The Crucial Importance of Correct Processing

The all-important biomedical activities of aloe juices and extracts depend critically upon applying strict rules of processing and handling. These determine whether or not the labile biochemicals in the living plant are successfully stabilised during manufacture and, subsequently, during distribution and storage. This newsletter reviews this important aspect of Aloe.

Introduction

Getting oneself supplied with good Aloe vera Extract is not so easy as one might think. One problem is that the Aloe Industry has been very prone, unfortunately, to misleading practices, with suppliers often diluting the valuable Aloe Extracts with water to increase their profits - even to the extent of selling virtually pure water as Aloe. In other cases suppliers have extended the extracts with a combination of water and maltodextrin - a cheap carbohydrate product from corn starch - just to make it look as though the solids component of the Aloe has not been diluted. That is one of the problems with Aloe and it will be dealt with fully in Newsletter No 11.

The other major obstacle to getting really genuine Aloe does not relate to dishonesty, but rather to lack of knowledge or a lack of tightness of management control in the Aloe processing operations. The problem is that many of the active ingredients of Aloe are distinctly labile, that is to say, that if you subject them to even slightly adverse conditions, then they spontaneously undergo chemical changes which cause them to lose the biomedical activity, which is what the purchaser of Aloe is trying to buy.

The Active Principles of Aloe and their Survival of Processing

The known active principles of Aloe are (1) Plant sterols (2) Natural salicylates (3) The enzyme bradykininase (4) A probable unknown antihistamine substance (5) Plant hormones of the group known as auxins (6) Plant hormones of the group known as gibberellins (7) The special carbohydrate of Aloe, known as "glucomannan", which in reality represents several active principles, because it comprises fractions of different molecular weights which have different effects. These active principles have been discussed already in Issues 1, 2 and 4.

It is clear that these various active principles have differing degrees of lability, i.e. will vary in their susceptibility to inactivation under conditions of processing. Indeed, since they are of a number of widely differing chemical types we can be sure that some types of processing operation will adversely affect one active principle and another type of processing operation will adversely affect different active principles. This makes the problem complex, because different parts or aspects of the product become vulnerable at different stages of the processing operations.

The Steps in Aloe Processing and the Vulnerability of Biomedical Activity

When we come to consider the steps in processing we have to consider that there are two main products involved, either gel or whole leaf extract, and that different processing steps are needed for each of these products. However, they both begin in the same way, with harvesting the leaves and transport off the field to a place where the first steps of processing are carried out. Usually there will also be a holding period when the delivered leaves are awaiting processing. What is important here is (1) the time taken from the moment of cutting to reaching storage (2) the conditions under which the leaves are transported from the field to the plant (3) the conditions of storage during the holding time, especially whether these involve cold storage.

Large American producers of Aloe vera have done work monitoring the changes in biological activity with time and holding conditions. They have shown that there is significant loss of activity if the cut leaves are kept at ambient temperature for more than 6 hours after harvest and that if the leaves are kept beyond that time, then the level of activity goes on falling and reaches zero after about 24 hours. They found that although cold storage slows the rate of loss of activity, it cannot prevent it altogether. All this means that the leaves, after being gathered from the field, should be transported into cold storage as quickly as possible, preferably well under the six hours required for deterioration to start, and should be kept cold. Processing should begin as soon as possible, i.e., holding times should always be minimized. Moreover, the processing should also be completed as quickly as possible. A guideline has been suggested that the overall time from cutting to the completion of processing should not exceed 36 hours, even when cold storage is employed. Obviously, these criteria put certain pressures upon process operators. Meeting these criteria calls for well organised logistics and careful management and if these are not provided then standards can slip and product of a lower grade will be turned out. The deterioration which occurs will be partly through spontaneous decomposition but is has also been shown that in the cut leaf, upon standing, enzymes within the cut leaves remain active and start to reduce the concentration of active principles. Clearly then, a careless processor could quite easily completely destroy the biomedical activity of his Aloe before even starting to process it.

