Notes a The identity of the material and its manufacturer can be obtained by contacting the International Aloe Science Council, Irving, TX.
b Determined at Inchcape Testing Services according to IASC proceedure by inductivity-coupled plasma atomic emission spectroscopy. Data expressed are concentrations in mg per liter of a 0.62 mg/ml solids solutions.
c Conductivity of a 0.62 g/dl solution at ambient laboratory temperature. Test conducted at Inchcape Testing Service.
d Conducted according to the IASC protocol. Malic acid data is expressed as a percentage of the ARF Standard Sample currently in use at time of testing. Test conducted at Inchcape Testing Service.
e Assay conducted at Inchcape Testing Service on 500 mg of sample using the published method (Pelley etal., 1993). Values expressed are the % of solids that are alcohol precipitable hexose.
f Alcohol Precipitable Solids. This is the mass of solid precipitated from the 500 mg sample at Inchcape Testing Service determined by lyophilization at UTMB. Data expressed are percentage of precipitated dry mass versus the 500 mg of powder originally tested.
g Lyophilized, alcohol precipitates were exhaustively dialysed. Data expressed are the percentage of retained material verus the 500 mg of powder originally precipitated.
h Retained material was hydrolysed in 6N constant boiling HCl for 10 to 20 minutes at 120 °C. After neutralization, ratio of monosaccharides determined by HPLC on a Dionex PA-1 column with a pulsed amphoteric detector. Data expressed are percentages of individual sugars versus the total sugars identified on HPLC.
i Unusual sugars were identified. Sample 6 was 74% amino sugars; sample 8 was 15.5% fructose; sample 9 was 28.1% fructose; sample 10 was 9.7% fructose. Adapted from Pelley et al. (1998) with permission.
realized that conductivity of 1:1 gel provided a quick spot test for dilutional adulteration. An anecdote from c.1995 (the late Al Davis) stated that diluted feed stocks had low conductivity. At the time we were developing the ARF Standard Samples, Wang was measuring the four major cations in A. barbadensis gel. We quickly realized that although individual cations varied greatly, the sum of the cations were remarkably consistent (Pelley etal., 1993). Since conductivity measures the sum of all the ions, it was appreciated that it could provide a cheap and rapid substitute for analysis of the individual ions (Pelley etal., 1993), although it could not replace measurement of individual divalent cations for certification. Since then measurement of conductivity has proved useful in screening for fraudulent 'aloe' (Pelley etal., 1998). Figure 8.12 below illustrates that there is a good correlation between the simple sum of the four Texas A&M analytes and conductivity for the ten samples examined immediately above.
Inspection of Tables 8.10 to 8.12 reveals the utility of conductivity in screening samples alleged to be aloe. Economically, the biggest adulteration/fraud problem is the substitution of maltodextrin for freeze-dried or spray-dried aloe (Tables 8.11 and 8.12). This is one of the areas where a quick conductivity spot test can be extremely useful. There are 11 samples of commercial material consistent with authentic aloe in Tables 8.9 and 8.12 (8.11: 2, 3, 5, 6; 12A: 1-7). Ten of these 11 are within the one a level (1,528mS calculated from Table 8.4) and the 11th is within the 2a level (1,026mS calculated from Table 8.4). At the opposite end of the spectrum were the 12 commercial samples consisting almost entirely of maltodextrin (Table 8.11: 8-10; Table 12B: 8-16). Ten of the twelve were beyond the 3a limit (524mS calculated from Table 8.4) and two (Table 8.11: 8-10; Table 12B: 8-16) approached the 3a limit. Last are the commercial materials that appear chemically to be spray-dried aloe but whose label clearly claims them to be freeze-dried aloe (Table 12C: 17-19). These all yielded conductivity results exactly consistent with spray-dried aloe, that is a conductivity one-half that
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