## 3 Results and Discussion
### Antioxidant Activity  
Various methods were used to examine the antioxidant activity of the obtained powders and to compare it with the activity of the cloudy juice used to produce them. Two of them are used to measure the basic mechanisms of breaking the free radical reactions, i.e., single-electron transfer, SET (reducing capacity measured at pH 7 with the CUPRAC method) and hydrogen atom transfer, HAT (measured at physiological pH using the crocine-bleaching assay, CBA). Methods utilizing ABTS cation radicals and DPPH radicals are based on mixed mechanisms, and the ability to chelate Fe (II) ions determines the supporting effect by removing pro-oxidant Fe (II) ions from the reaction environment. The tests were carried out using extracts in 70% acetone and in phosphate buffer pH 6.5, applied also to determine the content of phenolics and betalains. Most studies do not focus on the antioxidant properties of beetroot powders. However, [PERSON] et al. (2016) analyzed the total antioxidant potential (TAP) in beetroot juice and powder [28]. The authors noted the powder's TAP of 95.31 \(\pm\) 0.68%, which was significantly higher than for raw beetroot juice (80.48 \(\pm\) 0.25%). The authors concluded that this phenomenon resulted from drying, as it concentrated bioactive compounds in the product which resulted in a higher antioxidant activity. Compounds extracted from the cloudy juice with buffer had more than twice the reducing capacity (CUPRAC) of the compounds extracted with 70% acetone. Even greater differences were found when comparing the extracts from dried material (Tables 4 and 5). The highest reducing capacity was detected in the powders obtained by drying concentrated and raw juice at a reduced temperature (J90c and J90: 2907-3311 mg Trolox/100 g in buffer and 518-544 mg/100 g in 70% acetone). The activity detected in both extracts in the powders obtained with carriers (JMD130, JN130 and JK130) and from the juice with beetroot waste (MJ130) was the most suppressed, except for the high reducing capacity of the compounds extracted with the buffer in JM130. After converting the activity into d.m. of the material originated from beetroot, there was a clear decrease in the reducing capacity of the compounds extracted from juice dried with carriers (approximately 300 mg Trolox/100 g d.m.) in relation to the raw juice before drying (1236 mg Trolox/100 g d.m.) and this was slightly lower in juice dried without a carrier at the temperature of 130C (J130: 423 mg Trolox/100 g d.m. ), and especially in juice dried at a reduced temperature (J90: 537-562 mg Trolox/100 g d.m.). A different situation was observed in the case of the extracts in buffer, because the compounds isolated from the material dried without carriers and using powdered milk as a carrier (JM130) had similar or greater activity (2358-3739 mg Trolox/100 g d.m.) than compounds isolated from juice (2782 mg/100 g d.m. ), and slightly lower for other powders with carriers (1391-1978 mg/100 g d.m.). This suggests that phenolic compounds present primarily in acetone extracts were less important in terms of reducing capacity and that the transformations occurring during contact with oxygen at a high temperature (during drying) had a clearly unfavorable effect on this property, unlike water-soluble compounds such as betalains. [PERSON] et al. (2023) [33] determined a similar or greater reducing activity in a CUPRAC assay (2300-9100 mg Trolox/100 g d.m.) after the extraction of conventional beetroots with 50% acidic methanol. The extractant can be to some extent treated as a combination of the two solutions applied in our study, taking into consideration its properties. The most important factor influencing the results was the investigated material--the whole tissue in the aforementioned study vs. cloudy juice in our research. The activity of commercial beetroot products tested by these authors was also similar (325-7800 mg Trolox/100 g).