Which drying methods are practiced to dry plant biomass of spices, agricultural, horticultural, medicinal and aromatic plants?

In our lab to keep samples longer for secondary metabolite screening we had tried the lyophiliser and kept samples at -20C or -80C after that in sealed containers. But it is time consuming. I have found one quick method is using liquid nitrogen by which  one can quickly powder samples and keep them. Results are equally good.

Dear Dr. Chakraborty

How much sample (g or kg) can be stored in a lyophiliser and what happens to the sample in case of a power failure? What is the relative cost relative to other techniques in vogue?

For experimental purposes possibly it is OK but what about for industrial use? Is it cost-effective under Indian conditions?

Best wishes and good luck.

Dr. Rao- the drying method depends upon the market value of the commodity. If you think drying coriander leaves then tray drying at lower temperature say 50C is recommended whereas the cardamom or highly heat sensitive spices a combination dryer like tray drier/microwave or RF dryer is good enough. High cost products could be dried using Freeze drier which is really expensive and time consuming.  

I agree with Jasim

Dear Jasim Ahmed and Linda Dari

Thank you for your useful and economically viable tips. Many medicinal plants are either Sun or shade dried by small farmers which are free. Some small industries use hot air blowers or ovens for quick drying, but such quick drying under higher temperatures may some times result in thermal degradation of sensitive compounds. With technology, a number of methods have become available for a number of products and situations.

Best wishes.

The freeze-drying of samples is limited mainly by the way that they have little ability contributions samples are freeze-industrial yes, but who do not have access to them limited access? In addition, the cost of such a process is immense. Freeze-drying also has an effect on the raw material, it is not entirely so that all active substances are stabilized in the process. Another prodlemem from a consumer perspective, it is not exactly inviting look rough. So the fruit retain their shape, but are put off by the price. Rhubarb unfortunately resembles gray-brown foam (not attractive). Only leaves retain their color, but they are often large, long or so are cut into very tempting way. Therefore, it seems to me that still the best and economical way of drying, air szuszarniach (drum, blowing flow).

If we talk about drying in the sun, unfortunately commodities such as spices and medicinal firstly lose color, too much sun operates on the raw material, which also lose active substances. Drying must be used in shady spots, airy shelter to protect pred overexposure to sun, rain. It is best to dry in places protected from moisture. In such places, raw material dries evenly in a slightly longer period of time. Dryers are ideal.

The market value of a commodity should not affect the way of drying. Drying the raw materials we need to remember that the biological value presents itself in its composition containing active substances. I did not want me to buy a mint or thyme dried in the open air in full sun exploded on the ground or mats, where summer birds that make clear what. By purchasing any material which we must be sure that it meets quality standards in terms of body and purity of ingredients. And this is also our role, awareness growers, manufacturers or subcontractors various stages of production of raw herbs, spices, medicinal. Generally because they are the same plant, brought to various industries.

Dear Dr. Agnieszka

You have detailed very valuable and pertinent points for drying plant products. Drying for research is different from drying for commerce. The market value of the end product is a competitive factor for resource-poor customers. Quality takes second place and is relegated to the background as a personal choice. Visual quality, aroma, taste etc. take precedence to constituents' richness. It is true that Sun and shade drying have their disadvantages, but for a small farmer who is debt burdened and struggles to provide minimum amenities to his family, investment for dryers becomes a distant dream. Even today, many small and marginal farmers of spices, medicinal plants and agricultural crops (e.g. tobacco, vegetables, grain crops etc.) resort to no-cost Sun or shade drying.

Thank you for your contributions.

Best wishes.

I agree with Jasim Ahmed and Agnieszka. Drying of agricultural produce depends on its market value. We have dried aloe vera cube under freeze dryer but the output is very less. Freeze drying maintain the quality of product but costly in operation. In my opinion shade drying with circulation of hot air below 45 degree Celsius temperature best suited for medicinal plants.

Dear Vallabh

Thanks for your practical post.

anybody know anything about drying using (Supherb Dryer - Drying Cabinet), does it usefull for research purposes

Since research work is expected to go beyond  ending their journey on the shelf, the economic contribution of research , drying operation inclusive should be very important. This goes beyond the profit  made as a  small scale business or big industries. the nutritional and health implication matters. Cost effective dryer may be  designed  and employed but what is the implication on important  substance and essential active content of  these particular substance?  Solar dryer/cabinet  may solve the problem of  direct exposure to the  sun and  all other environmental contaminants. 

The nature of the material and the amount of volatile compounds present in the materials matters. it  may not be suitable to subject  Material with high Volatile compounds to drying in open environment like cabinet or oven. Spray dryer or freeze drying operation should serve better in this regards.

Has anybody used a food dehydration oven? Samples retain color, aroma and flavor.