*Article* **Buckwheat Seeds: Impact of Milling Fractions and Addition Level on Wheat Bread Dough Rheology**

**Ionica Cot,ovanu \* and Silvia Mironeasa \***

Faculty of Food Engineering, Stefan cel Mare University of Suceava, 13 Universitatii Street, 720229 Suceava, Romania

**\*** Correspondence: ionica.cotovanu@usm.ro (I.C.); silviam@fia.usv.ro (S.M.); Tel.: +40-740-816-370 (I.C.); +40-741-985-648 (S.M.)

**Abstract:** Supplementation of refined wheat flour with buckwheat flour requires a good understanding of the impact of milling fractions, their functionality, and addition level on bread quality. The chemical and functional characteristics of different particle fractions (large, medium, and small) of buckwheat flour on dough Mixolab rheological properties to predict bread quality were investigated. Moisture content, proteins, ash, lipids, and carbohydrates varied irregularly depending on the particle size. The medium particle fraction is the richest in protein, lipid and ash, which are positively correlated with its water and swelling properties and negatively correlated with its volumetric density. The alpha-amylase activity increased with the particle size increase in composite flour. The Mixolab data revealed that the decrease of particle size increased water absorption, dough viscosity during the starch gelatinization and retrogradation stage, while the addition level increased the dough development time and gel stability, and decreased the rate of protein weakening. Following the optimization process and the desirability function approach, it was established that the most appropriate rheological properties are provided by buckwheat flour addition level of 10.75% for medium particle fraction. These results can be helpful for bakery producers to diversify baked products with the desired particle fraction with optimal technological and nutritional properties along with beneficial effects to consumers.

**Keywords:** buckwheat flour; dough rheology; particle size; optimization; wheat flour
