Miroslav ŠLOSÁR, Alžbeta HEGEDŰSOVÁ, İvana MEZEYOVÁ, Mária TIMORACKÁ, Ondrej HEGEDŰS

EVALUATION OF SELECTED QUALITATIVE PARAMETERS OF SWEET POTATO IN DEPENDENCY ON ITS CULTIVAR IN SLOVAKIA

In this study, selected qualitative parameters (total carotenoids, vitamin C, total polyphenols) of sweet potatoes (Ipomoea batatas L.) grown in Slovakia were evaluated. The field experiment was established in the area of the Slovak University of Agriculture in Nitra in 2017. In experiment, registered cultivar 'Beauregard' was used as a comparable cultivar. Other three cultivars ('Dubaian', 'Višnjica white', Višnjica purple') were marked according to the market place from which tubers for seedling production were bought. The sweet potatoes were grown by hillock system and plants were mulched by black non-woven textile. The seedlings were planted on the 1st June 2017. The tuber harvest were realised on the 13th September 2017 and qualitative parameters were analysed immediately after harvest. The carotenoid and polyphenol content was determined spectrophotometrically (polyphenols in lyophilised sample; expressed in mg of gallic acid equivalent.kg-1 of dry weight) and vitamin C content chromatographically (HPLC). The statistically significant differences of parameter content were found among tested sweet potato cultivars. The highest total carotenoid content (TCC) was found in cultivar 'Dubaian' (107.04 mg.kg-1 fresh weight). Generally, significant differences of TCC were detected between cultivars with orange flesh colour (64.87 mg.kg-1 f. w.;107.04 mg.kg-1 f. w.) and cultivars with purple and white flesh colour (3.02 mg.kg-1 f. w.; 8.00 mg.kg-1 f. w.). The highest content of total polyphenols was found in cultivar with purple flesh of tubers - 'Višnjica purple' (5398.77 mg GAE.kg-1 dry weight). Other cultivars were characterized by expressively lower values of total polyphenol content (1557.02-2412.91 mg GAE.kg-1 d. w.). The highest vitamin C content was determined in cultivar 'Dubaian' (436.83 f. w.), following by cultivars 'Beauregard' (309.37 f. w.), 'Višnjica purple' (233.27 f. w.) and 'Višnjica white' (205.73 f. w.). Results of this study showed significant variability of polyphenol and carotenoid content in different-coloured sweet potatoes.

Keywords:

sweet potato, cultivar, carotenoids, polyphenols, vitamin C,

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