Combination of drying and extraction processes in processing agricultural products and medicinal herbs

Except for the freeze drying method, other drying methods cause loss of essential oils or volatile bioactive substances (perceivable through the odor generated during the drying process). On the other hand, the conventional extraction method produces a lot of waste products such as solid residues after extraction and unrecoverable solvents. To solve this problem, Dr. Pham Thi Thuy Phuong and colleagues have researched and come up with a feasible solution to combine both the drying and extraction processes in one device, in order to maximize the recovery of valuable products, and not create any waste (zero-waste), suitable for all types of materials. With those improvements, “Method and equipment for processing agricultural products and medicinal herbs in combination with drying and extraction process” has been patented No. 1-0028413 by the National Office of Intellectual Property, May 25, 2021, for Dr. Pham Thi Thuy Phuong and the authors.

The processing method includes the following steps. First, preliminary processing of agricultural products and medicinal herbs depending on the nature of each type of raw material and the requirements of each product. After preliminary processing, agricultural products and medicinal herbs are brought to the drying chamber. Microwave irradiation is carried out for drying materials in the drying chamber to conduct the drying process at a fixed temperature and under vacuum conditions. During the drying process, the steam and other components separated from the material are released from the drying chamber by gravity. Then, condensing the vapor mixture released from the drying chamber and collecting the extract; at the same time, separating the essential oil from the extract. As a result, agricultural products and medicinal herbs have been dried to the moisture content for preservation, and the mixture of extracts or essential oils is collected during the drying process.

The research team has tested this on lemongrass, ginger and grapefruit peel materials. The results show that the new method produces higher essential oil yield and antibacterial effect than the traditional method. Especially, the energy consumption is reduced many times compared to the traditional method.

Dried ginger after having essential oil extracted 

Ginger essential oil

Methods and equipment for processing agricultural products and medicinal herbs, in combination with drying and extraction, bring practical effects in life, helping reduce drying time and get the most out of medicinal ingredients in raw materials without additional energy costs, thereby reducing production costs and pollution, increasing equipment efficiency and providing added value. Information on the method and equipment was published in the Food Proc Eng Journal.

However, without active generation of microwave sources, and relying only on domestic supplies and materials, the research team can only develop the device at a household scale, even though the application to production is feasible. Hopefully in the near future, this device will be developed on a larger scale to produce products that not only have high economic value but also save production costs.

The authors 

Translated by Phuong Huyen
Link to Vietnamese version