# Usefulness of Rowanberry for Improving the Nutritional Value of Buckwheat Flour Extrudates
## 1 Introduction  
Extrusion cooking is a process that has been known for over 70 years. Processed raw materials undergo a series of transformations due to the influence of high temperature with a certain amount of water available in the raw materials, high pressure when compressing the material, and rapid expansion after leaving the die. During the processing of food and feed, the following mainly occur: gelatinisation of starch, increasing the viscosity of the processed slurry, protein denaturation, fat hydrolysis, formation of fat-protein and fat-starch complexes, inactivation of unwanted enzymes, and microbiological sterilisation of the material. Food manufacturers increasingly use extrusion to reduce production costs and introduce new and attractive foods to the market. In addition, the extrusion is faster than traditional processing methods [1, 2]. Extruded products are especially popular in Asian countries. The quality of the texture of extruded products is significantly influenced by the raw materials and formulation employed in their production. It is also hypothesised that they can have a significant impact on the consumer acceptability and functional properties of these products [1, 3]. Products made from wheat flour have excellent structure-forming properties and retain basic rheological features due to the content and properties of gluten. However, gluten is responsible for many health problems because of intolerance, hypersensitivity, and celiac disease [4, 5]. Therefore, the gluten-free food and beverage markets are rapidly growing. Gluten-free extruded products are of primary interest to food producers [6]. Buckwheat, agluten-free pseudocereal, is one of the prominent raw materials used in the production of extruded products because of its suitability for extrusion [7]. Common buckwheat (_Fagopyrum esculentum_) has been cultivated in Europe for centuries. It is one of the traditional crops cultivated in the world. Poland is fifth in terms of buckwheat production [8]. In recent years, the interest in buckwheat has increased due to the consumers' interest in traditional foods and local products. In particular, buckwheat flour and groats are an essential source of polyphenic compounds with high antioxidant activity, vitamins and minerals, starch, protein, fat, and dietary fibre. They are excellent raw materials for producing extruded products [9]. Buckwheat proteins (albumins, globulins, prolamins, and glutelins) are characterised by high biological value. Unlike cereals, buckwheat proteins are rich in lysine, arginine, and aspartic acid but contain less glutamic acid and proline [10]. They are characterised by relatively low digestibility but can prevent obesity and constipation since they act similarly to dietary fibre. Buckwheat is reportedly capable of lowering cholesterol levels and exhibits hypotensive, antibacterial, and antidiabetic effects [11]. In order to improve the structure of buckwheat products, [PERSON] et al. [12] and many other authors tried to use gelatinised starch as an effective structuring agent due to its light elastic properties. This process can be replaced by using a low-temperature extrusion process (below the degree of expansion) with the addition of other raw materials, e.g., corn grits. Corn is a gluten-free grain often preferred as a source of corn starch in extruded snacks. Although corn is rich in lutein and zeaxanthin, its nutritional composition is insufficient for a healthy diet [13;14]. Although gluten-free products are generally nutritious, they are inadequate in textural, nutritional (such as low protein and fibre, high-fat content), and sensory properties compared to gluten-containing products [15]. This situation has increased the demand for extruded products with high nutritional value and bioactive properties (such as antioxidant activity) [16]. Adding antioxidant-rich ingredients to extruded products enriches the product with bioactive compounds that are beneficial for health.