## 1 Introduction  
Bread, a widely consumed grain product worldwide, is predominantly made from wheat flour [1, 2] which primarily contains starch (60-85%) and proteins (9-12%) [3, 4]. The content of nutrients varies depending on the extraction rate [4]. The production of wheat bread typically involves the use of refined flours, also known as low-extraction flours, which are characterized by low levels of dietary fiber, proteins, mineral components, and bioactive compounds [2, 3]. Furthermore, the proteins present in wheat flour are incomplete, lacking certain essential amino acids (mainly lysine, which limits their digestibility) [3, 5, 6].  
Enhancing the nutritional quality of wheat bread can be achieved by incorporating natural plant-based ingredients into the recipe. Research has validated the positive nutritional impacts of adding herbs and spices to the bread [7, 8, 9, 10, 2, 2, 7], pomace [11, 12, 13, 14, 15], and pseudocrereal flours [16, 17]. Valuable recipe additions can also include flours made from legume seeds [4, 18, 19, 20, 21].  
Leguminous plants belong to the family _Leguminosae_ (or _Fabucae_), which encompasses over 18,000 different species. Their cultivation accounts for approximately 15% of the world's agricultural land [22]. In 2021, the production of legume seeds reached 88.97 million tons [23]. Legume seeds are a valuable source of food for people worldwide [24; 25; 26; 27; 28; 29]. They are a good source of protein, dietary fiber, minerals, vitamins, and bioactive phenolic compounds [30; 31; 32; 33; 34]. Legume seeds contain anywhere from 17% to even 50% protein [35; 34; 36] that has a significantly higher biological value compared to grain protein [26; 32; 34]. They also have a lower glycemic index compared to grains [30; 33; 37; 38]. Consuming legume seeds is recommended for the prevention of type 2 diabetes and can help better control glycemia in individuals with diabetes [39]. Regular consumption of legume seeds can also contribute to the prevention of other chronic diseases, such as obesity, cardiovascular diseases, and certain cancers [30; 33; 40]. Some of the most popular and commonly consumed legume seeds include peas, beans, broad beans, chickpeas, and lentils. Others, such as cowpeas, lupines, vetches, lentil vetches, or white lupines, are still underappreciated [27; 29].  
Grass pea, which has been grown since ancient times, is used in human nutrition and as animal feed is likely the oldest plant in Europe [41]. Currently, interest in this plant is limited to a few species, including _Lathyrus sativus_[42; 43] and _Lathyrus maritiums_[44; 45; 46], mainly cultivated in India, Bangladesh, Pakistan, Nepal, Ethiopia, and China [47]. Grass pea contains 20-36% high-quality protein [48]. Its positive effects in treating cardiovascular diseases, hypoxia, and hypertension have been demonstrated [47; 49; 50; 51].  
Lupine has been cultivated for over 2000 years in Europe and South America [52; 53]. Three main species of lupine are primarily grown: narrow-leafed lupine (_Lupinus angustifolius_), yellow lupine (_Lupinus luteus_), and white lupine (_Lupinus albus_). Lupine seeds have the highest protein content among all legume species (29-52% dry weight) [54]. The main protein groups in lupine are albumins and globulins, which are characterized by their high biological value due to a significant amount of essential amino acids, particularly lysine [1; 54]. Lupine seeds are also a valuable source of carotenoids, tocopherols, and lecithin [4; 55]. Consuming lupine seeds is recommended for the prevention of conditions such as hypercholesterolemia, diabetes, and arterial hypertension [4; 19; 56].  
Due to their high nutritional value and sensory qualities, both grass pea and lupine seeds can be used as ingredients in functional food products [20; 55; 57; 58]. This study aimed to assess the suitability of grass pea and lupine seed flour as a component in sourdough bread recipes using organic wheat flour as a base.