Sun drying, hot air drying, contact drying, infrared drying, freeze-drying, fluidized bed drying, and dielectric drying etc. are available but which is the best in terms of shelf life extension of any foodstuffs!
Freeze drying is often used because of its ability to retain macro and most micro morphology. However, for best high resolution imaging, it is most often necessary to maintain the frozen state without drying, even while viewing within the SEM. This is because thawing can often alter the original morphology when considering high resolution. Therefor, a cold stage within the SEM is usually recommended to maintain the frozen state. A simple cold stage that can maintain temperatures just below freezing by a few degrees is usually enough for most such imaging tasks.
However, if small sample size can be tolerated one might want to try critical-point drying (CPD). Sample dried this way most often needs to be kept desiccated until one is ready to observe with the SEM, so that natural rehydration from room humidity does not occur before viewing. In this case, sample freezing is not necessary.
This just represents a couple of options for the case you have described.
Re-reading your question, I see you are not wanting to image the material. Freeze-drying is used to vacuum store most foods for 30 plus years. Sorry for the previous assumption.
The drying method depends on the type of product. There is NO unified drying method
There is no universal drying method. Each has advantages and disadvantages over the food in question. Besides, the cost is important.
it is depend the type of product
but when use any type of drying must be carefully clean and safety the food
It depends on the type of food you are going to dry. There is no universal drying method which is best for every food type.
Also, it depends upon what one wants to do with the food. Freeze-drying followed by vacuum packing, or packed with moisture eaters, can last 30 years or more and remain very edible.
Several drying methods of food preservation are available. It is my perception that one must look to the cost of the technique used for food preservation.The poor resource nations can not afford the expensive methods.
I agree with the explanation given by Prof.Var St.Jeor regarding the importance of freeze-drying followed by vacuum packing for preservation of food..
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