## 1 Introduction  
Flaxseed is known for its health-promoting properties. Its consumption exerts a beneficial effect on lowering blood levels of cholesterol and glucose and prevents atherosclerosis and other cardiovascular diseases (CVD) [1, 2]. Until recently, this effect has been ascribed to the consumption of oil contained in flaxseeds, in particular to the properties of its essential unsaturated fatty acids (EFAs). Currently, however, many authors have confirmed that the best health-promoting effects are achieved upon the intake of lignans contained in the flaxseed fiber, including mainly seciosolaricinesinol occurring in the form of seciosolaricinesinol diglycoside (SDG) [2, 3]. Administering flax pomace to persons with hypertension at a dose of 30 g/day for a few months has been shown not only to reduce blood cholesterol level and blood pressure but also to minimize the risk of CVD development. A similar effect was obtained when consuming whole flaxseeds [1, 4, 5]. At the same time, patients consuming flaxseed pomace provided themselves with a lower amount of calories in their diet compared to the patients consuming whole seeds, which additionally allowed for an effective fight against obesity. Golden flaxseed pomace, which is the residue of industrial oil extraction, is no longer an unmanaged waste product. Due to its valuable nutritional value, it has been used as an enriching additive to many food products (e.g., as an ingredient in breadcrumbs and additive to bread, cookies, and muffins) [1, 3, 6, 7, 8, 9]. Different is the case of pomace obtained from common flaxseed. Although it has more fiber and health-promoting components compared to golden flaxseed pomace, it is not used in the industry and is still treated as waste, at best used as animal feedstuff [10; 11]. The few studies that have attempted to use this waste as a component for enriching food products with fiber have clearly indicated that the dark color imparted to food products by even a small addition of flaxseed pomace discouraged potential customers and completely disqualified products on the market [6; 12]. It should be noted that consumer acceptance surveys of functional foods have shown that consumers are generally not willing to compromise on the taste and appearance of foods despite their health benefits [9; 13; 14; 15]. This has been confirmed by our previous research, which proved that the organoleptic assessment of products with common flaxseed pomace (dark color) was lower than of those with the addition of golden flaxseed pomace [6]. Analyzing in detail the data obtained in previous works, it was found that the disqualifying effect was due to the change of color of these products, as there were no statistically significant differences between any of the examined characteristics of products made with the addition of common flaxseed and golden flaxseed, except for their color. The color of the snacks with the addition of common flaxseed was rated much lower compared to the golden flaxseed snacks. This effect was clear even with small additions of the pomace [6]. In this study, it was hypothesized that it is possible to change the consumer's views on the color of products with the addition of common flaxseed pomace. Consumer surveys have confirmed that the dark color disqualifies a food product only if the consumer expects it to have a bright color. However, there is a range of products whose dark color does not deter customers, e.g., cocoa. Consumers accept the darker color of chocolate-flavored corn snacks. The dark color is even desired by consumers in such products because--in their opinion--it is tantamount to a high cocoa content. It can, therefore, be assumed that the color of extrudates produced with the addition of common flaxseed pomace will not disqualify them when presented to consumers as a chocolate-flavored snack. It is likely that the color of products with the addition of common flaxseed will be effectively masked with dark color of the cocoa.