# Innovations in Wheat Bread: Using Food Industry By-Products for Better Quality and Nutrition
## 4 Head Quality
### Baking Properties
The amount of introduced component significantly influences the extent of bread volume and crumb porosity reduction. High-dietary-fiber ingredients, such as grape pomace, may extract water from starch granules and protein networks, potentially leading to a decrease in the volume of the bread. Research by [PERSON] et al. [20] additionally indicates that the decrease in the volume and specific volume of bread may be attributed to a reduction in pH. Acidic conditions could provide a more stressful environment, thus reducing yeast activity. Moreover, acidic conditions could promote the solubilization of gluten proteins, leading to the instability of the gluten network. It can be hypothesized that the decrease in yeast activity and instability of the gluten network may be the cause of poorer crumb porosity. Regarding apple pomace, a 2% addition of this by-product from apples obtained during the cooking process does not result in a significant reduction in specific volume; however, a decrease in loaf volume is observed. Studies also show that thermal processing of apple pomace allows for a reduction in its negative impact on crumb porosity [117]. Significant reductions in specific volume were observed for bread supplemented with 5% apple pomace (AP) without and after enzymatic hydrolysis (variants hydrolyzed with Viscozyme(r) L, Pectinex(r) Ultra Tropical, and Celluclast(r) 1.5 L preparations) [124]. Researchers explain that the reduction in volume is caused by polysaccharides, which influence changes in the secondary structure of gluten proteins by altering the conformation of disulfide bridges and may partially dehydrate the gluten network through competitive water binding [125]. Natural apple pomace and those subjected to the mentioned enzymatic hydrolysis [124] resulted in a reduction in porosity from 80.06% to 70.71%. Only the variant of wheat bread prepared with apple pomace enzymatically hydrolyzed with Celluclast(r) 1.5 L did not differ significantly in terms of porosity from the control bread. Moreover, it exhibited better porosity than bread with pomace without hydrolysis. Literature analysis does not provide a clear determination of the influence of oil industry by-products from flaxseed or olives on the specific volume and porosity of wheat bread. As reported by [PERSON] et al. [17], an increase in the addition of flaxseed cake (from 5% to 15%) results in a decrease in the specific volume of bread; however, significant changes were noted with supplementation at levels of 10% and 15%. Supplementation of bread with flaxseed cake also led to a significant decrease in crumb porosity. The study indicated a porosity change from 77.7% for control bread to 70.3% for bread with a 15% addition of flaxseed cake. However, there are reports that contradict the negative effect of flaxseed cake on bread volume and porosity. For instance, [PERSON] et al. [126] observed a positive impact of flaxseed residue on specific volume with additions of 4% and 8%, especially at lower levels. The increase in specific volume compared to the control sample was 60% and 18%, respectively. Changes in dough strength and increased susceptibility to deformation due to the introduced flaxseed component explain this effect. A positive effect of incorporating flaxseed residue into bread was also observed by [PERSON] et al. [115], especially in the case of high-yield bread production with a high addition of flaxseed residue (at 25%). Lower levels of supplementation did not significantly affect the porosity of such bread. Regarding olive pomace, data revealed by [PERSON] et al. [18] showed that the introduction of olive pomace (from 5% to 15%) into flathead results in a significant reduction in bread volume. Additionally, as shown, partial replacement of wheat flour with olive pomace leads to a reduction in gluten content, disruption of the gluten network, weakening of the dough structure, and consequently, a decrease not only in volume but also in crumb porosity was observed.