Varietal juices were produced from 11 apple cultivara from three apple-growing regions of Ontario before and after cold storage in two consecutive crop years. Juices were analyzed for individual sugars using HPLC. The ranges of concentrations (grams per 100 mL) found for juice produced from fresh and stored fruit, respectively, were as follows: sucrose 1.

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The quantity of fructose, glucose, and sucrose present in authentic varietal grape juices produced by cold and/or hot pressing from 56 cultivars was determined by liquid chromatography for the 1988 and 1989 seasons. The concentration of fructose, glucose, and sucrose and the fructose:glucose ratio ranged from 5.97 to 10.92, 4.91 to 9.99, trace to 1.04 g/100 mL, and 0.92 to 1.41, respectively. Sorbitol and hydroxymethylfurfural were not detected in the authentic grape juices. Genotype had no significant effect on the fructose and glucose contents. The labrusca-type cultivar group was significantly higher in the sucrose concentration and fructose.glucose ratio than either the vinifera or the French hybrid groups. The pressing method had no significant effect on the sugar composition. The glucose, fructose, total sugar, and total soluble solids contents were significantly higher in the juices from the warmer and sunnier 1988 season. The total sugar contents correlated highly with total soluble solids, but the latter averaged 1.81 units more than the former. Most commercial grape juices had a composition similar to that of the authentic juices, except that they had only traces of sucrose. Also, most commercial grape juices contained measurable quantities of ethanol, glycerol, and hydroxymethylfurfural.

Quantities were determined of tartaric, malic, citric, lactic, succinic, and shikimic acid present in juices produced by cold and hot pressing from 56 grape cultivars grown in Ontario for the 1988 and 1989 seasons. The individual acids were separated by liquid chromatography (LC) and detected at 210 or 250 nm. Lactic and succinic acids were determined enzymatically. The ranges of acid concentrations found were as follows: tartaric, 4.19-13.51 g/L; malic, 1.68-15.36 g/L; citric, 0.305-1.158 g/L; lactic, 0.015-0.388 g/L; succinic, 0.002-0.075 g/L; and shikimic, 0-0.102 g/L. Tartaric and malic acids were the major acids in every cultivar. The tartaric:malic acid ratio ranged from 0.52 to 4.36, but it was >1.0 in most cases. Genotype had significant effect only on the shikimic acid content. Hot pressing of red cultivars yielded juice with significantly higher pH and tartaric, citric, lactic, and total acid contents than cold pressing. Vintage had no significant effect on acid composition. The total acid content determined by LC was always considerably higher than the titratable acidity, but good correlation existed between the 2 measurements. Most commercial grape juice had similar composition to that of authentic juices. However, tartaric acid content was lower in the majority of commercial juices because of losses during the detartration process. Also, indications of acidulation existed in some of the commercial juices.