The Processing Sequence

As soon as processing starts, the leaf must be designated either for gel or for whole leaf extract. If it is for gel the leaf will be cut to dissect the central gel from the outer rind. This may be done either by hand cutting or by machinery. Obviously, the hand and mechanical versions of the process cannot be exactly the same. The machine extraction of the gel is bound to be just a little more "hit or miss" and as a result the gel extracted by this method usually contains rather more of the exudate materials (e.g. aloin), than hand dissected gel. If the leaf is to be for whole leaf extract, then it is ground up in a mill without any previous dissection. After these processes, the clear juice has yet to be obtained. In the case of the gel this involves only grinding gel tissue, which then disintegrates to yield mostly fluid with a little fibre floating in it. The gel is of such a high water content that it converts mainly into liquid. Some manufacturers remove the floating fibre, but others do not, since it contains some of the activity of the original gel and might as well be consumed with the liquid. In the case of the whole leaf, the extract has to be expressed from the mass of fibrous leaf fragments under pressure. This is actually quite hard to do because there is so much fibre relative to the quantity of free liquid available. Thereafter the extract must be passed on to a chiller to reduce its temperature.

Leaf Breakdown and Cellulase Enzyme

The process of disintegrating the whole leaf has to be watched quite closely. Firstly, in a poorly controlled operation it would be easy for the milling to raise the temperature significantly. The Aloe leaf is tough and fibrous. Plenty of energy has to be used to break it down to fine fragments. Such mechanical energy becomes dissipated as heat. Secondly, the separation of the liquid extract from the pulp, because there is so much fibre, is almost impossible unless a processing aid is added. The processing aid is the enzyme cellulase, which is capable of breaking down some of the cellulose fibre, and this makes separation of the liquid a great deal easier. There is a price to be paid, however, because the cellulase is also capable of breaking down the glucomannan constituent of Aloe which is such a key active principle for its biological activity. As to whether or not any detrimental breakdown of valuable glucomannan occurs, is dependent upon the length of time for which the Aloe is exposed to the effects of active cellulase and the amount of cellulase enzyme used. If excess cellulase is used, or if the active enzyme is left too long in contact with the Aloe, then very detrimental breakdown of the glucomannan may occur. Once again it is a matter of controlling carefully the time and conditions of contact between the Aloe and the enzyme. The cellulase should not be regarded as being inevitably harmful, for it is not. The glucomannan, as was stated above, occurs in different versions, and any sample of Aloe will contain a cross-section of glucomannans having different molecular weights (for the non chemist, this can be regarded as being much the same as molecules of different sizes). The cellulase can convert some of the large glucomannan molecules into rather smaller ones. This may actually improve some of the biomedical properties of Aloe - because the glucomannan of different molecular sizes have different biological activities. However, clearly, if the process of degradation by cellulase were permitted to go too far, the effects would be wholly detrimental as all biological activity would eventually be destroyed by the continuing action of the enzyme. Once again, here, we are looking at a good process which is potentially liable to abuse by the ill-informed or careless operator. By using too much cellulase in his enthusiasm to make the separation stage easier, and by leaving the enzyme in contact for too long, he could well ruin his product completely so far as its biomedical activities are concerned. Note, though, that this would nonetheless still be an honest Aloe product in the sense that it would be composed wholly of Aloe with no dilution or adulteration. This processor's sin would be carelessness or ignorance rather than fraud. Nonetheless, the purchaser is going to be the loser, that is certain.

Management Will and Process Know-how

Please note that since it is possible for a processor to make such grave errors that would ruin the product, either pre-processing errors or processing errors, the number of times that these errors are made to a milder degree is likely to be considerable. If that happens, it would most probably have the effect of reducing biomedical activity rather than extinguishing it altogether. It really does seem reasonable to expect that the industry is likely to be making these lesser errors quite often in those plants which are subject to fairly poor process or quality control, resulting in delivery to the consumer of less than what he or she is paying for. Only the technically aware companies that also have good laboratory capabilities are likely to be in a position to meet all the known processing criteria. Obviously they also require to have the management will and ability to do so, bearing in mind that standards are always inclined to slip a bit unless watched and safeguarded very carefully from the top of the business by people who are also prepared to allocate the resources necessary to both attain and maintain high standards.

