The first quality control parameters used in the aloe industry were the determination of solids and quantitation of calcium and magnesium. The use of solids is obvious and traditional in the plant juice industry. Over 20 years ago it was appreciated that aloe juice was comparatively rich in calcium and magnesium (Waller etal, 1978). Solids are readily determined by simply evaporating at elevated temperature (e.g. 105 °C) to constant weight. If a single analytical test is performed in a processing facility, it is usually for solids. Divalent metal cations, on the other hand, are more complicated to determine, usually by inductively-coupled plasma atomic emission spectroscopy. Although other methods (e.g. ion selective electrodes) could be used for process control, spectroscopy remains the method preferred for IASC certification because of the lack of interference. Subsequent to the Texas A&M study, the monovalent cations have been added to the analytical armamentarium because there is little additional cost to adding K and Na , once Ca and Mg have been specified.
In general, neither solids nor the content of metallic cations change during processing. If the solids content of the depulped gel is 0.58 g/dl than the pasteurized, decolorized gel is likely to have a solids content of 0.58g%. This does not mean that there are no losses during processing, but that these losses are of the spillage variety and do not decrease the solids content. On the other hand, final processing involving concentration will radically alter solids content. That is the purpose of evaporative concentration, freeze-drying or spray-drying. As discussed above, the idiosyncratic nomenclature of the aloe industry frequently confuses those not intimately familiar with its less-than-logical reasoning (e.g. '100X' is not 100% pure aloe, which is '200X'). Similarly, enzymatic treatment, heat treatment and treatment with activated charcoal should not remove basic chemical components like mineral salts. The one exception to this may occur during storage, particularly cold storage of '40X' liquid concentrates. An insoluble complex may form between the divalent cations and the divalent organic acids, especially when oxalic acid is present, which then precipitates, removing the calcium from solution. When this precipitate is primarily calcium oxalate, it can be impossible to dissolve unless the pH drops to below 3. On occasion, even calcium malate can be difficult to dissolve. In summary, the solids and metal cations, although not linked to biological activity, are desirable because of their extreme stability; multiparameter deviation of these materials strongly implies dilution or non-ionic adulteration.
Table 8.10 illustrates typical findings of solids content in 13 commercial liquids alleged to be 'Aloe vera.' These liquids were divided, based on multiparameter analysis (Pelley etal., 1998) into two groups corresponding to Samples 1—7, consistent with authentic A. barbadensis extracts and Samples 8—13 not consistent with A. barbadensis. None of the liquid samples 1—7 had the exact solids content predicted from the label claim, although all fell within the range of acceptability for IASC certification (Table 8.3). As a group their average came close, the absolute deviation expected was only 19%. This degree of variability is consistent with the variability observed in the Texas A&M study (Table 8.2). On the other hand, with samples 8—13, multiparameter analysis indicated a high suspicion of fraud. The solids content of these were different from the label claim (47% discrepancy ) and 75% were outside of the IASC certification range (Table 8.3).
As discussed above a sizable discrepancy between the IASC cation distribution and a tested population also raises the possibility of fraud. Table 8.11 illustrates cation values in three groups of commercial materials: (i) those consistent by multiparameter analysis with ARF Process A. barbadensis gel (#1—3); (ii) those consistent by multiparameter analysis with WLE (#4—6); and, (iii) those consistent with maltodextrin being fraudulently sold as A. barbadensis material (#7—10). By reference to the IASC distribution for cations (Table 8.3) all of the ARF Standards and the materials consistent with aloe by multiparameter analysis were within the range of acceptability for calcium and magnesium content. On the other hand, authentic maltodextrin and materials consistent with maltodextrin fell outside the limits of acceptability for IASC certification and as a group were ten times the SEM removed from any of the calcium and magnesium populations in the Texas A&M study (Table 8.2). Thus, just as with the solids content, the abnormal content of mineral cations strongly suggests that the material under consideration is either fraudulent (Table 8.11, 8 and 9) and or so extensively adulterated as to be no longer recognizable as aloe (Table 8.11, 10).
Very few aloe producers or consumer product manufacturers possess an atomic emission spectrophotometer, so these determinations are usually sent out to an independent testing laboratory. Therefore there is frequently a need for a cheap and rapid test to substitute for the measurement of the individual cations. Around the mid 1980s it was
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