## 2 Results and Discussion  
Total Phenolic Compounds (TPC) and Rutin Contents, and Antioxidant Capacity of Rye-Buckwheat Biscuits  
Flours, buckwheat honey and spices are the main sources of phenolic compounds in rye-buckwheat biscuits. The TPC of control biscuits was 0.90 mg GAE/g DW, while in buckwheat biscuits and biscuits at low, medium, and high ruitin addition (RBB-L, RBB-M, and RBB-H, respectively), the TPC ranged from 2.22 to 22.39 mg GAE/g DW (Table 1). The addition of buckwheat flour was found to have an influence in increasing TPC content 2.5-times (from 0.90 in control to 2.22 mg GAE/g DW in rye-buckwheat biscuits (RBB)). The highest TPC content was measured in RBB-M and RBB-H samples. TPC increased in RBB-M and RBB-H about 12 and 25-times, respectively, in comparison to control biscuits; and 5- and 10-times in comparison to RBB. [PERSON] et al. (2016) reported significantly lower TPC content (0.52 mg GAE/g DW) in wheat-wholegrain buckwheat bread (flour mixed ratio 70:30%, w/w) than in rye-buckwheat biscuits. Moreover, TPC content in RBB sample was slightly higher than in wheat-buckwheat bread (2.65 mg GAE/g DW) ([PERSON] et al., 2016). This may also be due to the fact that in the rye-buckwheat biscuit recipe buckwheat honey and spices highly contribute to the overall amount of TPC. Among phenolic compounds, buckwheat contains high amounts of rutin in comparison to other cereal and pseudo cereal grains ([PERSON] et al., 2016). The concentration of rutin was determined in an 80% (\(\
u\)/\(\
u\)) methanol extract of rye-buckwheat biscuits with the HPLC method. The results are presented in Table 1. This measurement is necessary to check the adequate rutin amount in final product after baking process. It is known that rutin is not heat-stable and that it can degrade in the baking process, probably to quercetin ([PERSON] et al., 2016). [PERSON] et al. (2016) declared that around 40% of rutin degraded during baking in gluten free breads. [PERSON] et al. (2016) established that rutin content in buckwheat flour (_Fagopyrum esculentum_ M.) is about 120 \(\mu\)g/g DW whereas [PERSON] et al. (2016) reported that content of rutin in light buckwheat flour is at the level of 87 \(\mu\)g/g DW. Supplementation of the biscuit formula by different amounts of rutin resulted in a progressive increase in the rutin content in cakes RBB-L, RBB-M and RBB-H. Most significantly, rutin content increased in RBB-M and RBB-H samples, 4-times and 9.6-times, respectively. The functional properties of rye-buckwheat biscuits were evaluated with in-vitro antioxidant assays. The values of antioxidant properties results, expressed as DPPH and FRAP values, are summarized in Table 2. The DPPH values of rye-buckwheat varied from 2.84 (RB) to 3.22 \(\mu\)mol Trolox/g DW (RBB-H), whereas the control biscuit extract scavenged DPPH radicals at a level of 2.65 \(\mu\)mol Trolox/g DW. The buckwheat flour addition at the 30% level in the formulae resulted in significant differences (\(\rho<0.05\)) in the antioxidant capacity. Similar results have been presented in previous studies by [PERSON] et al. (2017), who reported increasing DPPH values according to increasing incorporation of buckwheat flour. Neither low nor medium rutin addition had a significant influence on increasing antioxidant status of rye-buckwheat biscuits. The highest DPPH scavenging ability was observed in RBB-H, in which the high level of rutin addition increased at 22% and 13% in comparison to control and RBB samples, respectively. The scavenging ability of rye-buckwheat biscuits against DPPH radical was not as high as for wheat-buckwheat (70:30, \(w\)/\(w\)) bread ([PERSON] et al., 2016). This might be due to the high temperature used during the rye-buckwheat biscuits baking process, which might enable