Organic Acids In Fruit Juices Research Articles

One-step pre-column derivatization method for HPLC-UV determination of organic acids in fruit juices

A simple and effective one-step pre-column derivatization method for reversed-phase HPLC-UV determination of the major organic acids (citric, malic, tartaric, and succinic acids) in fruit juices has been developed. The method is based on the coupling reaction of organic acids with 1-naphthylamine in the presence of N,N′-diisopropylcarbodiimide. The resulting organic acid amide derivatives were successfully separated on an AQ-C18 column and detected by a UV detector at 222 nm. Isocratic elution was performed using an acetonitrile-methanol-tetrahydrofuran-water (37:4:1:58; v/v) mixture as a mobile phase at a flow rate of 2.0 mL/min. Validation studies showed good recoveries ranging from 88.97 to 92.52% with RSD % between 2.95 and 4.56%. The detection limits obtained were 0.18, 0.48, 0.14, and 0.69 µg/mL for tartaric acid, malic acid, succinic acid, and citric acid, respectively. The method was successfully applied to three different commercial fruit juice and nectar samples with little or no clean-up procedures.

Gas chromatography-mass spectrometric determination of organic acids in fruit juices by multiwalled carbon nanotube-based ion-pair dispersive solid-phase extraction and in situ butylation.

Fruit juices are naturally acidic, and the acidity is due to the formation of various organic acids formed in several metabolic processes. The content of acids varies due to various processing parameters during the preparation of fruit juices and their packaging for commercialization. Quantitative determination of organic acids provides the necessary information leading to changes occurred during processing. The organic acids were extracted by ion-pair dispersive solid-phase extraction by multiwalled carbon nanotubes and analyzed using gas chromatography-mass spectrometry (GC-MS) and in situ butylation. The developed analytical method was validated, and the obtained results showed a linearity in the range of 0.5-5000 μg/L levels of the analytes with limit of detection and quantification values of 2-10 and 5-20 μg/L, respectively. The inter- and intra-day reproducibilities are less than 15% with 80%-98% recoveries and less than 20% matrix effect. The developed method was used for the quantitative determination of organic acids present in fresh and packaged apple, grape, orange, and pomegranate juice samples. The content of organic acids was observed in the range of 0.26-3793 μg/L. Pimelic acid was not detected in any of the analyzed fruit juices. Fumaric acid (FA) was observed to be a major organic diacid present in the natural fruit juices. The results indicated that the processing of fruit juices for packaging decreases the content of organic acids in fruits. The developed GC-MS-based analytical method for the analysis of organic acids has good sensitivity and reproducibility for the quantitative determination of various organic acids in fruit juices. FA was observed to be the major carboxylic acid present in fruits. The processed juice samples possess the lowest concentration of organic acids, suggesting that processing has a significant effect on the concentration of organic acids in fruits.

Simultaneous voltammetric determination of four organic acids in fruit juices using multiway calibration

A sensitive, fast, and inexpensive square wave voltammetric method using a cobalt phthalocyanine modified carbon paste electrode was developed for simultaneous determination of citric, lactic, malic and tartaric acids in fruit juices. To overcome the strong overlap of voltammetric signals caused by calibrated and uncalibrated constituents, multivariate curve resolution with alternating least squares (MCR-ALS) was used. Data were previous treated for correction of baseline and potential shift. The MCR-ALS calibration models were constructed and evaluated using a validation set obtained from a Taguchi design. The values predicted by the optimized MCR-ALS models were unbiased and no statistically significant difference was observed between proposed and reference methods, applying the paired t-test at a confidence level of 95%. As far as the authors know, a voltammetric method that simultaneously determines four organic acids in complex samples such as fruit juices without any previous pretreatment has not yet been reported in the literature.

Determination of Organic Acids in Fruit juices by UPLC

A reversed phase UPLC method for separation and quantification of organic acids (oxalic, citric, tartaric, malic and ascorbic and lactic acids) in fruit juices was developed. The chromatographic separation was performed with a Surveyor Thermo Electron system at 10°C by using a potassium dihydrogen orthophosphate buffer (pH3.1) as mobile phase, an Hypersil Gold a Q Analytical Column and diode array detection at λ=254 nm for ascorbic acid and λ=214 nm for the other organic acids. Organic acid profiles of seven species of fruits: sweet orange, white and red apple, lemon, lime, white and pink grape fruit were established. Species significantly affect the organic acid distribution of fruit juices. In all juices, the most abundant organic acid was citric acid, ranging from 5.22 to 62.42g/l. Fruit juices are good sources of ascorbic acid (0.137-0.625g/l). The average ascorbic acid was the highest in lemon juice followed by sweet orange juice, sweetie and white grapefruit.DOI: http://dx.doi.org/10.3126/ijls.v9i5.12690

Analysis of Organic Acids in Fruit Juices by Liquid Chromatography−Mass Spectrometry: An Enhanced Tool for Authenticity Testing

Organic acid analysis plays a fundamental role in the testing of authenticity of fruit juices. Analytical methods used routinely for organic acids suffer from poor reproducibility, often give false positives/negatives for tartaric acid, and do not offer the possibility of analyte confirmation. There are conflicting reports in the literature on the presence/absence of tartaric acid in pomegranate juice, a potential indicator of adulteration with grape juice. In this work, a method based on stable isotope dilution liquid chromatography-tandem mass spectrometry is described for citric, malic, quinic, and tartaric acid in fruit juices. Validation data including precision and recovery in six types of juice are presented. Tartaric and quinic acids were confirmed in pomegranate juice at concentrations of 1-5 and ∼1 mg/L, respectively. These concentrations are much lower than those resulting from adulteration with grape juice and apple juice, respectively, at the 5% level. A separate method for isocitric acid in orange juice based on the single standard addition method is also described.

