Determination of Citric Acid in Fruit Juices
Citric acid is an organic acid naturally present in fruit and, consequently, also in juices. However, it can be added as an additive to regulate the acidity of the product. Its presence lowers the pH, creating an unfavorable environment for the growth of pathogenic microorganisms and thus helping to extend the shelf-life of the juice. An excessively low content can compromise conservation, while excessive levels can alter the flavor.
Method
Sample treatment
The sample must be centrifuged (code 222061) before the analysis.
Principle of the test
Through an enzymatic reaction, citric acid is converted to oxaloacetate and then to malate which reacts with NADH to produce NAD+. The decrease in absorbance, measured at 366 nm (end-point), of the NADH solution is proportional to the amount of citric acid present in the sample.
Calibration curve
The calibration curve of the CDR DrinkLab system, carried out using HPLC as a reference method, confirmed excellent linearity of the system throughout the measurement range.
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Measuring range
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