by Eric Brand

In Korea, the most prominent method of herbal extraction relies upon small, pressure-based extraction machines. These “home extractors” are widespread in Korea, and they are a Korean invention that has had a dramatic effect on Chinese medicine worldwide. Their utility has caused them to spread outside of Korea, where they now dominate the landscape of hospitals and pharmacies throughout mainland China. Most of these extractors are essentially customized stainless steel pressure cookers, and they are generally paired with a packaging machine that dispenses the decoction into a durable, heat-stable plastic pouch. Korean-style extractors are currently in more widespread use than granules in both China and Korea.

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Pressurized Korean extractors are essentially a home model of the pressurized steel extractors used in the manufacturing of granules. They can typically cook 5—30 packs of raw herbs per batch, and have been shown to significantly surpass home decoctions in the extraction of a variety of herbal constituents. The decoction is packaged without air so it has a relatively long shelf life even without refrigeration. In Korea, many patients regularly take supplementing decoctions in this form, and many pharmacies and even grocery stores sell pouches of ginseng and velvet antler extracts. Practitioners often prescribe a formula for several weeks at a time, and this delivery form is ideal for these customized, high-potency, long-term formulas. Because extractors can essentially make raw herbs convenient for patients, the corresponding formula composition style tends to parallel traditional herbal formulation approaches.
Generally, this is an excellent system. Prescriptions can be customized from raw herbs, and the traditional decoction process can be replicated with significantly less labor. Patients receive their decoction in single-dose, durable, heat-resistant plastic pouches that can be easily transported, re-heated, and consumed as needed. The pressurized cooking system allows for an extract that surpasses the traditional home decoction in terms of potency and efficiency, and the process reduces the human error of home decoctions in addition to providing convenience.

The efficacy of these home extraction machines has been well-demonstrated, as literally millions of doses have taken by patients in mainland China and Korea using this method. However, despite their ease of use and efficient extraction capacity, the home extractors do suffer from a few limitations that are not shared by the commercial machines used to make granule extracts.
Commercial Granule Technology vs. Korean Pressurized Extractors
Korean extractors allow private practitioners and clinics to make customized formulas with greater potency than raw formulas. They are easy to use and the medicinals are able to cook together, which many practitioners regard as an advantage over mixing dried individual extracts. Control over temperature and cooking duration makes extractors easy to use, and their comparatively small capacity makes them versatile for customized formulas. Additionally, extractors are commonly used by hospitals or clinics that maintain secrecy over formula ingredients; for example, I studied at a hospital in Taiwan that had proprietary research formulas cooked in Korean extractors so that the staff could not leak information about the formulas under investigation.

Nonetheless, home extraction machines pose a challenge with retention of essential oils, whereas commercial operations typically have a more sophisticated method of capturing the oils and reintroducing them into the final product. While a few of the most expensive home extractors do have an added unit to capture essential oils, most of the home extractors do not. Instead, the oils can be captured by allowing the decoction to slowly cool without opening the pressure valve, but allowing the decoction to cool instead of packaging it immediately can potentially affect the shelf life and hygiene of the decoction. Furthermore, the pressure created in the extractor is usually used to effortlessly move the liquid from the extractor to the packaging machine after the decoction is finished. During this transfer to the packaging machine, steam is lost and some of the essential oils may dissipate. For this reason, home extraction machines ideally require one to cook delicate aromatic medicinals separately on the stove, and the short stovetop decoction is added to the packaging machine at the end. This takes extra effort and is often skipped, so home extractors often lose some essential oil in comparison to commercial operations that use a combination of pressure cooking and essential oil capture.

Temperature is another variable that should be optimized and controlled when making extracts. When water is heated under pressure, its boiling point can rise beyond 100 degrees Celsius (212 F). This increase in temperature may offer benefits such as increased solubility of active compounds; however, it does introduce an unknown variable into the equation, as historically the decoctions used were only able to extract whatever constituents came out at the natural boiling temperature of water.

The temperature of the water can be controlled in both small extractors and large-scale commercial pressure cookers. However, in a small extractor, the transfer of the decoction from the pressure cooking machine to the packaging machine is best achieved under a significant amount of pressure. This ideal pressure is typically achieved by bringing the water temperature up to 120 C (248 F) before packaging the decoction. The high temperature and pressure creates a very hygienic and potent extract, but the uniform use of high temperature extraction for all medicinals is common when using small extractors. By contrast, large commercial producers can research the optimal cooking temperature of individual medicinals; the extraction temperature can be better controlled for each individual product, and usually the liquid leaves the sealed pressure cooking container with simple gravity rather than by releasing pressure, so high temperatures and high pressure are not required (the receiving container is usually below the cooking container in a factory, whereas the packaging machine of a home unit is usually above the cooking machine, so it is requires pressure to push the liquid uphill).

Cooking duration is also relatively poorly controlled in a home extractor when compared to the commercial process. For example, when cooking da huang (Radix et Rhizoma Rhei), a short cooking time will produce a potent purgative effect, while a prolonged cooking time will reduce its purgative effect. The short cooking can be achieved by the factory by using an abbreviated cooking time, but the home extractor requires the “add at the end” (hou xia) medicinals to be cooked separately on the stove and added in at the end. The medicinals cooked in a home extractor are all generally cooked for a similar duration of time, because it takes about 30-40 minutes of cooking at peak temperature to build the ideal pressure required to move the liquid into the packaging machine.

Additionally, measurement is somewhat more precise when using commercial extracts instead of small extractors. Small extractors can control the amount of decoction dispensed per pouch, and it is generally quite easy to make the doses per pouch appropriate for each patient. While not lacking in clinical efficacy or ease of use, the home extractors are not able to achieve quite the same mathematical precision that one can achieve when using a precisely measured and openly labeled commercial extract. This degree of precision may not be necessary in clinic, but it is advantageous for easy calculations (or legal cases).

Unfortunately, the litigious nature of American society has hampered the market penetration of home extraction machines in the United States. Most practitioners are unclear exactly how the law classifies an extract for a patient that is cooked in the practitioner’s clinic. Does it fall under a food preparation license? Is it a dietary supplement, a tea? Does it need to be GMP? Clearly there is virtually no enforcement, no massive push by the FDA to crack down on small-scale licensed practitioners cooking up formulas for patients. Yet despite the apparent lack of lawsuits, many practitioners remain reticent to cook their own formulas in their office. The labor of cooking the herbs and cleaning the machines, coupled with the gray area of licenses and liability has caused this huge global TCM trend of home extractors to go largely untapped here in the US. Instead, US practitioners tend to favor granule powders or extracts that can be taken off the shelf and given directly to patients in a sealed bottle with full GMP compliance.
Despite these limiting factors of home extractors in comparison with large commercial approaches, they are clearly an excellent delivery system. The home extractors currently dominating the Chinese and Korean TCM landscape are one of the most prominent herbal medicine developments in our time, offering practitioners their own mini-factory, an intermediary choice between stovetop technology and full-scale industrial technology. Their popularity in Asia has reached a critical mass, many studies have been published that show favorable results when comparing pressure-cookers with home decoction methods. Seeing the quantifiable improvement in extraction efficiency achieved by cooking medicinals under pressure gives one an appreciation for the sophistication and science of the herbal medicine industry. As pressure cooking is only one aspect of advanced extract production, I suspect that in coming years we will see many more scientific reports that deepen our appreciation for the amazing developments in this modern age of herbal medicine.

Copyright Blue Poppy Ent. Inc., 2009. All rights reserved.