## 1 Introduction  
Sustainable food production and consumption are becoming a priority for the food industry, which is faced with the challenge of reducing the negative impact of its activitieson the environment. In this context, the use of the by-products generated during food processing is becoming increasingly important. By-products, such as pomace, can be valuable secondary resources that, after appropriate treatment, can be reused, thus contributing to waste reduction and supporting a more sustainable economy. Such an approach not only minimizes waste but also promotes the creation of a circular economy model, in which waste is transformed into valuable raw materials, while supporting the development of a sustainable food industry [1; 2; 3]. The development of the food industry is related not only to the implementation of new techniques and technologies and the development and production of innovative products, but also to the emergence of increasingly new and more effective ways of managing various types of post-production residues. The largest amounts of by-products are generated in the sugar, brewing, and distilling industries, but also during the processing of fruits and vegetables, cereals, meat, and fish [2; 4; 5]. The management of by-products from the food industry is very diverse and closely related to the progress in science and technology [2]. Sustainable food production is becoming a contemporary priority, one where the effective and recent use of food processing by-products has begun to play a key role [6]. The actions taken are consistent with the implementation of sustainable development goal (SDG) 12, which focuses on ensuring sustainable consumption and production patterns. Sustainable resource management and the reduction of food waste are key elements of this goal. The use of sea buckthorn pomace in bread production not only contributes to waste reduction but also promotes a circular economy, responding to the needs of a sustainable food industry and conscious consumers [7; 8]. Some of these products, particularly those originating from plants, serve as valuable sources of biologically active compounds and have the potential to enhance traditional food products like bread, endowing them with health-promoting properties [4; 9; 10; 11; 12]. Bread can be enriched by adding synthetic nutrients or by adding natural raw materials. However, the latter is a much more rational way of meeting the criteria of sustainable production and consumption, especially when adding nutritionally valuable by-products. Bread and other bakery products currently constitute approximately 70% of all cereal processing products in the Polish diet [13]. Wheat and rye flour are mainly used to produce bread. Rye flour (white and whole meal) is commonly used as the main ingredient for the preparation of sourdough bread [14]. Due to the fact that bread (despite the decline in consumption) is still widely consumed, its quality should be as high as possible. Its quality should also always correspond with the important role it plays in human nutrition--as an important source of energy and in building and regulating nutritious components. Obtaining high-quality bread, with a high nutritional value, largely depends on the raw materials used for its production--both basic materials and enriching additives (especially those with a high content of biologically active substances). One such raw material, which has great potential as a valuable functional additive in bread production, may be sea buckthorn fruit pomace, a by-product created during the production process of sea buckthorn juice and oil [15; 16; 17]. Sea buckthorn is a plant whose biologically active components are concentrated in fruits, bark, roots, leaves, and flowers [18]. All of the above-mentioned morphological parts are used by the pharmaceutical, cosmetic, and food industries; however, the fruits are most widely used [16].