## 2 Results and Discussion
### Volatile Maillard Reaction Products Formation
[11] observed that pentanal concentration decreased in model cookies after tocopherol addition, however after application of rosmary extract the amount of pentanal significantly increased. Hexanal amount decreased by 12% in biscuits with 30% buckwheat flour addition, then another 1.75-times and 2.40-times in RBB-L and RBB-H, respectively in comparison to RBB (Table 3) (\(p<0.05\)). Our findings are in accordance to [PERSON] and [PERSON] [10], who evaluated that raspberry seeds addition decreased formation of hexanal in cereal flakes. The hexanal concentration in rye-buckwheat biscuits is 10-times higher than that identified in flakes. This might be due to the fact that higher temperature was used in biscuits baking procedure. Hexanal was recognized as a one of compound with the highest concentration and contribution to the buckwheat aroma [7]. Moreover, hexanal is known as important indicator of food samples quality after longer storage period. Negative correlation coefficients between hexanal vs. rutin and TPC contents; and hexanal vs. DPPH and OxHLIA were calculated (r = \(-0.77\); \(-0.81\); \(-0.88\) and \(-0.86\)). Amongst ketones 2-heptanone and 2-nonanone were determined. Ketones are mainly formed in lipid oxidation process. The highest amount of 2-heptanone was determined in RBB-H. Our observations are similar to [PERSON] et al. [11], who reported that a mix oftocopherol and ascorbic acid significantly increased the peak area of 2-heptanone. It can be said that rutin supplementation might positively influence then quality of rye-buckwheat biscuits during storage. **Terpenes** are a varied group of volatile metabolites synthetized generally by plants [30]. A great number of terpen were previously described in spices, which are ingredients in the spice mix used in the biscuit recipe: \(\alpha\)-pinene in nutmeg, anise, coriander, pepper and fennel, \(\beta\)-myrceine in nutmeg and coriander, 1,8-cineole (eucalypt) in cinnamon, D-limonene in anise, pepper and fennel, and carophyllene in cinnamon, clove and pepper [31]. However, \(\alpha\)-pinene and D-limonene were also found in buckwheat aroma profile [7]. Not significant changes were observed in terpen identification, only carophyllene increased 1.50-fold in RBB samples and in samples with rutin addition (\(p>0.05\)). **Pyrazines**. Pyrazines are volatile compounds formed via Maillard reaction and have characteristic nutty and roasty aroma. Increasing rutin addition from 5 mg up to 50 mg per 100 g of biscuits caused an increase in pyrazine content (\(p<0.05\)). The methylpyrazine content increased 1.7-times in comparison to control and RBB. Then, in 2,5- and 2,3-dimethylpyrazine no significant difference after buckwheat flour addition was observed (\(p>0.05\)). Therefore, 2,3-dimethylpyrazine increased by around 16% and 2,5-dimethylpyrazine 2-times in RB-H. 2,6-methyl- and ethylpyrazines, were not present in control and RBB samples. They appeared in RBB-L and their concentrations significantly increased in biscuits with medium and low rutin additions (\(p<0.05\)). These findings are in accordance to [PERSON] [32] and [PERSON] et al. [3], who reported that pyrazine formation can be induced by the addition of ascorbic acid (strong antioxidant). Ascorbic acid can react with amino acids and form final stages of different pyrazine derivatives. Also, [PERSON] and [PERSON] [14] demonstrated that the addition of another antioxidant (epicatechin) influenced the higher amount of methylpyrazine present. **Furans. ** Among furan derivatives, furfural and furfuryl alcohol were identified in rye-buckwheat biscuits (Table 3). It is known that high concentrations of furfural in bakery products may cause allergic skin reactions in consumers and furfuryl alcohol can cause a bitter taste of baking products. Furfural was identified as a main volatile component in buckwheat honey [8]. [PERSON] et al. [33] established that baking bread for 30 min is the appropriate time to avoid significant amount of furfural.