**1. Introduction**

Ginger cakes are traditional pastries from Central and Eastern Europe. The very important feature of ginger cakes is their ability to remain fresh and savoury for a long time. Currently, ginger cakes are baked on the basis of wheat and rye flour. However, a traditional recipe for ginger cakes was based on the use of rye flour. In Poland, rye (*Secale cereale* L.) is an important grain for bread making and cookies production; therefore, in 2012 18 % of cereal products were made of rye [1]. Rye grain is considered to be a good source of biologically active compounds like antioxidants [2]. Referring to the up-to-date literature, it is highlighted that there is a lack of wider use of buckwheat in pastry.

The buckwheat is a rich source vitamin B1 and B2, lysine, protein with balanced amino acid composition [3], flavonoids [4], phytosterols [5], soluble carbohydrates, D-chiro-inositol and other fagopyritols [6] and thiamin-binding proteins [7]. Buckwheat is also rich in antioxidant compounds such as flavonoids, phenolic acids, tocopherols, reduced glutathione, inositol phosphates and melatonin [8]. Furthermore, buckwheat contains a high amount of rutin (quercetin-3-rutinoside) and has antioxidant, anti-inflammatory and anticarcinogenic properties [9]. According to various chemical compositions, buckwheat-based products were found to display several biological activities, including the increasing number of lactic acid bacteria in rat intestine, treatment of allergic inflammation, reducing the serum glucose level, suppressing cholesterol level, inhibiting protease and scavenging free radicals [10, 11]. These healthy and dietary benefits of buckwheat are main aspects in determining the usage of buckwheat to produce functional products.

The wide spectrum of buckwheat-based bakery and pastry products, e.g. bread, biscuits, crackers, cookies or muffins, was designed by researchers [12]. Mancebo et al. [13] observed that consumers' rating of cookies prepared from buckwheat did not reach high quality score which was mainly related to unpleasant and pungent taste of buckwheat. Therefore, Filipčev et al. [14] noted that 30 % of buckwheat flour is appropriate to create buckwheat-based product with high sensorial acceptability. Chlopicka et al. [15] also showed that 30 % addition of buckwheat flour is highly acceptable, and moreover buckwheat bread has a high antioxidant potential. Moreover, while analysing gluten-free products' sensory profiles, Loredana et al. [16] suggested that the optimum buckwheat flour addition is different for cake, cookies and muffins. The optimum amount in cake was established on the level of 30 % and 10 % for cookies, while for muffins 20 %. Not only the optimisation of the recipes but also technological process parameters for buckwheat-based product preparation have acquired an increasing interest. Lee [17] achieved high overall acceptance for steam bread (wheat with 3 % of buckwheat flour). However, the addition of buckwheat flour was not as high as in the previous studies yet, during the steaming process, not as high amount of an undesirable Maillard reaction products may be formed. Moreover, it is said that dough fermentation step can lead to nutritive and antinutritive compound formation, but some studies also suggested that fermentation process negatively influenced sensory properties of Turkish bread yufka supplemented with 10 % of buckwheat flour [18, 19].

The baking process is inherent in Maillard reaction product formation. The Maillard reaction is a reaction which might have nutritional and toxicological effects on processed food. The Maillard reaction is initiated by the reaction between the carbonyl group of a reduced sugar and a free amino group of proteins, and then subsequent and parallel reactions go. The progress of the reaction can be considered in the context of early, advanced and final Maillard reaction product formation such as furosine (ε-N-2-furoylmethyl-l-lysine) [20], fluorescent intermediary compounds (FIC) formed at the advanced stage [21], carboxymethyllysine (CML) [22] and melanoidins [23]. The latter are responsible for product's colour formation, nevertheless possessing the ability to scavenge free radicals. The degradation of proteins is usually expressed as FAST index [24], based on the measurement of the fluorescence of tryptophan and formation of intermediatory compounds. Moreover, in thermally treated food *via* Maillard reaction, dietary advanced glycation end products (dAGEs) can be formed [25]. dAGEs are an important contributor to the total pool of AGEs formed in the living organism and can induce oxidant stress and inflammation resulting in increasing risk of diabetes and cardiovascular diseases [26]. The AGE accumulation in the body can be regulated by low dAGE diet or by consuming food with natural AGE inhibitors such as plant extracts and plant products, which are good source of antioxidant polyphenols [27, 28]. Thereby, the high antiglycation potential of wheat-buckwheat bread extract has been recently reported [29].

Gathering all the above-mentioned information led to enriching the traditional ginger cakes recipe with 30 % of light buckwheat flour or flour obtained from roasted buckwheat groats. The new recipe for buckwheat ginger cakes has been created, which fits well with contemporary trends in the bakery. Furthermore, characterisation of the changes occurring during fermentation and baking processing and effect of rutin supplementation should be valuable for the understanding of quality and safety of buckwheat ginger cakes. To achieve the aim, the evaluation of the total phenolics; rutin; products of early, advanced and final Maillard reaction stages; and antioxidative capacity of rye-buckwheat ginger cakes enriched with rutin was addressed in this study.
