Grape juice, adulteration

In 1887 G. A. Crampton of the United States Department of Agriculture examined 36 samples of wine from different parts of the country and found boric acid in all but two of them. Hesitating to believe that adulteration could be such a universal practice, he analyzed many specimens of natural grape juice and found that boric acid is a natural con-... 

Phenolic compounds have sometimes been used to detect adulterations of fruit juices and jams. Most of them are flavonols, but some HCA derivatives can be used since they are typical of some fruit species such as tartaric derivatives in grape. For example, grape juice can be detected by the presence of caffeoyl-, / -coumaroyl-, and feruloyl-tartaric acids, whereas the presence of quinic esters of HCA would imply adulteration with other fruits. A method has also been developed for detection and quantitation of pulpwash, a lower-quality juice product, in orange juice [9] feruloyl and sinapoyl glucose, in addition to different other phenolic compounds, were present in much larger amounts in pulpwash. 

To detect adulteration of wine. Bums et al. (2002) found that the ratios of acetylated to p-coumaroylated conjugates of nine characteristic anthocyanins served as useful parameters to determine grape cultivars for a type of wine. Our laboratory utilized mid-infrared spectroscopy combined with multivariate analysis to provide spectral signature profiles that allowed the chemically based classification of antho-cyanin-containing fruits juices and produced distinctive and reproducible chemical fingerprints, making it possible to discriminate different juices. " This new application of ATR-FTIR to detect adulteration in anthocyanin-containing juices and foods may be an effective and efficient method for manufacturers to assure product quality and authenticity. 

Table II shows that sucrose levels are highest in peach fruit and very low in blackberry, cherry, and grape. The % C.V. for sucrose content for many of the fruit samples is extremely high, most likely because of enzymic or chemical hydrolysis. The average sucrose content of plum fruit is 38 of total sugars, while processed plums contain only 1. Presence of large quantities of sucrose in prune juice has, in fact, been used as an indication of adulteration ( ). Cherries and grapes contain invertase Cllj 12) which may account for sucrose not being detected in some samples and may also explain the high % C.V. for those fruits. In examining apple Juice concentrates, we did not detect sucrose in seven-fold concentrates whereas we did in fo ar-fold apple concentrates (7.) > the time-temperature conditions allowing for complete hydrolysis in the more concentrated product.

Wine was analyzed by Hughes and Johnson (1983) and carbohydrates and alcohols were determined. Cation-exchange chromatography with a water mobile phase was used for the separation, and postcolumn addition of NaOH was necessary for PAD detection. Both dry and sweet wines were analyzed, and as expected, the dry wine had much less fructose and dextrose than the sweet wine. A peak for sorbitol was not observed for any of the wines tested. Because sorbitol is not naturally present in grapes, its presence in wine would indicate adulteration of the wine with other fruit juices. 

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