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A Quality of the drugs can be maintained without further lowering even if the
raw drugs is of the lower grade, when this method is adopted. Many
substitutes/lower grade plant products like immature tissues, fallen leavesfruits
and seeds, infected plant parts, etc., undergo faster deterioration at
higher temperature of drying.
The disadvantages of shade drying: The shade drying takes, more time,
space, manpower for attaining a lower level of moisture contents in the drying
process.
It also affects the quality of certain raw drugs in a different way. The moisture
removal takes place slowly. Hence the storage time increases. During this
period the chemical/enzymatic changes are possible in the stored tissues,
particularly if the drug is tender bark, fruit or leaf. Higher rate of growth of
microorganisms like fungus, microbes, virus, etc at higher moisture level for a
long period is possible. Hence quick or direct sun drying or artificial drying is
advocated for that type of drugs.
Depending upon the seasonal variations, the time taken for the shade drying
may vary significantly. Hence during rainy season, faster drying either in the
available direct sun light or using artifical devises is suggested.
Advantages and disadvantage of direct sun drying : It needs lesser time,
manpower, storage space and economical paramenters. It can also maintain
the quality of the drugs. But where the possibility of the loss of volatiles,
bleaching of the fine components, etc are not expected there this method has
disadvantage. However fermentation in fruity drugs like grapes, lemon,
gooseberry, etc., is higher. Here maintaining lower temperature for drying is
best. The quality of pepper, cardamon, cinnamon etc appeares to be very high
when dried in the shade. Drying in the shade is of great importance for all
spices, when the humidity in the atmosphere is low (like north Indian states).
However care may be taken for adopting suitable methods of drying where
humidity is high.
Advantages and disadvantages of direct or indirect heat drying: It is to be
remembered that in olden days, heat drying was possible only by placing raw
drugs above the fire wood, or on the surface where heat is available from the
fire or directly heated on the heated vessel. Under all these conditions
controlling the temperature is done arbitrarily. Hence, the possible chemical
changes can also be predicted, when the temperature varies without control.
The advantage of the rapid heating for drying method is that, enzymatic in vitro
changes can be arrested, the microbial infection and quality deterioration can
be prevented. For prolonged storages this method gives better results as the
moisture level can be definitely fixed at a known level below 6%. Space, time,
manpower etc can be reduced, so it is economically beneficial too. This method
may be opted provided other major quality parameters of the drugs are not
affected, like loss of volatiles, colour, sudden heat based changes etc. In the
modern systems controlled heating equipments are available and they have
many well known results and merits.
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