# Buckwheat Seeds: Impact of Milling Fractions and Addition Level on Wheat Bread Dough Rheology
## 1 Introduction  
Buckwheat is a pseudocoreal of renewed interest that gained popularity as it often provides a distinguished nutritional and health-promoting value [1, 2]. The genus _Fagopyrum_ includes three species (_F. esculentum_, _F. tatatarium_, and _F. cymosum_), but _F. esculentum_ Moench is widely cultivated for human consumption [3, 4]. Buckwheat seeds flour is considered to be a remarkable resource for functional food development and was used as an ingredient in bread, pasta, cake, and pancake [5, 6, 7, 8] due to its nutritional quality and bioactive compounds. The major nutritional components in buckwheat seeds are represented by the carbohydrates that vary between 63.1 and 82.1%, of which from 54.5% to 54.7% was found to be starch [9] with a relatively high level of amylose (18.3-47% of total starch) [10]. Moreover, buckwheat has high levels of resistant starch (27-33.5%) which provides health benefits [11]. Buckwheat starch is concentrated in the endosperm, similarly to common cereals, while protein and lipids are located in the embryo that extends through the starch endosperm [12]. Buckwheat grains represent an excellent source of dietary fiber (17.8%) with a low ratio of soluble-insoluble dietary fiber (0.5-0.28) [13]. The protein content of buckwheat ranges from 5.7% to 14.2%, depending on the variety and environmental conditions [11]. Buckwheat protein is characterized by a high biological value due to its excellent amino acids balance [14] and it is close to the optimum composition suggested by FAO/WHO [15], making buckwheat an essential contributor to human protein intake. This gluten-free high-quality protein is rich, especially in lysine, methionine, and tryptophan,which are limiting amino acids in most cereals [14; 16]. Lipid content from buckwheat (0.75-7.4%) is higher than that of wheat, being characterized by a high degree of unsaturation, a fact preferable from a nutritional point of view [2; 14]. The main mineral compounds in buckwheat are potassium, magnesium, and phosphorous followed by calcium and other important minerals [2; 17; 18], showing variability among genotypes. Buckwheat grains contain a higher content of vitamins, especially the group of B vitamins, and buckwheat flour was highlighted by the presence of vitamins B2, B3 and B6 [1; 19]. In addition to being a source of nutrients components, buckwheat contains non-nutrient components that present health benefits recognized as bioactive compounds. One group of bioactive components include the phenolic compounds that are of great interest, considering the design and the development of functional food products. Due to the high levels of phenolic compounds, buckwheat can be considered an excellent source of phenols [20; 21]. The supplementation of common cereals like wheat with buckwheat possessing better nutritive value and nutraceutical characteristics would be a feasible strategy to improve the features of final products [22] and dietary diversification. In the literature, most of the study focuses on the levels of buckwheat flours added in wheat flour because the addition in high amounts led to various technological challenges related to the fiber content and due to the gluten dilution effect. As a gluten-free protein, buckwheat has negative effects on dough due to the absence of gluten proteins that form the structure, resulting in poor dough strength. To minimize such an undesirable effect, an appropriate level of buckwheat needs to be used to supplement wheat flour. Nowadays, it is a challenge to produce flour at different particle sizes, because milling fractions varying in physical and chemical properties, and thus offering the possibility to produce flours with specific features for diverse use products [23]. The flour separated on different granularities with high concentrations of valuable components of interest such as proteins, soluble dietary fiber and polyphenols could be used to obtain bakery products with desired features [24]. The functionality of buckwheat milling fractions is essential.