There is a tremendous range of sophistication in the
processing of herbs from crude herb material to highly
concentrated standardized extracts. Nonetheless, there are some
common stages. This document provides an overview of some of
these processes in the production of herbal products, and the
machines that perform these functions.
When plants are collected form their natural habitat, they are said to be "wild-crafted". When they are grown utilizing commercial farming techniques, they are said to be "cultivated". A collection of plants from cultivated sources ensures that the plant collected is the one that is desired. When an herb in wild-crafted, there is a much greater chance that the wrong herb will be picked, a situation that could lead to serious consequences. The use of analytical techniques can be employed to guarantee that the plant collected is the one desired.
In the United States marketplace, herbs from all over the world are marketed. The collectors of these herbs vary from uneducated natives and self-proclaimed "herbalists" to skilled botanists of professional training.
The mode of harvesting varies from hand labor to very sophisticated equipment. The mode is not as important as the time of harvesting. A plant should be harvested when the part of the plant being used contains the highest possible level of active compounds. Again, this is ensured by the use of proper analytical techniques.
After harvesting, most herbs have a moisture content of 60-80%, and cannot be stored without drying. Otherwise, important compounds would break down, or microorganisms would contaminate the material.
The majority of herbs require relatively mild conditions for drying. Commercially, most plants are dried within a temperature range of 100-140 degrees F. During drying, the plant material must not be damaged, or suffer losses, that would prevent it from conforming to accepted composition standards. With proper drying, the herb's moisture content will be reduced to less than 14%.
Garbling refers to the separation of that portion of the plant to be used from other parts of the plant, dirt, and other extraneous matter. This step is often done during the collection process. Although there are machines that perform garbling, usually garbling is performed by hand.
Grinding, or mincing, an herb means mechanically breaking down either leaves, roots, seeds, or other parts of a plant into very small units ranging from larger course fragments to fine powder. Grinding is employed in the production of crude herbal products as well as in the initial phases of extracts.
Often the material has to be pre-chopped, or minced, before feeding it into a grinder. In the process of grinding, a number of machines can be used, but the most widely used is the hammer mill. These machines are simple in design. The hammers, arranged radially, follow the rotation of the shaft to which they are attached, breaking up the material that is fed into the machine from above. On the walls of the chamber is a grid, which determines the size of the material that is passed through it. Other types of grinders include knife mills and teeth mills.
The process of extraction is used in making tinctures, fluid extracts, and solid extracts. Extraction, in the context of this document, refers to separating by physical or chemical means the desired material from a plant with the aid of a solvent. In the United States health food industry, most extracts utilize alcohol and water mixtures as solvents to remove the soluble compounds from the herb. The exceptions are liposterolic extracts, which are produced either through the use of lipophilic solvents or with the aid of hypercritical carbon dioxide.
Most extracts that are produced by small manufacturers use maceration procedures. The simplest process consists of soaking the herb in the alcohol/water solution for a period of time, and then filtering. Typically, this process will yield a lower quality extract at a higher price because the solvent, typically alcohol, cannot be reused as it is by larger suppliers of dry powdered extracts. Since tinctures are 1:5 concentrates; this means 80% of the bottle is alcohol & water, and only 20% herbal material. In essence, the cost of the alcohol is a major portion of the retail price of the tinctures. Tinctures are not as cost effective, nor are they as stable, as dry powdered extracts.
Larger manufacturers utilize more elaborate techniques to ensure that the herb is fully extracted and the solvent is reused. For example, a counter-current extraction process is often used. In this process, the herb enters into a column of a large percolator composed of several smaller columns. The material to be extracted is pumped through the different columns at a given temperature and flow speed, where it continuously mixes with solvent. The extract-rich solvent then passes into another column, while fresh solvent once again comes into contact with herbal material as it is passed into a new chamber. In this process, complete extraction of health promoting compounds can be performed. The extract rich solvent is then concentrated by techniques described below.
After extraction of the herb, the resulting solutions can be concentrated into fluid extracts or solid extracts. Large manufacturing operations utilize techniques and machines, such as thin layer evaporators, that ensure the extracted plant components are not damaged. These machines work by evaporating the solvent, thus leaving the plant compounds behind. The solvent vapors pass into a condenser whereby they return to a liquid state, and can then be reused. The result is separation of the extracted materials from the solvent such that the final product is a pure extract, and the solvent can be used again and again.
Although there are still a number of liquid form extracts on the market (tinctures, fluid extracts, and soft extracts), the preferred industry method is to dry the extract to a solid form. The main reasons are greater chemical stability and reduced cost (alcohol is often more expensive than the herb itself). Tinctures, fluid extracts, and soft extracts are easily contaminated by bacteria and other micro-organisms. Liquid forms of extracts also promote chemical reactions, which may tend to break down the herbal compounds.
A number of drying techniques are employed in the herbal processing industry, including freeze-drying and spray-drying (atomization). The result is a dried powdered extract that can then be put into capsules or tablets.
The same excipients used in the manufacture of pharmaceutical drug preparations, as well as vitamin and mineral supplements, often are used in the production of tablets and capsules containing herbs or herbal extracts. Many manufacturers will provide a list of excipients contained in their products. Viable Herbal Solutions does not use excipients of any kind in it's all-natural botanical formulations.
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