Freeze dried fruits are to choose some season fresh fruits, which were just picked, and frozen them immediately. With the help of vacuum dewatering technique, the solid water is directly sublimated into a gaseous state. And then water vapor becomes into frost in the condenser. When the drying process is over, frost will thaw and melt away.
On the basis of keeping the original physical chemical structure of fresh fruit, vacuum dewatering technique dry the fruit by sublimation, which preserves the original color, smell, taste, nutrition and appearance. What’s more, the preservation rate of inherent nutrient is up to 96%. With its good rehydration and zero additive, freeze dried fruit becomes a kind of natural and healthy food.
Generally speaking, the production process of freeze dried fruit includes raw material selection, cleaning, peeling, slicing, loading plate, freezing, sublimating and drying, packaging, the appearance of finished product, etc. Now let us analyze it step by step.
Step 1: Raw material selection
The standard of selection is really strict. We usually choose fresh fruits with normal color, moderate maturity, moderate hardness and similar size. And there is no decay and deterioration.
Step 2: Cleaning
Put those fruits into clean water for rinsing. And then fish them out and drain them with the sieve.
Step 3: Peeling
In this step, we need to peel the skin of fruits. If the fruit contains the core, we also need to remove the core, such as apple, plum, mango, etc.
Step 4: Slicing
We use stainless steel special tools for slicing. The speed is really fast, which can prevent raw materials exposing to the air for a long time. And the thickness of fruit slices is between 3-5 millimeters.
Step 5: Loading plate
Raw materials are uniformly laid out. And make sure that there is no stacking.
Step 6: Freezing
The suitable temperature for freezing is minus forty degree centigrade. And fruit slices need to stayed for six hours at the this temperature.
Step 7: Sublimating and drying
Put raw materials into cold well and precool them for thirty minutes. Then put them into freeze dryer and vacuum the machine to at most 10Pa. Then warm raw materials for four stages.
First, heat them at the temperature of 5 degree centigrade for 120 minutes. Second, heat them at the temperature of 10 degree centigrade for 120 minutes. Third, heat them at the temperature of 20 degree centigrade for 240 minutes. At last, heat them at the temperature of 25 degree centigrade for 120 minutes.
Step 8: Packaging
After freezing and drying, pick fruits out and place them in an proper environment, where the relative humidity is less than fifty percent and the temperature is between 22 and 25 degree centigrade.
Freeze dried fruits should be stored in a cool and dry place. If conditional, it will be better to place it in an environment with low temperature and low humidity. Usually, the shelf life is two years.
Last but not least, here is a little hint. When it comes to different freeze dried fruits, the temperature of vacuum dewatering technique that we mentioned above may be different. If you want to know more other technical parameters, welcome to get in touch with Zhengzhou Rich Foods Co.,Ltd.