# Innovations in Wheat Bread: Using Food Industry By-Products for Better Quality and Nutrition
## 6 Nutritional Value of Bread
Scientific research confirms that adding fiber to carbohydrate-rich products like bread and pasta can reduce the glycemic response [161]. According to [PERSON] et al. [17], both the addition of flax flour (FF) and flax cake (FM) at levels of 5, 10, or 15% increase the TDF content in bread in a comparable manner, ranging from 40 to 74% for FF and from 28 to 81% for FM, while the TDF content in the control bread was 7.15% d.m. These studies also demonstrated an increase in the content of individual fiber fractions, especially SDF, with up to a 2.5-fold increase in trials with a 15% addition of flax materials compared to the control. This is a highly beneficial change, as SDF is often deficient in human diets [162]. In the studies by [PERSON] et al. [17], the IDF:SDF ratio ranged from 1.79:1 for the control to as low as 0.95:1 for a 15% addition of flaxseed cake. This is mainly due to the high content of mucilage gum in flaxseed by-products, the presence of which is very beneficial due to its proven health-promoting effects [93]. Due to the increased dietary fiber content in the bread, the overall carbohydrate content decreased [17]. By-products from oilseed processing such as flaxseed, unlike that from fruit processing, not only serves as a good source of dietary fiber but also provides a very good source of protein. The increase in protein content in bread supplemented with flaxseed by-products is confirmed by studies conducted by [PERSON] et al. [126] and [PERSON] et al. [17]. The addition of flaxseed residue (FR) at levels of 5 or 10% increased the protein content from 11.23% d.m. for the control to 11.66% d.m. and 12.27% d.m. respectively [126]. In the studies by [PERSON] et al. [17], this increase ranged from 13.36% d.m. for the control to 16.3% d.m. for a 15% addition of flax cake and 16.88% d.m. for a 15% addition of flax flour, representing an increase of 22% and 26% respectively compared to the control. Due to the high fat content remaining in the flaxseed residues, an expected increase in the fat content of supplemented bread was achieved. In the study by [PERSON] et al. [17], the increase in lipid content was higher in bread supplemented with flax flour than flax cake, due to the initial fat content in the raw material. The lipid content in bread with a 15% addition of FM increased to 0.95% dry matter (d.m. ), while the content of this macronutrient in the control bread was 0.18% d.m. On the other hand, a 15% addition of FF increased this level to 1.62% (a 9-fold increase). According to [PERSON] et al. [95] and [PERSON] et al. [14], in sourdough or yeast bread supplemented with 5, 7.5, or 10% flaxseed cake flour relative to the dough mass, the content of unsaturated fatty acids such as linolenic acid increased (5.19-6.52-fold increase for sourdough bread and 2.93-5.94-fold increase for yeast bread) as well as oleic acid (1-41% increase for sourdough bread and 40-300% for yeast bread). A decrease in the content of fatty acids such as palmitic and linoleic acid was also noted. The same authors also indicate that in fortified bread, the overall content of PUFA n-3 and MUFA increased, while SFA and PUFA n-6 decreased. Notably, there was an improvement in the ratio of n-3 to n-6 fatty acids from 17.64 for control yeast bread and 16.81 for control sourdough bread to as low as 1.69 and 1.89, respectively, with 10% supplementation. This carries health benefits due to the proven role of n-3 acids in preventing cardiovascular and nervous system diseases [163]. The total phenol content in sourdough and yeast bread with 5-10% supplementation of flaxseed cake flour increased in direct proportion to the level of addition, with a predominance for yeast bread (from 0.301 mg GAE/g d.m. for CON to 1.212 mg GAE/g d.m. at 10% fortification). A similar trend was observed for the flavonoid content expressed as catechin equivalents (increase of 1.98-2.9 times in sourdough bread and 2.44-4.04 times in yeast bread) [14; 95].