ENERGY RESOURCE SAVING TECHNOLOGIES OF DEHYDRATION OF MEDICINAL AND AROMATIC PLANTS
The world market development of plant products demonstrates growing demand for medicinal and aromatic raw materials that are widely used in pharmaceutical, perfume and cosmetic products, food production, etc. An important step in post harvesting storage of medicinal and aromatic plants is drying, which prevents spoilage of raw materials and increases the shelf life of the product. However, heat-sensitive plant components, such as biologically active compounds and essential oils are lost during drying at elevated temperatures. That leads to changes in the aroma, taste and color of dried herbs.
The purpose of the article is studies of dehydration processes of medicinal and aromatic plants to determine energy-efficient drying modes that ensure maximum preservation of biologically active compounds and essential oils.
The temperature of the drying agent plays the most important role in preserving of heat-sensitive components in dried herbs. The analysis of experimental data of temperature effect on content of essential oils showed that drying temperature of aromatic plants should not exceed the maximum allowable temperature of 35-40 °С. The effect of temperature, speed and moisture content of the drying agent on the kinetics of dehydration of peppermint herb has been studied. The experiments were carried out at the drying agent temperature in the range of 30-50 °С, its velocity – 1-2 m/s, moisture content of drying air – 6-14 g/kg d.a.
Significant dependence of drying process duration on heat-humidity parameters of atmospheric air was revealed. To create controlled drying conditions, it is proposed to dehydrate aromatic plants in dryers with a closed circulation circuit using a heat pump.
Energy-efficient drying modes for medicinal and aromatic plants with a variable degree dehumidification of drying agent have been developed, in which the temperature of the material does not exceed the maximum allowable, and aroma losses do not exceed 20-25% of the raw material. The use of a heat pump allows to reduce the specific energy consumption for drying in 2…3 times
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