Freezing food is one of the most commonly used and beneficial preservation methods. Quick freezing food will involve converting the liquid ingredients in the food to a solid state of ice crystals, which will reduce water activity and the growth of microorganisms captured by shock. cold.
Normally when it comes to freezing, Pure or regular water will freeze at 0°C, while other foods, for example fruits and vegetables, Freezing temperature must be below 0°C, because these foods contain a lot of dissolved solids such as sugars and acids.
What is the principle of food freezing?
During freezing, products will cool below their freezing point but the product does not freeze immediately, a phenomenon known as supercooling. It is represented by the AB phase of the curve (Figure 1).
At the supercooled region, nucleation (nucleation) is the first and most important step in the formation of ice crystals during freezing. Here the temperature of the water will be lower than 0°C but it is still liquid. At this stage, even lower temperatures lead to the formation of ice crystals.
The second step is called the crystal growth phase. The heat release of crystallization increases the temperature (BC). Since food molecules contain a significant amount of water there, incremental freezing occurs. (as depicted in Figure 1).
Different water molecules gather around the nucleus and due to subsequent addition, crystal growth occurs. Nuclei can be of 2 types – homogeneous and heterogeneous. Homogeneous nucleation occurs when water is free of impurities and heterogeneous nucleation (catalysed nucleation) occurs when water molecules gather in a crystalline arrangement on nucleation such as the active surface. , this type of nucleation prevails in food systems.
In the next step, crystal growth around these nuclei occurs and as a result of ice crystal formation, heat of crystallization is generated, increasing the temperature of the cargo. Here Tes is represented by the line BC. Therefore, the time according to the solidification curve from initial cooling to point E of the curve is called the heat capture time. It determines how fast or slow the freezing process is. After this point, more ice crystal formation takes place and the temperature drops.
Advantages of freezing
o No loss of nutrients contained in the product
o Retain the freshness of products and foods.
o Retain color and flavor.
o Not contaminated with microorganisms.
o Non-respirable, hence longer shelf life.
Fast Freezing & Slow Freezing
Freezing process is divided into two types: slow freezing and fast freezing.
– Slow freezing cable: when the heat capture time is over 30 minutes.
– Fast freezing: The time to keep heat is less than 30 minutes.
During slow freezing, less nuclei are formed and as a result of slow freezing, a more concentrated solution is left in the intercellular spaces, causing osmotic and osmotic effects. liquid leaves the cell. This affects the disorder of the cells and they collapse and when thawed cannot regain their original shape. In addition, the crystalline forms are larger in size and penetrate the cell membrane, perforating the cell membrane and damaging the cell.
Whereas during rapid freezing, a large number of nuclei are formed, so there is a large number of smaller sized crystals evenly distributed in the cell and in the intercellular space. Since the process is very fast, no condensation effect occurs and the goods retain their original shape.
Fast Freezing Application
– Freezing seafood bars
– Fast freezing of agricultural products
– Fast freezing of fruits
ICE COOL Vietnam is a unit specializing in manufacturing and installing Quick Freezers today. We provide all equipment, production line technology and manual handover and operation instructions for business owners and manufacturing plants.
With many years of experience in the business of civil and industrial fast freezing machines. Any need for advice, investment, installation of durian quick freezer or other products. Please contact ICE COOL Vietnam at:
Hotline: +84 94 110 8888 for free and most thoughtful advice.
Or you can leave a comment below this article, we will contact you right away!