A quick method for the simultaneous determination of ascorbic acid and sorbic acid in fruit juices by capillary zone electrophoresis

A method of quickly determining ascorbic acid and sorbic acid by capillary zone electrophoresis with ultraviolet detection was developed. The choice of background electrolyte, wavelength, injection time and applied voltage were discussed. Ascorbic acid and sorbic acid were well separated in 80 mmol L −1 boric acid–5 mmol L −1borax (pH = 8.0) in 5 min at the detecting wavelength of 270 nm. Under the optimum condition, the method has linear ranges of 2.54–352.00 mg L −1 for ascorbic acid and 1.08–336.39 mg L −1 for sorbic acid with the detection limit of 1.70 mg L −1 for ascorbic acid and 0.54 mg L −1 for sorbic acid, respectively. Other organic acids in fruit juices have no effect on the detection. This method is very feasible and simple and can be used to detect ascorbic acid and sorbic acid in fruit juices.

HPLC/UV determination of organic acids in fruit juices and nectars

A reversed phase HPLC method for separation and determination of organic acids in fruit juices and nectars is presented. The method is based on the reaction of free organic acids with O-(4 nitrobenzyl)-N,N′-diisopropylisourea (PNBDI) in presence of dioxane. Excess of reagent was removed with a strong cation-exchange resin. The p-nitrobenzyl esters were separated on a C18 reversed phase column using gradient elution with water and acetonitrile and UV detection at 265 nm. Benzylmalonic acid was used as internal standard. The determinations were performed in the linear range of 0.05–2 g/l for lactic, acetic and succinic acids, 0.1–12 g/l for tartaric, malic and citric acids. The detection limits were 0.025 g/l, 0.017 g/l, 0.050 g/l, 0.039 g/l, 0.025 g/l and 0.060 g/l, respectively for lactic, acetic, tartaric, malic, succinic and citric acids. Validation of the method was carried out by the standard additions method, the recoveries ranged from 91.4 to 103.0%. The precision of the method was also evaluated and reported a CV% as less than 3.1%. Organic acid profiles of citrus fruit, pineapple and apple natural juices (home-made), commercial juices and nectars were established.

Use of ion chromatography for the measurement of organic acids in fruit juices

A gradient ion chromatographic method to separate and determine main organic acids in fruit juices was developed. The method allows the separation of organic anions on Dionex OMNI PAC PAX-500 column by NaOH gradient elution and conductometric detection. The main organic acids of fruit juices (citric, malic, tartaric) were separated together with other less abundant acids. More than 500 samples of fruit juices were analysed, mainly orange juices from Brasil, Italy, Florida, California, as well as apple, cherry, grape and blackcurrant juices of different origin. The method has shown a high sensitivity and a satisfactory accuracy. The method also allows the simultaneous separation of lactic and acetic acids, produced by microbiological spoilage of juices, and of some important inorganic anions such as chlorides and nitrates.

Determination of Sugars and Organic Acids in Fruit Juices by FT Mid-IR Investigation of Dry Extract

In an extension of the approach adopted by Meurens et al. for dispersive NIR spectroscopy, the principle of using dry extracts has been applied to FT-IR spectroscopy, to make use of three advantages: the rapidity of Fourier transform spectroscopy, the solvent elimination, and the better peak resolution in the mid-IR region. However, sampling appears more difficult in mid-IR than in NIR spectroscopy. The feasibility of quantitative analysis has, in a first step, been tested on synthetic samples before application to natural fruit juices. The performance of our dry extract method is reported in terms of spectroscopy as well as of multicomponent quantitative analysis of sugars and organic acids in fruit juices.

HPLC FINGERPRINT OF ORGANIC ACIDS IN FRUIT JUICES

Organic acids give fruit products their characteristic tartness and vary in combination and in concentrations among different juices. The organic acid profile can be used to identify a juice or verify its purity. 
 Typically, organic acids in fruit juices are identified and quantified by using methods such as HPLC. In this procedure, reversed phase column is used to separate and identificate six organic acids. Because several of the analytes are extremely difficult to resolve, a aqueous mobile phase is needed to enhance interaction between the acids and the C18 stationary phase.

Paper Chromatographic Detection of Major Organic Acids in Fruit Juices

Abstract The official AOAC paper chromatographic method for organic acids in vanilla extract has been modified slightly for fruit juices. Fruit juices are characterized by simple major organic acid patterns, so that addition of a foreign acid or cheaper fruit juices can frequently be detected by significant changes in the major organic acid pattern. A standard acid solution, developed simultaneously, provides a rough measure of the acid spot intensities. Eight collaborators participated in the examination of the two samples submitted. Two authentic juices were also provided for comparison purposes. All collaborators correctly found the unknown cherry juice to be adulterated with citric acid. Seven of the eight collaborators also reported correctly that the unknown blackberry juice was adulterated, although the acid pattern of this juice is more complicated and the addition of citric acid is more difficult to detect. The method is recommended for adoption as official first action.