Chemical comparison of 100% apple, orange and grapefruit juices directly pressed and made from concentrate

English. One hundred per cent apple, orange and grapefruit juices were analysed for ascorbic acid (AA) content, total polyphenolic content (TPC), and other parameters: titratable acids (TA), malic acid (MA), citric acid (CA), volatile acid (VA), soluble solids (SS), density, and the content of free amino acid as formol number (FN). Some apple juices on the Czech market contain added vitamin C, and the AA content of such juices (268–632 mg L–1) is several times higher than that of apple juices without added vitamin C (around 50 mg L–1). Therefore, the enriched apple juices had a vitamin C content comparable to citrus fruit juices (orange and grapefruit). All contents were compared separately for juices made from concentrate and for directly pressed juices. The effect of the production method was statistically significant (P < 0.05) only for TPC in apple juices, where it was major [473 ± 136 mg gallic acid equivalents (GAE) L–1 from concentrate vs. about twice the value of 798 ± 193 mg GAE L–1 in directly pressed juice], and only to a smaller extent for TA in grapefruit juices (12.5 ± 0.8 g L–1 from concentrate, which was about 30% more than in directly pressed juice).

English. vitamin C; polyphenols; squeezed juices (100%); juices from concentrate (100%); fruits

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