Beetroot is a root vegetable renowned for its high nutritional value. Large portion of commercially produced beetroot is processed into food products, such as pickles or canned boiled vegetable. Commercial importance of this crop lies in the fact that the root is also used for the production of natural red food colorant used in different food products. Industrial processing of beetroot leaves its skin as a waste, not being used for any purpose. Conducted research demonstrated that the skin of the vegetable, considered as a biowaste, contains valuable phytonutrients that were able to be extracted by subcritical water. The content of betalains in subcritical water extract was 6.35±0.31 mg/l, betacyanins 6.60±0.36 mg/l and anthocyanins 10.16±0.90 mg/l. The extracts exhibited high antioxidant (898.88 ± 9.02 mg AAE/l) and antiradical (ABTS: IC50 = 7.19 mg±0.51 dry extract/ml; DPPH = 289.03 ± 3.57 md AAE/l) activities. Beetroot skin is high in dietary fiber cellulose and modified cellulose exhibits prebiotic properties, stimulating growth and activity of beneficial gut bacteria. This prebiotic effect is similar to other well-known prebiotics like inulin and fructo-oligosaccharides. In this research a cellulose fraction from the beetroot skin was hydrolysed by high hydrolytical potential of subcritical water, what was confirmed by quantifying total sugars in obtained extracts (6.6 ± 0.2 mg GE/l). Beetroot skin treatment with subcritical water under adequate operational parameters (130°C, 20 bars N2, 40 min) assured simultaneous extraction of beneficial health-protecting compounds from this biowaste, and obtention of prebiotic fractions. Since pure water was used for beetroot peel treatment it was lyophilized and the dry extract (0.5%) was used in the formulation of sugar-free soft drink for sportsmen (Picture 1). The drink was enriched with 85 mg/l Mg2+, and 1 g/l of L-ascorbate 2-monophosphate, and aromatized with food grade cherry flavor. In preliminary sensory tasting, the beverage was denoted as refreshing, pleasantly flavored, light and overall energizing.

Jaroslava Švarc-Gajić, Tanja Brezo-Borjan, Ana-Marija Vujković Bukvin ; Faculty of Technology, University of Novi Sad, 21 000 Novi Sad, Serbia