Carbon Filtration

Moving on now to further processing of the separated liquids, the whole leaf extract needs to pass through a filtration stage employing activated charcoal (carbon filtration stage). This is needed because the whole leaf extract unavoidably contains the materials of the Aloe exudate fraction - the fraction which contains the phenols, such as the laxative anthraquinone substance "aloin". This fraction must be substantially removed to avoid having a product with bitter taste and laxative action. Passing through the carbon filter does this most effectively. Users of Aloe can usually be fairly confident that whole leaf extract, as opposed to the gel, will have had the exudate fraction effectively removed, reducing its concentration in the product to only trace. The gel has a naturally low level of these anthraquinones - low enough that they will never cause a laxative effect. For that reason producers of gel products may or may not decide to carbon filter their material. As a result, it is more possible that one may buy a gel product containing perceptible anthraquinone components, than from a whole leaf extract.

This technology of carbon filtration permits Aloe whole leaf extract to be used, whereas that would not be possible without the carbon filtration step. It would be precluded altogether by the unacceptably high levels of anthraquinones and related compounds in the unfiltered extract. This explains why historically most of the market for Aloe juices has been satisfied until now with the fluid from the gel. As noted above, the gel dissected by hand is more aloin-free than that which is pressed out by mechanical means because the dissection is more exact and it is easier to avoid contamination with the fluid exuding from the rind.

So far as the carbon filtration stage is concerned in the processing of whole leaf, the reader will readily perceive that it is entirely unavoidable, but it does have a price attached to it in term of some loss of activity. Initially, the whole leaf extract has a wonderfully high level of biological activity compared to the gel (assuming that all the processing criteria have been well observed to this point). It also has a high solids concentration compared to gel. It is always surprising to anyone new to the field, that the concentration of soluble solids in Aloe vera gel is only 0.5 - 0.6%. This reflects the fact that this plant is a succulent well adapted to living in fairly arid places. Its adaptation consists of storing great amounts of water in its tissues. All its tissues are adapted to this function, but the gel most particularly so, and hence it consists mainly of water. However, the whole leaf extract contains from 1.0 to 2.0% solids. Typically the level of solids it contains is about two and a half to three times higher than the gel. Not surprisingly, the whole leaf extract, when processed according to good criteria, offers more of the all-important biomedical activity than does the gel, sometimes almost twice as much. Naturally, its activity level does not usually rise quite as much as its solids level compared to the gel. It appears that by making the whole leaf extract, one obtains a certain yield of active principles from the rind part of the leaf. This extra activity gained is not quite so high on an "activity per gram" basis because the rind also contains some inactive materials. However, it is more in absolute terms. The conditions of carbon filtration must be watched very carefully, however, since carbon filtration always reduces biomedical activity by at least a little. The filtered extract is therefore rather less strong biomedically than it was before filtration. Since one has no choice about doing the filtration step, this loss must be accepted. However, it should be minimized by observing carefully process controls over the filtration operation. So this is another area in which the unalert or careless processor can lose the Aloe's activity. There continues to be a certain debate within the industry as to whether gel or whole leaf extract is better. Often the gel is favoured just out of long habit or because people have the affection for it as the material of tradition, or the material they have always worked with. Sometimes people favour gel because they have had experience only with poorly processed whole leaf extracts. However, this author interprets the evidence shown to him by the Industry as clearly indicating the higher biomedical activity of the whole leaf extract when the correct processing parameters are applied. That does not mean that the gel is easy to process, that too is subject to the vulnerability of its active principles - for they are - substantially the same active principles.

Pasteurization

After carbon filtration, the whole leaf extract is passed on to be Pasteurized. So is the gel after its milling stage. This involves heating to 65 degrees Centigrade for 15 minutes or to rather higher temperatures for much shorter times. Whilst heating the extracts at all is undesirable, the Pasteurization cannot be avoided. Aloe gel or whole leaf extract, more or less free from aloin, is not itself able to kill bacteria or inhibit their growth. For marketing and distribution these products need to be protected from growth of bacteria and yeasts. This is done by a combination of two steps, the Pasteurizing process and the addition of preservatives (referred to as "sanitizers" in America), of which potassium sorbate is the commonest example. This Pasteurizing is not significantly harmful to the product so long as the proper process parameters are observed. What is perhaps much less desirable is the tendency for some operators to Pasteurize some of the product more than once. This, basically, is the result of carelessness, or incorrect management of particular batches. This occurs when, once the Pasteurizing has been carried out, the extract again becomes infected with high numbers of micro-organisms which multiply out of control. It is only likely to happen when a batch, once Pasteurized, is allowed to stand too long or under poor conditions. Obviously, one can accept that the heat treatment involved in Pasteurizing is inherently less than desirable. However, when it is done twice, obviously any damage to the product is multiplied. It is not only damage from the repeated heat exposure, but also the destructive effects of the bacteria while they are being allowed to grow. Sloppy, poorly supervised working conditions foster this kind of error and it really needs to be controlled and stopped.

