The effects of boiling and fermentation on betalain profiles and antioxidant capacities of red beetroot products

•Red beetroot products contained twenty two different betalains.•Applied techniques reduced the content of betalains by 51–88%.•Red beetroot peel protects betalains from degradation during heat treatment.•Microbial activity and matrix softening caused betalains release under fermentation.•Red beetroots products possess own betalains fingerprint and antioxidant capacity. The aim of study was investigation the impact of boiling and spontaneous fermentation on profile and content of betalains and antioxidant capacity of red beetroot. Betalains were analyzed by micro-HPLC-TOF-MS/MS method, while antioxidant capacity by three in vitro assays. Red beet products were abounded in betalains, with betanin, isobetanin, betanidin and vulgaxanthin I predominating among twenty two pigments identified. Boiling and fermentation of red beet reduced the content of betalains by 51–61% and 61–88%, respectively, however, this decline was limited when the peel was present. Microbial activity and softening of the matrix induced by the fermentation process led to the release of betalains responsible for strong antioxidant capacity of the juice formed. Generally, the treatment applied maintained and/or lowered antioxidant capacity of red beet materials obtained. Our findings indicate that red beet-derived products are valuable source of betalains, with their profile, content and antioxidant capacity being modulated by processes applied.