## 2 Results and Discussion
### Sensory Evaluation  
The influence of buckwheat flour and varying doses of rutin addition is presented in Figure 1. After addition of buckwheat flour, the overall quality of RBB (5.8) decreased in comparison to control ones (6.4). These findings are in agreement with [PERSON] et al. [24], who reported that the incorporation of buckwheat flour decreased consumer acceptance of buckwheat based-product. The overall quality score of rye-buckwheat biscuits was established at 5.7, 5.9 and 6.2 for RBB-L, RBB-M and RBB-H, respectively. A score at a level of 6.2 was also achieved for the buckwheat biscuits of [PERSON] et al. [24] with 30% buckwheat incorporation. Moreover, the positive acceptance of buckwheat product was proven by [PERSON] et al. [17]. It can be said that rutin addition didn't significantly influence the acceptance score of rye-buckwheat biscuits. In detail, the 13 sensory descriptors were evaluated by panelists assessing: color, aroma, taste and texture of rye-buckwheat biscuits. The statistically significant difference was observed in color acceptance (\(p<0.0001\)). Therefore, the acceptability of color was lowest for control while the best score was achieved for RBB-L. The 30% incorporation of buckwheat flour significantly increased the color acceptance from 5.13 to 6.03 (\(p<0.0001\)). A similar observation about color of buckwheat-based bread was presented by [PERSON] et al. [25], who reported that buckwheat improved breads' color due to high phenolic content inhibiting the browning compounds' formation via Maillard reaction during baking. Moreover, the color of rye-buckwheat biscuits is more attractive than for rice-buckwheat cookies with the same amount of buckwheat flour [19].  
In case of odor and taste, only for aftertaste significant difference was noticed between control and rye-buckwheat biscuits (\(p<0.001\)). The 30% buckwheat flour incorporation influenced, while rutin addition didn't affect the aftertaste impression. The pungent and bitter taste of rye-buckwheat biscuits can be related to high concentration of rutin and catechin in buckwheat flour [26]. Bitter taste increased significantly (\(p<0.0001\)) in rye-buckwheat biscuits with medium and high rutin addition, RBB-M and RBB-H, respectively. To avoid problem with strong bitter taste of buckwheat, some researchers are working on non-bitter type of buckwheat, which might in future increase consumption of buckwheat [27]. The high contribution to panelists acceptation might have been associated with sweet and spicy taste. For sweet taste, the addition of buckwheat honey and sugar are responsible, whereas spicy taste is related to spice mix incorporation to biscuits recipe. Attractiveness of buckwheat biscuits is probably also elaborated by cinnamon taste and odor, which are linked to cinnamon presented in spice mix.  
Regarding textural properties, incorporation of buckwheat flour negatively influenced the hardness of biscuits in comparison to control, however the difference was not statistically significant. The rye-buckwheat biscuits were harder to bite than rice-buckwheat cookies as was studied previously by [PERSON] et al. [19]. The worse score for hardness in our experiment might be due to different rheological properties for rye dough. However, in latest studies by [PERSON] et al. [19], panelists declared also a high score for crispness of rye-buckwheat biscuits. The graininess of rye-buckwheat biscuits, which describes unpleasant mouth feeling, could be attributed to the coarse granularity of buckwheat flour. [PERSON] et al. [28] noted very good textural properties of cookies with green tea addition, however in our case usage of gluten-free buckwheat flour is a main problem to achieve high rheological scores.