Once the Pasteurizing has been done, the product is ready to go forward as finished product. This will be finished product of a type called "one to one". That means that its concentration is the natural concentration for the particular product. If the product is gel, it will go forward at this stage at a solids concentration of only 0.5 to 0.6%. If it is whole leaf extract, the solids concentration will be 1.0 or 2.0%. Sometimes this expression "one to one" can lead to confusion in the Industry. For example, a producer of unconcentrated whole leaf extract at a solids content of 1.5% may decide to call the product "3 to 1" on the basis that in terms of solids it is three times stronger than a gel. It really is not correct practice to do that because its activity, although higher than that of a gel will not be three times higher. In any case, the proper designation for such a product is really a "1 to 1 whole leaf extract" because that is what it is, and its chemical components are qualitatively different from those of a "3 to 1" gel. This will be discussed further in Issue 11.

Concentration by Evaporation

If the intention is to prepare a concentrate, either of gel or whole leaf extract, the "1 to 1" material is fed to an evaporator. A concentrate can easily be prepared using quite low evaporator temperatures. However, the more concentrated the liquid is to become, the more heat will be needed to bring about that level of concentration in the evaporator. A "40 to 1" concentrate of gel should have a solids concentration of 20% and a "40 to 1" concentrate of whole leaf extract will be really strong and should be from 40% to 80% solids. This seems to be taking the concentration step too far.

The first reason for this is real concern that the evaporator temperature will go too high and damage the biomedical properties of the Aloe. In fact, the temptation is constantly there during the concentrating of Aloe in the evaporation, to let the temperature go too high. The higher the temperature goes, the faster the process goes and the lower will be the costs of the operation. Indeed, keeping the evaporator temperature down, as is needed to optimize the product, will also limit the processing capacity of the plant. If there is much material waiting to be processed, that will impose an understandable pressure upon the production manager. Almost inevitably some production managers will yield to the obvious temptation. The higher the final concentration of the Aloe solids, the higher the evaporator's working temperature will have to go to perform the necessary degree of evaporation within an economic time-scale.

The second reason why high concentrates are undesirable is that the sensitive biomedically active carbohydrates are damaged not only by heat but also by increasing concentrations of mineral salts. Aloe contains mineral salts which represent a significant proportion of its dry matter. As the extracts are concentrated, the salts reach higher and higher concentrations, causing progressively greater damage to the glucomannans. Given the content of metal ions in the product at its natural strength, as about 20% of total solids, and allowing for the presence also of non-metal ions such as phosphate, the salts concentration in 40 to 1 Aloe Gel could be of the order of 6-7% and in 40 to 1 Whole Leaf Extract could be as much as 20%. These concentrations produce very high ionic strength which can certainly alter the molecular properties of the Aloe Glucomannan.

Spray-Drying and Freeze-Drying

The final processing stage, which may or may not be applied is drying. This author regards the drying step as inherently undesirable and thinks it should never be used at all unless it is for an application which can only use dry material. In making dried product, it is an economic necessity to concentrate the product maximally in the evaporator before drying, with all the damage which that entails. Then the drying process itself will add its own quantum of further damage to biological activity. If the drying process applied is spray-drying, then we have maximum heat application during the drying and hence maximum damage. Moreover, the spray drying step often requires the addition of a processing aid - usually maltodextrin - that cheap extender from corn starch - which may or may not be declared as an ingredient on the product label.

