Beetroot peel as a sustainable resource of antioxidants for the food industry

Abstract

Red beetroot (Beta vulgaris L.) is regarded one of the most relevant vegetable due to their valuable nutritional characteristics. However, the industrial processing of beetroot makes high contents of waste such as peel, which could be important source of antioxidant compounds. Therefore, the aim of this study was to establish and compare the amounts of some antioxidants and colour parameters of peel in tested beetroot. The following red beetroot varieties and hybrids were chosen for the research: 'Kosak', 'Alto F1', 'Pablo F1' and 'Taunus F1'. Beetroots were grown in 2021 at a farm in the Širvintų district under traditional conditions. Freeze-dried beetroot peel was used for chemical analyses. Beetroot peel was analysed for total phenolics using Folin–Ciocalteu spectrophotometric method. The total anthocyanins amount of beetroot peel samples were established by the pH differential method. Individual betalains (betacyanins and betaxanthins) were measured by spectrophotometric method. The colour of raw beetroot peel was determined with a spectrophotometer ColorFlex using the CIE Lab system. This study showed that total phenolics amount in investigated beetroot peel ranged from 24.87 to 36.12 mg g-1 in dry matter. The highest amount of this component was found in peels of 'Kosak' and 'Pablo F1'. Significantly the highest amounts of total anthocyanins and total betalains were observed in peel of 'Kosak'. The predominant betalain in beetroot peel was betacyanins. The highest amounts of betacyanins and betaxanthins were quantified in the peel of 'Kosak'. The highest L* values were found for peels of 'Alto F1', 'Kosak' and 'Traunus F1', without differences between them. The values of a* in investigated beetroot peel samples significantly no differed. The lowest b* values were found for 'Alto F1' peel. Summarizing the results of this study it can be concluded that red beetroot peels (especially 'Kosak') are sustainable resource of natural antioxidants. Therefore, special attention should be paid to peel potential uses as an additive for the development of new functional products or to improve the quality of food products.