At Paradise Fruits, we offer contract drying facilities with the most modern
technology and expanding performance in northern Germany. One of our specialities is freeze-drying (lyophilisation) of fruit, vegetables and more.
Would you like individual advice on your products? Contact us today!
The gentlest way of drying
The practice of freeze-drying goes back as far as to the Incas at the high altitudes of the Andes who used the effects to their advantage. The water is removed from fruits or vegetables under vacuum. It is the gentlest method for drying food and other products. Because the structure of the molecules is preserved.
The physical effect behind this is the so-called “sublimation“: the direct transition from a solid to a gaseous state under special pressures and temperature conditions. Water is converted from fluid to steam in a vacuum with a controlled supply of heat. The same effect is also used with frozen CO2, known as “dry ice“. It converts into gas at one bar of atmospheric pressure, the well-known “dry ice fog“.
Advantages of Freeze-Drying:
Freeze-drying at Paradise Fruits
We carry out freeze-drying in plants with two chambers, which are connected by a valve. The first chamber contains the goods meant to be dried. They are placed in several layers on surfaces that can not only be cooled, but also heated. The layer thickness is usually in between 1 and 2 cm.
The second chamber, is quipped with a coil as a condenser, which can also be cooled or heated. In this chamber the low temperature, needed for the sublimation process is generated. In addition, this chamber is connected to a compressor to generate the necessary vacuum.
Three Phases of Freeze-Drying
Phase: At the beginning of the process, fruits or vegetables are cooled down considerably in the first chamber, to about -50 °C. The compressor then creates a vacuum in the second chamber with a maximum pressure of 6.10 mbar. Due to this strong negative pressure, the moisture exits the product chamber towards the second chamber. Compliance with the upper limit of 6.10 bar is crucial here. Because: sublimation (freeze-drying) only takes place up to this gas pressure.
Phase: The second chamber is slightly heated at the same time because sublimation requires energy, which is transformed into heat. Without these
measures, the temperature in the second chamber would drop. During this phase, the atmosphere in both chambers consists almost exclusively of water vapor, which precipitates in the form of ice on the cold coil of the second chamber. This step is called primary drying. In the process, most of the moisture is removed from the goods which are meant to be dried.
- Phase: In the last step, further heating of the coil takes place. In this so-called secondary drying process, the plant extracts most of the remaining moisture from the dry goods.
Proven and Versatile
We at Paradise-Fruits have been performing freeze-drying services for several decades – that’s how we gained extensive expertise.
Outside the food industry freeze-drying is used for pharmaceuticals and the production of medicines. Laboratories in fields such as chemistry, pharmaceuticals and biotechnology use freeze-drying to process some of their samples.
The process is basically identical, consisting of three phases: freezing, primary drying (sublimation) and secondary drying. However, industrial facilities for freeze-drying can be quite different. For example, some systems are designed in such a way, that only one chamber, instead of two, are needed. In some cases, freezing is carried out outside the drying plant. According to the size of the apparatus, machine manufacturers distinguish between laboratory equipment, pilot plants for process development and large-scale industrial production facilities.
Process development is essential in freeze drying: each product requires different settings for the process parameters like temperature, pressure and duration. For example: the vacuum in the second chamber must not be built up until the dry goods in the first chamber are completely frozen.
Otherwise, the material would expand in the vacuum and possibly overflow from its containers. We at Paradise Fruits have special pilot plants to determine the best possible parameter settings for each product.
We will be happy to advise you on your individual ideas.
Freeze-drying is perfect for all types of fruit that contain a high proportion of water. These include fruits like apples, pears, berries and grapes. Vegetables can also be freeze-dried with excellent results. Often freeze-dried vegetables are potatoes and carrots. Cereal products, bread and biscuits are not suitable for this process, as they contain too little water.
Get an overview of our Freeze drying portfolio.
Conclusion: Freeze-drying is best for Fruit and Vegetables
Freeze-drying is thus clearly the best process for turning fruit and vegetables into high-quality dried goods. Shape, color, aroma and ingredients are preserved far better than with conventional drying methods. Freeze-dried goods can be stored for a long time. In addition, their good solubility makes them ideal for the production of convenience products.
Freeze-drying is a job for specialists like us! We provide not only the required mechanical equipment, but also years of experience with this sophisticated process. You are wondering whether freeze-drying might be the ideal drying method for your product? Contact us today!
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