1. What is isocitric acid, and which foods contain it?
- Isocitric acid is a natural organic acid in the citric acid cycle (TCA/Krebs), metabolized from citrate during metabolism. It is a natural component of all plants and animals, but it usually only appears at very low levels in food.
👉 Foods and products that may contain isocitric acid (or the D-isocitric form):
- Fruit juices and pure fruit juices, especially orange juice and vegetable juices — isocitric acid occurs naturally through the fruit's metabolism and is used as a marker to test the authenticity of fruit juice
- Food products made from fruit/vegetables (for example: beverages labeled "contains orange juice"). The citric acid/isocitric acid ratio can reflect the product's quality and authenticity.
📌 Note: The level of isocitric acid in food is usually very low, so measurement requires a sensitive and accurate analytical method.
2. Testing isocitric acid with the R-Biopharm test kit
- One of the most popular kits is Enzytec™ Liquid D-Isocitric acid (code E8550) from R-Biopharm (Germany), used to determine isocitric acid in food by the enzymatic method.
* Key information about the kit
- Uses an enzymatic method that drives a specific reaction, measured by UV spectrophotometry at a wavelength of ~340 nm.
- Suitable for directly analyzing food samples such as fruit juices, vegetable juices, and products containing these ingredients.
- Includes ready-to-use reagents (R1, R2) and a standard control sample.
📋 Principle of the method
- Sample preparation: extract the food sample to make the test solution.
- Enzymatic reaction: in the test tube, the enzyme in the kit catalyzes a specific reaction with the D-isocitric acid in the sample.
- Signal detection: the spectrophotometer measures absorbance at 340 nm caused by the change of NADPH in the enzymatic reaction — this signal is proportional to the concentration of isocitric acid in the sample.
- Calculating the result: standard samples and a calibration curve are used to compute the concentration of D-isocitric acid in the food sample.
* Advantages of the enzymatic method with the R-Biopharm kit
- Fast, accurate analysis that is easy to repeat — suitable for both manual analysis and automated analyzers.
- Can be used in food quality control laboratories, fruit juice factories, or food analysis laboratories.
3. Applications in food testing
Determining isocitric acid not only reveals the natural amount present, it also detects quality fraud (for instance artificial citric acid added beyond natural levels). National standards also provide an equivalent enzymatic method for determining D-isocitric acid in vegetable juices.
4. Summary
