The word Aloe has two different meanings - One is an invented term that refers to the generic name of the Asphodelaceace subfamily. The second one is used to refer to pharmaceutical products obtained from the juice of certain Aloe species.
The true aloe, lat. Aloe Vera, belongs to the subfamily of Asphodeloideae (Affodilaceae) and further to the family of Xanthorrhoeaceae. The genus of Aloe plants includes more than 250 species, although only a few are used for commercial cultivation. They are water-storing xerophytes adapted to warm desert regions where water is scarce. Like the agave plants, the aloe plant belongs to the succulents (sap-rich plants). Its growth habit resembles a hybrid of shrub, herb and tree. Its fleshy, leathery leaves are usually toothed and often end with a spiny tip. The leaves can grow 50 cm long and without or with a small stem in dense groups (rosette-like growth habit). Their height can be up to 3 meters, although a lower height is preferred in plantation cultivation.
The anatomy of the leaves is decisive for the respective intended use: for example, different parts of the leaf are required in the pharmaceutical industry other than in the cosmetic industry. Roughly, the leaf is divided into two parts: The leaf bark with the underlying latex layer and the leaf gel. Each area contains specific chemical substances that can be used for different purposes. For example, the pharmaceutical industry is increasingly targeting the leaf bark and latex layer. The anthranoids contained there, a chemical class of substances, is suitable for medicinal applications and should never be included in cosmetic products. Careful selection of the right plants with appropriate processing procedures is therefore very important. Only the aloe gel obtained from the aqueous leaf gel/pith is used in cosmetics.
The exact origin of the plant is unknown but an origin in Africa is suspected. Its good adaptability to dry areas allows its cultivation in almost all tropical and subtropical regions worldwide. The plant prefers low annual precipitation combined with high average temperature around 23 degrees Celsius. Main cultivation areas are found in the USA, Mexico, Africa and the Mediterranean region. There, the plants are cultivated in plantations, although wild collections can also be found. Depending on the quality requirements, locations with high sunlight and good soils can be advantageous: these include small farms in Greece, Spain and the Canary Islands in particular. After two to three years, the plant forms yellow and red flowers.
Three to four years old leaves are harvested from the outside to the inside. For this purpose, the mature leaves are separated individually by hand at the base. Since it immediatley leaks anthranoid-containing sap from the base, a certain amount of time should be waited for this leaking process to be completed before further processing (see below).
Aloe vera gel occupies a position between the classical mucilages or mucilage drugs and gums (e.g. gum arabic). Before obtaining the powder, the gel must be obtained and prepared.
Aloe gel is a colorless mucilage obtained from the anthranoid-free parenchymatic tissues (=peeled leaves). This gel consists of almost 95% water and contains, among other things, chemical agents such as glucomannans, glycoproteins and aloeins. Due to the high water content, microbial decay occurs very quickly, making chemical preservation, stabilization or thermal preservation is necessary.
The leaf consists of the leaf bark with the spines and the characteristic prickle, the latex layer and the leaf gel. The main component is the hydrous pith with the characteristic mucilaginous, transparent gel.
In order to reduce dirt and possible impurities on the outside of the leaf, the leaves are washed (mechanically) after harvesting for subsequent processing. Due to the juice escaping directly after the plant is cut, a waiting period must be observed to reduce residual anthranoids in the leaves. Due to the increasing demand worldwide, four major production processes have been established: whole leaf, rolling, filleting and mechanical peeling.
As the name suggests, in the whole-leaf process the entire leaf is crushed and the obtained pulp is then pressed. All substances, including the unwanted anthranoids, are separated at the same time. In order not to have these substances in the final product, special activated carbon filters are used: these remove anthranoids, but also a large part of bioactive substances. This results in high quality substances but with (too) few ingredients. The advantage is an adjusted product that can be easily further processed and contains only a small amount of anthranoids.
The rolling process differs from the whole-sheet process only in the preparation of the leaves: in the rolling process, the sheet is first cut open on one side and then passed through a roller. Starting from the closed side of the leaf it is passed through the roller and the gel contained in the leaf flows out through the previously cut side. Since the undesirable anthraquinones are also extracted here, subsequent filtering must take place with the disadvantage/advantage mentioned above.
The filleting of the leaves is reminiscent of fish preparation: the leaves are cut open individually by hand in order to gently remove the leaf pulp or gel. Through clean cuts, the gel can thus be carefully removed from the leaf without damaging the anthraquinone-containing cells. Contamination can thus be greatly reduced. The "gel fillets" still need to be washed and can then be further processed (see below). After filleting is usually no need for further processing steps, which is why desirable bioactive substances remain in the gel. The quality of this process is therefore at its highest.
In the case of mechanical peeling, attempts are made to make the advantages of filleting even more efficient. For this purpose, the leaves are passed over a type of milling machine that mechanically removes the outer skin. Since the leaves have different sizes and characteristics, this can lead to increased anthranoid contamination. These substances still have to be removed with filters. The advantage is a qualitatively higher starting substance in relation to the whole-sheet process. The downstream treatment processes are thus more cost-effective.
The obtained gel is now preserved by a type of drying which can be carried out either by cold or by supplying thermal energy.
In spray drying, the thermal variant, the gel is exposed to a warm wind tunnel for a short time and under high pressure. Since only low temperatures are used, gentle drying takes place without destroying the gel. The powder produced has a longer shelf life and can be re-suspended depending on the indication.
