I currently work on lyophilization of fruit juices, but I saw that the final product is sticky and it cannot be converted into powder. Do you think that several agents are needed for this process (such as maltodextrin)???
your sample of fruit juices are contains a mixture of components therefore you have got an oily mixture. As you know the role of lyophilization is to remove the solvents (H2O) under cooling condition with vacuum . you need to separate your crude mixture by the traditional techniques ( solvent extraction) or chromatographic methods like, ( TLC ,CC , HPLC....etc). this will make your sample in solid state.
Method of manufacturing powdered fruit juice using dextran
US 5118517 A
U CAN USE STARCH, Arabic gum, maltodextrin 8%
The dehydration by atomization and the freeze-drying are two methods usually used nowadays to dry food. During the dehydration by atomization, liquid foods are reduced powder fine. The natural and artificial preparations and the powdered milk are two examples of dehydration by atomization. The freeze-drying consists in freezing a food at first, then in eliminating the ice , leaving only a dry, porous, high-quality food.
Please see the link below, this review article on freeze drying of fruit juices and high value food items will be valuable for you:
http://www.sciencedirect.com/science/article/pii/S0260877400002284
What is the temperature of freezing that you are using, it must between -70 to -80C for about 24-48h depending of the volume of the fruits or sample,,,
Dear Malek Amiali,
Our lyophilizer is an industrial one (Millrock, Stellar Series) and its lowest temperature is -53. So, I cannot achieve the temperatures you told me. I tried to turn them into powder by adding some dehydrating agents, but it would be more compfortable and cheaper if I didn't need them.
You can try using dry ice to freeze your samples. Or you can mix your fruit extracts with other fruits that help to increase the glass transition temperature
There is a simple and easy way to solve your problem. You have to freeze again your freeze-dried product carefully, by dry ice or by liquid nitrogen, and crash your sample into powder by a simple grinding. Of course, your grinding device should be precooled too, but it is not absolutely necessary. Even the viscous gum can be easily crashed by this way.
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