When extracting plants, fungi, and other materials for medicinal use, the traditional method is called a hot water extract. This process is composed of two distinct steps, and the result is a potent, full-spectrum powdered extract. Two distinct steps are required to capture and concentrate the many different types of compounds present in the raw materials. Some compounds will be soluble in water, and other compounds will be soluble in alcohol. When a hot water process is used, both the water-soluble and alcohol-soluble compounds are captured.
Hot Water Extract Powders
Before the actual extraction process begins, several important steps must be carried out. This process is called preliminary preparation:
- Bulk collection of raw materials.
- Hand sorting and selection of raw materials (for quality) and washing.
- Powdering (grinding and/or crushing) and sieving of the powder to increase the surface area for better extraction.
Once the herbs have been gathered, sorted, washed, and powdered, they are ready for the actual extraction process to begin.
Stage One: Hot Water Processing
Within chemistry, water (H₂O) is called the universal solvent because of its ability to dissolve most substances. In fact, water can dissolve more substances than any other liquid, as explained by the Khan Academy. This makes water an important solvent in producing herbal extracts. Water is the primary extraction solvent used in hot water extract powders.
In the hot water processing step, the powdered herbs are combined with water and heated to between 100°C and 110°C. The exact temperature and duration of heating will vary depending on the herb being extracted and the desired final concentration (a 10:1 extract will take less time to produce than a 50:1 extraction). This process, called "stoving," may be repeated several times.
When the hot water extraction process is complete, the solution of herbs and water is vacuum-pumped to produce the desired concentration. The outcome is a highly concentrated combination of extracted herbs and water, which will go on to the next step.
Stage Two: Alcohol Precipitation
Once the desired compounds are captured using hot water, it is time to precipitate the mixture of herbs and water to separate what will become the powdered extract from the water. Essentially, alcohol precipitation allows the compounds that have been dissolved in water to be transferred back to the solids.
In this step, the concentration of herbs and water from step one is combined at a 1:3 ratio with alcohol (95% ethanol), so that for each part of herbs and water, there are three parts of alcohol.
This solution is agitated for 15 minutes and then set aside for 12 hours so that the desired compounds can be fully extracted into the alcohol.
Stage Three: Spray Drying
Once it has sat for 12 hours, the liquid and solids are separated (the water and alcohol are evaporated, leaving behind their extracts). Finally, the extract is spray-dried at a temperature of 70°-100° Celsius, and the resulting powder is further crushed, stirred, and sieved.
Other Extraction Methods
Because this extraction method is called a hot water extract, but in fact uses both hot water and alcohol as solvents, there tends to be confusion surrounding both what this process entails and how it differs from other extraction processes.
Traditional Herbal Extracts
Throughout history and across the world, humans have used herbs (including plants, fungi, and other substances) as medicine. Different extraction methods have been used in various traditions, including soups, teas, fat extracts such as medicinal oils and salves, and alcohol extracts such as medicinal beers, wines, and tinctures.
However, when referring to the modern, scientific application of using herbs as medicine and the use of those extracts, there are three main extraction methods:
- Hot water extract powders (discussed here).
- Ethanol/alcohol extract powders.
- Tinctures (ethanol/alcohol) extract liquids.
The Difference Between Ethanol/Alcohol Extract Powders and Hot Water Extract Powders
Hot water extract powders and alcohol extract powders are two distinct methods used in herbal extraction processes. Hot water extract powders primarily utilize water as the extraction solvent, employing heat to dissolve water-soluble compounds. This method captures a wide range of medicinal constituents found in plants. On the other hand, alcohol extract powders involve combining concentrated herbs and water with alcohol. This process allows for the transfer of compounds dissolved in water back to the solids. Alcohol precipitation is particularly effective at extracting alcohol-soluble components. Both methods have their advantages and applications in herbal medicine, with hot water extracts being suitable for capturing a broad spectrum of compounds and alcohol extracts specializing in alcohol-soluble constituents. For more information on alcohol extract powders, you can refer to our comprehensive article on the topic ( Producing Alcohol Extract Powders). The choice between the two methods depends on the desired outcome and the specific properties of the plant material being extracted.
The hot water extraction method is by far the most widely employed extraction method in producing extract powders for medicinal use. What is commonly believed to involve only a single step of extraction using water actually occurs in two steps (as shown above), one involving hot water and one involving ethanol (alcohol). This is an important extraction method, and many of the scientific studies on the uses of medicinal herbs use this process (as can be seen by searching NCBI's PubMed or Google Scholar).