indirect freezing is done by placing food on a cooling plate. As the food is placed on the cooling plate, the temperature of the products decreases depending on the level of contact with the plate. Of course, this method will be justified for products that need to be frozen in small volumes.
There is a type of plate designed for plate freezers, which has a set of horizontal and vertical plates for product placement. Then, after placing the food between these plates, cold air is passed around the food for rapid freezing of the products with high intensity. Until the food is completely frozen.
Immersion freezing
In this method, sodium chloride solution or sugar is used to cool the desired products; Because this liquid, despite being conductive, reduces the temperature of food very quickly. The advantage of this method is that the food can be frozen easily without being piled on top of each other, or losing their texture and composition.
One of the main disadvantages of this method is the possibility of penetration of the prepared solution into food packages. Therefore, sugar is used instead of salt to freeze fruits such as oranges, so that the absorption of the solution in the fruits does not cause any problems in their taste and quality.
The method of using salt solution is also used to freeze seafood such as shrimp and fish that will be well preserved in the presence of salt. To prevent the surface of the thin coating on the food packaging from drying out, ice in the liquid to be frozen is used.
What is the Rapid Freezing Method (IQF)?
The word IQF stands for Individual quick freezing. This technology maintains the products in such a way that their quality is the least different from the new type.
Freezing of fruits and vegetables by IQF method:
In technology (IQF), fruits and vegetables are frozen at a temperature of -40 ° C and through a rapid freezing tunnel, in weightlessness (suspended state) for several minutes, the high freezing speed causes water to The tissue between plant cells does not have the opportunity to form ice crystals, resulting in much less damage to plant tissue and cells, and this preserves the quality, freshness, aroma, taste, properties and vitamins of frozen food. Becomes. Weightless conditions also cause vegetables and fruits to be frozen separately and individually.
Freezing of fruits and vegetables in the freezing tunnel is done in two ways:
- Cold air passes by the product
- Immerse products in liquid nitrogen at very low temperatures
Products that can be frozen by the IQF method are:
1- Fruits include strawberries, cherries, mangoes, raspberries, kiwis, pears and…
2- Non-leafy vegetables such as green beans, green beans, peas, okra, corn, onions, squash, celery, carrots, beets, garlic, bell peppers and…
3- Leafy vegetables such as mixed vegetables (turmeric, jam, pilaf, etc.), parsley, mint, tarragon, savory, parsley, basil, etc.
4- Semi-prepared potatoes
5- Grilled and fried products such as fried onions, grilled eggplant, fried vegetables and…
Freezing is one of the ways to preserve food that has been done by humans in the past. The Eskimos used glaciers at the poles to keep their prey. With the passage of time and the advancement of science and technology, mechanical methods of producing cold water using ammonia were formed, and in the 19th century, for the first time in America, Mr. Clerence birdseye) was able to offer the first sample of consumable frozen materials.
Freezing products quickly and separately is one of the new methods of freezing in Iran, which today has an important place in the country’s food industry.
Types of fast freezing methods:
- Using cold air
- Freezing by indirect contact
- Immerse frozen products
Freezing with cold air
In this method, to reduce the temperature of the products, high air with low temperature is used around the products to lower their temperature. Of course, depending on the requirements, there may be changes in how the air around the products.
But most of the time, the mentioned method is used to lower the temperature of the desired products. In this method, the design of the freezer used is done in such a way that the air can easily move in all parts of the products.
In this method, which is used to reduce the temperature of products with high-speed air in various air and ground models. Sometimes the products are moved inside the freezer with the help of a conveyor so that the cold air reaches all parts of the products for cooling.
Also, using carts containing products and directing them to the desired environment, can reduce the temperature of products in the environment and bring it closer to freezing temperature. This method will be effective for freezing more food, especially for a variety of meats such as chicken and beef.
Freezing by indirect contact
Indirect freezing is done by placing food on a cooling plate. As the food is placed on the cooling plate, the temperature of the products decreases depending on the level of contact with the plate. Of course, this method will be justified for products that need to be frozen in small volumes.
There is a type of plate designed for plate freezers, which has a set of horizontal and vertical plates for product placement. Then, after placing the food between these plates, cold air is passed around the food for rapid freezing of the products with high intensity. Until the food is completely frozen.
Immersion freezing
In this method, sodium chloride solution or sugar is used to cool the desired products; Because this liquid, despite being conductive, reduces the temperature of food very quickly. The advantage of this method is that the food can be frozen easily without being piled on top of each other, or losing their texture and composition.
One of the main disadvantages of this method is the possibility of penetration of the prepared solution into food packages. Therefore, sugar is used instead of salt to freeze fruits such as oranges, so that the absorption of the solution in the fruits does not cause any problems in their taste and quality.
The method of using salt solution is also used to freeze seafood such as shrimp and fish that will be well preserved in the presence of salt. To prevent the surface of the thin coating on the food packaging from drying out, ice in the liquid to be frozen is used.
What is the Rapid Freezing Method (IQF)?
The word IQF stands for Individual quick freezing. This technology maintains the products in such a way that their quality is the least different from the new type.
Freezing of fruits and vegetables by IQF method:
In technology (IQF), fruits and vegetables are frozen at a temperature of -40 ° C and through a rapid freezing tunnel, in weightlessness (suspended state) for several minutes, the high freezing speed causes water to The tissue between plant cells does not have the opportunity to form ice crystals, resulting in much less damage to plant tissue and cells, and this preserves the quality, freshness, aroma, taste, properties and vitamins of frozen food. Becomes. Weightless conditions also cause vegetables and fruits to be frozen separately and individually.
Freezing of fruits and vegetables in the freezing tunnel is done in two ways:
- Cold air passes by the product
- Immerse products in liquid nitrogen at very low temperatures
Products that can be frozen by the IQF method are:
1- Fruits include strawberries, cherries, mangoes, raspberries, kiwis, pears and…
2- Non-leafy vegetables such as green beans, green beans, peas, okra, corn, onions, squash, celery, carrots, beets, garlic, bell peppers and…
3- Leafy vegetables such as mixed vegetables (turmeric, jam, pilaf, etc.), parsley, mint, tarragon, savory, parsley, basil, etc.
4- Semi-prepared potatoes
5- Grilled and fried products such as fried onions, grilled eggplant, fried vegetables and…