Excerpts By Ivan E. Danhof, M.D., Ph.D.

 

In the evolution of processing methods of Aloe vera leaves, The hand-filleting procedure  was developed to avoid contamination of the internal gel fillet with the yellow sap found  in the pericyclic cells of the vascular bundles located just beneath the thick green rind of  the leaf. The yellow sap has a number of laxative anthraquinones, the major being aloin.

As the laxative action of these anthraquinones may be associated with considerable  abdominal cramping in humans, these agents, although widely used from the 17th  through the 20th centuries, have been replaced by laxative agents possessing fewer  undesirable side-effects.

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Aloin contains a glucose molecule attached to the parent anthracane ring. If the glucose  is cleaved off, the resulting product is Aloe-emodin, which has, depending on its  concentration, a red through brown through black coloration, which is in cosmetic  products. Thus, the presence of aloin or its derivatives is undesirable both for internal  consumption and topical usage.

Only recently have processing methods using the entire whole leaf been perfected  so the undesirable elements can be selectively removed, while maximizing the  desired constituents. Among the desirable constituents are the polysaccharides  (glucomannans), glycoproteins and  associated growth factors.

 

In Table I, the data reveals that the  quantity of desirable polysaccharides is  2 1/2 to 3 times the yield using the  hand filleting methods.

 

 

 

 

 

 

 

 

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Occasionally an individual sample  may contain more than the amounts indicated in the table; this may occur if the leaves are dehydrated. These ranges will  encompass 95% of routine samples based on current in-hand data.

The major undesirable constituents, the polyhydroxyanthraquinones, can be selectively  removed through filtration through charcoal and other absorbents so the remaining level  of aloin is 1 ppm or less.

Table II data compares various processing  methods and the effect on yield (total  solids), aloin concentration, and the  distribution of sizes of constituents. The  whole leaf method can produce an Aloe  juice which is high in total solids, high in  retained high dalton (molecular weight)  polysaccharides with their scientifically  demonstrated benefits, while the aloin  concentration is at a very acceptable low  level.

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Cold Versus Heat Processing Methods  

Data suggest that the time interval between leaf harvesting and processing (sun  exposure) should be minimized (less than 24 hrs); heat exposure during processing  should be minimized, especially if high temperatures are maintained for an hour or more.

In the cold processing technique, the entire processing steps are accomplished without the application of the heat. Coats () reported the use of enzymes, like glucose oxidase and catalase to inhibit the growth of aerobic organisms within aloe vera gel and thereby sterilizing it. Other sterilization steps reported in the cold processing include exposing the gel to ultraviolet light followed by micron filtration (Maret ). (1)

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Advantages Of The Whole Leaf Cold Processing  Methods  

Advantages of the whole leaf, cold-processed, approaches include the following:

  1. Maximizes the yield of desirable constituents.
  2. Increases cost effectiveness of processing.
  3. Increased total solids concentration.
  4. Increased polysaccharide concentrations.
  5. Virtual absence of undesirable anthraquinones.
  6. Improved desirable characteristics for cosmetic usage.
  7. Increased concentration in permeability factors increasing transdermal  penetration.
  8. Improved taste palatability.
  9. Increased concentration of growth factors responsible for accelerating of healing.  10. Increased concentration of factors responsible for the stimulation of the immune  system.

 

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REFERENCES
  1. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3551117/