Paper chromatography of the anthocyanidins, the phenolic components of the anthocyanins, is the most satisfactory means of detecting adulteration of Concord grape juice with other red grape juice and colored Italian grape skin extract. The 5 aniliocyanidins found in grape colors can be readily separated into 3 spots by paper chromatography. In the proposed method, anthocyanins are separated by lead precipitation, dissolved in water, and acid-hydrolyzed to obtain the anthocyanidins. Thirty Concord samples, 7 red grape juice samples, and 5 Italian grape skin extracts were examined and results were good. Four unknown samples were analyzed by 5 collaborators; all collaborators correctly detected the adulterated sample and the pure Concord sample. This method was recommended for adoption as official, first action
A second collaborative study of this method has been made with 5 samples. No difficulties were experienced with the method, and the results were satisfactory. While a few collaborators failed to detect adulteration in some of the samples, no collaborators judged satisfactory samples as adulterated. Collaborators agree that the method is simple and provides more information than the single dimension paper chromatography test in many cases. The 2-dimension method has been recommended for adoption as official, final action.
Previous methods for estimating vanillin and ethyl vanillin in mixtures were long and complicated. However, this paper presents a simple chromatographic separation and quantitative determination of these aromatics, using Mitchell equipment for paper chromatography and 8 × 8” papers. Development for 2 hours separates the compounds adequately; they are then extracted and measured by absorbances at 348 mμ in alkaline solution. Recoveries of added vanillin and ethyl vanillin to vanilla extract are excellent. Aside from normal manipulative errors, the only significant inaccuracy is caused by the small amount of natural p-hy-droxybenzaldehyde in vanilla (usually equivalent to about 5% of the vanillin content). The method does not separate p-hydroxybenzaldehyde and vanillin. Total errors in the method do not exceed 0.01%. Comparison of the method with the two AOAC methods for vanillin shows that the paper chromatographic method gives results close to those by the ultraviolet absorption method, in most cases, and significantly lower results than the photometric method, which is known to give erroneously high results.
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