Samples of orange juices were evaluated according to standard criteria in Code of Practice and compared with standard RSK values (Richtwerte und Schwankungsbreiten bestimmter Kennzahlen). In 15 orange juices, the content of chlorides, total acidity, volatile acids and ammonia did not exceed values in Code of Practice. It was found that samples F and K (66.30 g/dm3 and 57.65 g/dm3) contained more glucose than is allowed by Code of Practice. Juices G and K did not exceed RSK values for the D-isocitric acid content (103.68 g/dm3 and 109.96 g/dm3). Criterion according to citric and D-isocitric acid ratio corresponded to the normal values in 100% orange juice in samples G, K, L and also in 12% orange nectar P (69.3; 118.6; 51.4 and 72.3).
orange juices, adulteration, authentication, isotachophoresis