Asclepius Herbal Consultancy
Production Methods

Percolation contra maceration;
the art of capturing nature in a bottle

Many Phytopharmaceutical companies utilise either maceration or cold-percolation systems in the production of herbal extracts. The percolation method has many qualitative advantages over simple maceration, which is probably the most commonly used herbal extract production technique.

Both maceration and percolation rely primarily on the diffusion of the relatively high concentration of constituents in the herbal material into the extraction medium; containing a relatively lower concentration of constituents. However, there is also a rinsing effect involved in the extraction process, whereby the extractive substances from destroyed cells in the herbal material being processed are simply washed out, either by the movement of extraction medium through the herbal material, as is the case with percolation, or by regular agitation of herbal material undergoing maceration.


The percolation process provides the best scenario for ensuring an optimal degree of both diffusion and rinsing. During percolation, the herbal material is constantly exposed to a virgin extraction medium, thus ensuring that the highest possible diffusion gradient is maintained throughout the whole process between the herbal material under extraction and the extraction medium until exhaustion of the plant material is ultimately achieved.

When carried out effectively percolation can extract a much higher percentage of the constituent substances contained in the herb compared to other commonly used extraction methods.


During a maceration process however, the diffusion gradient decreases as the concentration of constituent substances rises in the extraction medium, and diffusion ultimately stops when there is an equal concentration of constituent substances in both the herbal material and the produced extract.

Preperation Nomenclature

From this it can be seen that the ratio nomenclature, which is often used to describe the ratio of herbal drug to extraction medium in a herbal preparation, is a rather misleading guideline regarding extract strength. In principle a 1:3 macerated extract could contain up to 50% less of the constituent substances than an effectively produced 1:3 percolation.

From an economical point of view percolation would appear to provide the best value in terms of raw material investment. In common production practice however, maceration and variations of the maceration process are often employed as they are simpler and less time consuming processes compared to the percolation method; even though at least 50% of the herbal constituents are ultimately thrown away in the wasted herbal material.


The difficulties encountered with percolation lie in the complex control parameters inherent to the percolation process. Many factors have to be taken into account when using the percolation method and the production practice requires a relatively high level of operator skill and experience; to ensure correct packing of the percolator in order to prevent clogging of the system and to adjust for the correct percolation rate (velocity).

In order to compensate for these process-related factors and to ease the production process, many producers compromise the percolation process in order to increase the functionality of the percolation apparatus. An example would be the funnel-formed percolator, where the percolation process occurs in a conically tapered system. This system has the advantage of been easier to pack. Unfortunately however, it suffers a major drawback. Due to the form of the system there is not a linear (lamina) flow of extraction medium through the system. The Weber effect of the funnel form causes an increase in percolation velocity through the system and Bernoulli’s principle dictates that this would increase turbulence in the extraction medium causing an increase in non-linear flow towards the funnel apex. As percolation relies primarily on diffusion it is important to reduce turbulence to a minimum and promote a lamina flow of the extraction medium through the herbal material.

Yet another parameter which is difficult to control in currently used percolation systems is the percolation velocity. There are many factors which influence percolation velocity: packing density of the herbal material, head-pressure of the extraction medium and the diameter of the exit from the system. A skilled operator has experience in packing the specific herbal material and knows how tight the material should be stamped to ensure a packing density that facilitates for a reasonable flow velocity. Finally, during the percolation process the operator has to constantly monitor and adjust the exit valve in order to control the flow velocity and compensate for variations in the head-pressure (which falls in a non-linear fashion in funnel-formed percolation systems).

Asclepius Herbal Consultancy has developed an automated computer controlled Percolation System (VCLF), which eliminates many of the difficulties encountered with the percolation process.






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