Background: The interest in potato juice as a therapeutic agent goes back to the 19th century but its application was not supported by any knowledge about biological activity of this raw material. Factors restricting the medical application of potato juice include its inattractive sensory and functional properties. The aim of the presented investigations was preliminary evaluation of the biological activity of potato juice and the impact on it of some technological operations such as: cryoconcentration and hydrolysis in a membrane reactor.
Material and methods: Experiments comprised investigations of antioxidative potentials of fresh potato juice, products of its processing as well as fractions separated because of the size of their molecules using, for this purpose, Folin-Ciocalteu methods and reactions with the ABTS cation radical.
Results: The value of the antioxidative potential of fresh potato juice determined by means of the ABTS reagent corresponded to approximately 330 μmol/100 g which is in keeping with literature data. As a result of the cryoconcentration process, the value determined by the Folin-Ciocalteu method was found to increase only slightly whereas the value determined by means of the ABTS reagent almost tripled. The antioxidative potential was found to grow even more strongly in the case of the application of both methods when the process of enzymatic hydrolysis was employed. The total of 5 protein fractions of molecular masses ranging from 11 000 Da to over 600 000 Da, as well as an organic non-protein fraction of the molecular mass of 600 Da, were obtained as a result of the performed separation. All the examined fractions exhibited antioxidative activities. The highest values determined by the Folin-Ciocalteu method were recorded for the protein fraction of 80 000 Da mean molecular mass, while using the ABTS reagent--for the organic, non-protein fraction.
Conclusions: Potato juice possesses antioxidative activity which can be enhanced by means of processing, especially, in the course of enzymatic hydrolysis. In addition, it was demonstrated that the organic nonprotein fraction of 600 Da mean molecular mass was characterised by the highest antioxidative activity.