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.

"Chimarrao" and "terere" are popular beverages consumed in South America prepared using mate (Ilex paraguariensis St. Hil.). "Chimarrao" consists of a partial infusion where hot water is added, while "terere" is a total infusion, with addition of cold water. This study was designed to simulate preparation of these beverages for consumption, in order to estimate the total amount of xanthines and phenolic compounds in aqueous extracts that would be ingested by the consumer. Different commercial types of mate were employed for "chimarrao" preparation (native, smooth, traditional, and course-ground), and these were compared to "terere". In "chimarrao", beverages from coarse-ground mate showed the highest levels of xanthines. However, "terere" presented quantities 2.5 times higher than the beverage of the coarse-ground mate. Considering the total phenolics in "chimarrao", there was no difference between the types of herbs, but in "terere", the extraction of almost all of the phenolics was observed.

Recebido em 16/7/07; aceito em 11/10/07; publicado na web em 2/4/08 SIMULTANEOUS DETERMINATION OF TARTARIC, MALIC, ASCORBIC AND CITRIC ACIDS IN ACEROLA, AÇAI AND CASHEW PULPS, AND STABILITY EVALUATION IN CASHEW JUICES. The aim of the present study was determining the main organic acids in pulp and juices, as well as evaluating their stability, after opening the package, by liquid chromatography in a C18 column with isocratic elution and UV detection. In açaí pulp tartaric, malic and citric acids were found. Cashew samples presented all of the organic acids evaluated, besides high concentrations of ascorbic and malic acids. Acerola pulp had the highest ascorbic acid concentration. A small decrease in organic acid content during storage was observed. Malic and citric acids seem to be more stable than tartaric and ascorbic acids.Keywords: HPLC; juice; vitamin C. INTRODUÇÃOAs bebidas não alcoólicas têm largo consumo no mundo inteiro. Em todos os países, os levantamentos estatísticos revelam nú-meros crescentes de consumo, tanto per capita quanto global. Esses valores são mais expressivos quando se referem a bebidas obtidas de frutas, pelo fato das mesmas se constituírem em fontes fundamentais de vitaminas e minerais para a dieta humana, além de seus atrativos sabores. 1 A indústria de polpas congeladas de frutas tem se expandido bastante nos últimos anos, notadamente no nordeste brasileiro. As unidades fabris se compõem, em sua maioria, de pequenos produtores que utilizam processos artesanais. A polpa congelada, por apresentar características de praticidade, vem ganhando grande popularidade, não só entre as donas de casa, mas também em restaurantes, hotéis, lanchonetes, hospitais, etc., onde é utilizada, principalmente, na elaboração de sucos. 2As frutas consistem em fonte nutricional de vitaminas, minerais e carboidratos solúveis, sendo que algumas possuem teor mais elevado de um ou de outro nutriente como, por exemplo, a acerola, que apresenta elevada quantidade de vitamina C.3 Esta vitamina é muito importante para a nutrição humana, sendo o ácido L-ascórbico sua principal forma biologicamente ativa. Como um antioxidante potente, tem a capacidade de eliminar diversos radicais livres. 4 Além do ácido ascórbico, outros ácidos orgânicos estão extensamente distribuídos nas frutas e nos vegetais e sua concentração depende de fatores como espécie, solo e circunstâncias de estresse submetidas.5 Os ácidos orgânicos são também largamente utilizados como acidulantes na fabricação de bebidas à base de frutas e vegetais, sendo os principais ácidos utilizados para realçar sabores da bebida os ácidos cítrico e tartárico. Além disso, o ácido cítrico é muito utilizado como acidulante em sucos de fruta, porque o pH dado por ácidos naturais não é suficiente para assegurar a estabilidade microbiana a longo prazo. 6O ácido ascórbico é amplamente utilizado como antioxidante em sucos, entretanto, por causa de sua natureza, é oxidado durante o período de estocagem. A literatura apresenta vários relatos sobre a estabilidade do ácido ascó...

In this work, the influence of the method of processing on phenolic composition and the in vitro antioxidant activity (AOX) of grape juices was studied. The classic methods of producing “Hot Press” (HP), “Hot Break” (HB), and “Cold Press” (CP), and an artisanal method using steam were compared. Among the methods of elaboration of evaluated grape juices, those that heated the grape showed higher content of bioactive phenolics and AOX. The artisanal method using steam presented acceptable bioactive content and could be simple alternative for grape juice production. The main bioactive compounds quantified in the studied juices were procyanidin B1, quercetin‐3‐pyranoside, chlorogenic acid, malvidin‐3‐glucoside, cyanidin‐3‐glucoside, and petunidin‐3‐glucoside. These were correlated by principal component analysis (PCA) with the antioxidant activity. The characteristics obtained from the different juice elaboration methods demonstrate that the HB method was responsible for the greatest extraction of bioactive compounds from the grapes. Practical applications Worldwide consumption of grape juice has been increasing. The factors that have contributed to this growth include the good sensory acceptance and the nutritional appeal related to bioactive compounds. The bioactive compounds of grape juice are mainly flavonoids and phenolic acids, and several factors exert influence on the phenolic composition of this beverage, among them, the method of elaboration. The present work presents new information on the influence of grape juice processing methods on the profile of bioactive compounds of nutritional interest and contributes to improvements in the production processes of this beverage.

Mate herb, Ilex paraguariensis St. Hil., is a plant cultivated in South America. Studies have evidenced the presence of phenolic compounds in mate herb, however, there are no reports on the contents of these compounds in different types of mate herb sold in the South Region of Brazil. In this study, capillary zone electrophoresis was used to quantify phenolic compounds in three lots of each of four types of commercial mate herb (traditional, native, large ground, and suave). Analysis was performed before and after acid hydrolysis. Hydrolysis time, temperature and chloridric acid concentration were optimized by central composite design to maximize the amounts of free phenolic compounds obtained after hydrolysis. Before hydrolysis, high amounts of rutin were detected, while after hydrolysis, high amounts of caffeic acid and 3,4-dihydroxybenzoic acid were obtained, giving evidence that mate herb should be further investigated as a major source of these compounds.