The qualitative and quantitative constituents of antioxidant properties of fruit, and vegetable, juices were studied by volt‐ampere method. The actual redox power of redox systems connected with normal redox potential (qualitative constituents of antioxidant activity) of juices was increased in the line: carrot, pomegranate, cabbage. Reduction current density for carrot juice redox system was proportional to the square root of hydrogen ion concentration, whereas antioxidant properties of cabbage juices were not affected by pH. Redox reactions between phenolic compounds of mixed juices were forecast based on polarization curves of components on Pt. The antioxidant effect of phenolic compounds of cabbage juice' redox system on anthocyans of pomegranate juice influenced the increasing intensity of absorption in 490–510 nm wavelength region in mixed juice compared with the theoretical value calculated as arithmetic means. Thus, polarization curves on Pt electrode can be recommended as criteria for the evaluation of antioxidant properties of juices. Practical applications Polarization curves on Pt can be useful for forecasting the direction of redox reaction in mixed juices. This is vital for color stabilization of products containing anthocyans, and browning decreasing in colorless products. Results obtained in respect of actual reducing power will assist in improving evaluation of antioxidant properties of fruit, and vegetable, products. Results obtained for carrot, cabbage, and pomegranate, juices can be utilized in the area of canned fruit, and vegetable, products.

Gas chromatography–mass spectrometry (GC–MS) study results, and dilution method results were compared in respect of food flavors in orange juices, which are sold in Ukrainian markets as “natural.” It was shown that the presence of d‐limonene, and benzoic acid, in commercial/industrial orange juices indicates the presence of added food flavors. New scientific evidence demonstrates the correlation between intensity of odor, represented numerically by dilution index (p < 0.05), and GC–MS results. It was established that the comparative evaluation of dilution indexes of industrial orange juices, and freshly squeezed ones, eliminates subjectivity factor, and can be useful for rapid investigation of orange juice authenticity in respect of the presence of food flavors. For orange juices produced with, and without added food flavors, the intensity of odor was found to be 2 times higher, and 1.5–2.5 times lower, respectively, than that of freshly squeezed juice. Practical applications The rapid evaluation of orange juices and concentrates, regarding authenticity, with respect to the presence of food flavors, can be provided by dilution method. The results confirm the potential of odor index as a numerical criterion for characterization of the aroma intensity level in fruit juices and could be of practical relevance. The article is important for food producers, food inspection authorities, and scientists who are working in the area of restored fruit juices.

A new conductometric method for the determination of diluted apple juices has been substantiated. It has been established that the volt-ampere method is useful for the investigation of undeclared ascorbic acid. © 2018 Society of Chemical Industry.