Drying by freeze-drying is a particularly gentle form of preservation: the gel is slowly cooled until a solid frozen state is reached. Due to the presence of a vacuum and special temperature intervals (all below the freezing point), the water can pass directly from the ice state to the gaseous state: this is called sublimation. All the substances contained are trapped in the previously produced ice framework and have rarely been destroyed by ice crystals, what remains are usually pure initial substances that are preserved for a long time. The preservation is based on the absence of water which is needed by microorganisms to grow. Special packaging is used to prevent hygroscopic behavior, i.e. the absorption of moisture from the air. The high cost of equipment is reflected in the final price of the product.
Aloe vera gel consists largely of D-glucose and D-mannose built polysaccharides (55%) which allow a high concentration of water. In addition, freshly obtained gels contain simple sugars (17%), minerals (16%), vitamins (A, E, C), amino acids, proteins, and enzymes. These substances are often degraded by the manufacturing process, preservatives, or excessive storage. Aloe vera gel is believed to have anti-inflammatory, immune system stimulating, irritation reducing and wound healing effects. Drying by spray freeze-drying allows almost all original active ingredients to be preserved.
Aloe vera gel itself consists largely of D-glucose and D-mannose built polysaccharides (55%) which allow a high concentration of water. Freshly obtained gels contain simple sugars (17%), minerals (16%), vitamins (A, E, C), amino acids, proteins, and enzymes. These substances are often degraded by the manufacturing process, preservatives, or excessive storage. Aloe vera gel can have anti-inflammatory, immune system stimulating, irritation reducing and wound healing effects. Almost all original active ingredients can be preserved by spray freeze-drying.
Due to great media attention, the product is increasingly used internally in large quantities, although there is still no clear evidence. Several studies present here partly controversial substances which still have to be verified. Especially the plant origin, the starting material and the form of application hold a large part of interfering factors in these studies. The polysaccharides (soothing and immunostimulating) and glycoproteins (antiphlogistic effect) contained in the plant could have positive effects. The enzymes contained are also said to have an irritation-reducing effect: their activity can reduce inflammatory processes and thus lead to an immune-stimulating and wound-healing effect.
Increasingly, commercial products are also coming onto the market. These tonics or fitness drinks are offered in the form of juice, shakes, cocktails or shots and are made from the dried powders, among others. The advantages are longer shelf life, better dosing ability, individual product application (in shakes etc.) and higher quality raw materials. Special attention is paid in Aloe Vera products to the substance Acemannan, also called Aloverose. It is a (muco-) polysaccharide which can have immunostimulating, antiviral and antineoplastic effects. Often this substance serves as the marker for the quality of a gel. Aloverose content, similar to sugar content in grapes/fruit, reflects the ripeness of the leaves. A good Aloe Vera has about 800 mg /ltr Aloverose, very good products 1000, top juice brings it to 1200. It should be noted that you can not compare whole leaf juice with filleted quality. A whole leaf juice can easily bring it up to 2000 mg because the polysaccharides lie under the leaf skin and you can not extract them completely when filleting. It should be mentioned that a high proportion of aloverose is lost (up to 50%) through spray or freeze-drying processes. The reabsorption of water or fat (so-called suspension) decreases by up to 80%. Nevertheless, spray drying and freeze drying are the best forms of gentle preservation relative to concentration or chemical preservation. It should always be considered which gel was dried: the fresh gel or gel already processed with filters.
It is precisely the media presence that aloe products owe a great deal of hype to, which continues to this day: according to a study, 71% of the surveyed people attribute a particularly caring effect to aloe products. In general, the fresher the starting material and the less the preservation, the more attention must be paid to microbial contamination. Particularly in gentle drying, preservatives are often deliberately not added. A microbial check is therefore advisable.
Depending on the area of application, different concentrations are offered: the ratio of fresh plant to end product is important. A ratio of 200:1, for example, indicates that 200kg of starting material was processed to produce 1kg of end product. The preservatives contained are also important for the subsequent areas of application and should be in line with the product philosophy (e.g. no citric acid in cosmetics, as this can cause irritation to the skin). In general, the fresher the starting material and the less the preservation, the more attention must be paid to microbial contamination.
It is precisely the media presence that aloe products owe a great deal of hype which continues to this day: according to a study, 71% of the surveyed people questioned a particularly caring effect to aloe products.
The anthranoids, which are found in the leaf bark and underlying latex layer, have already been replaced by more controllable laxatives. The manufacturing process and the preparation steps are important in order to avoid having this substance class in cosmetic products. Several chemical markers have been introduced to detect the impurities, including the anthranoid aloin. If its content is too high, the product should not be ingested or applied (the BFARM recommends no more than 30mg of the substance per day, with a maximum application period of 2 weeks). Often customers try to prepare the leaves fresh (e.g. as a drink or to apply to the skin) and damage the latex layer when cutting it open. This results in the leakage of anthranoids onto the filleted gel. By experiments it was found that in extracted gels rinsed with water still higher amounts of aloin (factor 300) were ingested than in industrially produced products. Thus, only industrially manufactured or tested products should be used.
Aloe vera gel may take on a slight brown tint over time, as this is a natural aging process. This does not reduce the quality of the gels in the first place, but can be reduced by storing them away from light and in a cool place.