The best way of drying is freeze drying, because the product is spared in this way from high heat. However, it is still true that maximum evaporation has to be applied first. The best product which can be obtained at all in a dry condition is a freeze-dried product prepared directly from a "1 to 1" extract without evaporation. However, no such product is likely ever to be offered on the market since the drying costs on this basis simply could not be born. Consumers in the U.K. and Europe, taking supplies of Aloe from U.S.A. and Mexico, or from Australasia, will often find, if they enquire deeply enough, that they are buying dried product (perhaps even spray-dried product) which has been shipped dry to save freight costs and then reconstituted with added water, back to a "1 to 1" or to a concentrate strength. The consumer can thus be deeply deceived, because there is no comparison between a fresh "1 to 1" extract or, say, a "2 to 1" or 10 to 1 concentrate, and a product which has been completely dehydrated and then re-constituted, especially if the drying method was spray-drying.

Conclusion

It is obvious that an honest but incompetent processor of Aloe could easily produce a genuinely 100% Aloe which would be devoid of biomedical activity. This would happen through either ignorance or a lack of attention to detail in the processing operations. Is the consumer getting what he or she wants in such a case? In terms of getting pure 100% Aloe the answer is obviously "yes". In terms of buying biomedical activity, viz., the potential to cure or alleviate illnesses, equally obviously the answer is "no". In the ultimate case, the consumer is actually getting nothing worthwhile for the money at all - no more than if the supplier were putting pure water into the bottle and passing it off as Aloe.

Is it likely that the Industry is widely peopled with such incompetent and ignorant suppliers? The answer to that is "no". This writer feels sure that few go so far as to entirely inactivate previously active product. Is it likely that the Industry is widely peopled with suppliers who, through ignorance and somewhat substandard competence, partially inactivate their Aloe through avoidable errors? The answer to that, this author thinks, is "yes". It is almost bound to be the case because there is no authority responsible for monitoring and policing this situation. Bio-assays (i.e. biological measurements of activity) are available for (1) the anti-inflammatory effect, (2) the healing effect and (3) the immunostimulant effect. They could all be monitored by these available bio-assays. Yet that is not the accepted way of controlling Aloe. Individual companies, if they are big enough and sophisticated enough, have the means of monitoring these activities in their products, but it is entirely up to them whether they do it or not. To whatever extent they are doing it, this is just for their own information. There is no requirement for them to publish the results. Even less is there any requirement for them to use these bio-assays as quality control procedures and to reject batches which fail to come up to a certain standard in respect of biological activities. Hence there is absolutely no guarantee for the consumer that the products he or she will buy will possess the highly desirable biological activities that are reported in the scientific and medical literature as belonging to Aloe, nor that they will attain a certain minimum value in respect of these biological activities.

This situation is obviously completely unsatisfactory. The work of the International Aloe Science Council based in Dallas, Texas, is laudable. They will provide Certification of products as being genuine Aloe. However, whilst one should give them every credit for seeking to upgrade their criteria for the genuineness of Aloe, the present criteria leave much to be desired. They depend upon certain convenient marker substances which Aloe contains, such as, for example, calcium and malic acid. These requirements gloss over the fact that calcium and malic acid have no role whatsoever in providing the biological activities of Aloe and are merely "incidental" components. Moreover, the determined fraudster could easily add either calcium or malic acid to his product to make it look genuine when it is not. These additives would be extremely cheap to add. Since they carry no biological activity of the kinds we look for in Aloe, it would still be a fraudulent product with either zero or a much reduced biological activity. Moreover, the Certification from the Aloe Science Council does not guarantee that the product is 100% Aloe or anything like it. Products with only 15% or 20% Aloe may gain certification.

It is obviously an urgent matter to have in-plant quality control based upon biological activity, certification based only upon biological activity and, indeed, random testing of products on the supplier's shelf, based upon biological activity. Until this happens, the buyer's only protection is to buy from a supplier whom he or she trusts to thoroughly research the origins of his product in the producing country, to independently monitor processing there and to provide good storage and distribution, free from dilution and adulteration at all times. Those buyers in the U.K. and Europe who are not multinationals with their own plantations, can be doubly at risk because their national suppliers are themselves dependent upon overseas producers and middlemen whom they cannot easily control. These buyers can be secure, however, provided they fully check out their complete line of supply and the validity of the production processes. And one should not assume either, that multinationals are necessarily free from wrong practices, just because they are multinational. Adherence to truly good practices requires the commitment of management from the top down in such organisations.