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a b s t r a c tA liquid chromatographic method for fast and simultaneous determination of tartaric, malic, ascorbic and citric acids was validated for further application to fruits and juices. Moreover, the organic acids content of commercial samples of fruits and juices were evaluated, as well as the ascorbic acid stability during the storage. Determination of organic acids was carried out using a liquid chromatograph coupled to a diode array detector, with reversed phase (C 18 column) and isocratic elution with 0.01 mol L À1 KH 2 PO 4 (pH = 2.60) mobile phase. The validation parameters showed efficiency, adequate linearity, relative standard deviation values between 0.4% and 2.3% (n = 10) for repeatability and from 1.2% to 5.0% (n = 18) for reproducibility, limits of detection (LD) were between 0.03 and 3.31 lg mL À1 and quantification (LQ) were between 0.10 and 11.03 lg mL À1 , recovery rates were between 82% and 110%, for two levels. In addition, the method is fast (10 min) and generates low and non-toxic residues. The values found for vitamin C were about 10 times above the values declared at the package. Ready to drink juices have a composition similar to the fruit, concerning to organic acids, except for the powder juice, in which only ascorbic and citric acids were found, for all tastes. After opening the package, a decrease of 14.0% and 27.0% in ascorbic acid content was observed for orange powder and ready to drink juices, respectively.

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Brazil has a wide variety of tropical, subtropical, and temperate fruits with widely differing carotenoid compositions, providing a good setting for investigating the natural occurrence of cis-isomers of provitamins. Seventy-five samples were analyzed. The fruits could be classified into two main groups:(1) those having @-carotene as the principal provitamin and (2) those with @-cryptoxanthin as the major provitamin. Some fruits also had a-carotene, y-carotene, a-cryptoxanthin, and @-apo-10'-carotenal, usually at low levels. cis-Isomers were not found in caj6, papaya (two cultivars), passion fruit, pitanga, and West Indian cherry. Traces of 134s-@-carotene were found in some samples of loquat, mango (two cultivars), and piqui. Buriti, mamey, nectarine, and peach had 0.1-4.2 pg/g 13-cis-fl-carotene and 0.1-1.0 pg/g 9-cis-@-carotene; the latter two fruits and piqui also had 0.2-0.4 pg/g neo-@-cryptoxanthin. Overestimations of only 3-10 5% of the retinol equivalents occurred when the isomers were not separated, indicating that this separation is not important in fresh fruits.