## 3 Results and Discussion
### Composition and Physical Properties of Bread  
Bread enrichment is aimed at improving its nutritional properties and supplementing the diet with bioactive compounds. However, changes made to the formulation should not adversely affect the other properties of the bread, including its sensory acceptability. One method of bread enrichment is the introduction of vegetable raw materials into the recipe, which enrich the bread mainly with dietary fiber and bioactive compounds [34; 36; 37; 38]. The protein content in the control bread was 9.76 g/100 g, which confirms previous observations regarding various types of bread [3]. The highest 10% share of lyophilized kale resulted in a non-significant (\(p>0.05\)) increase in protein content to 10.12 g/100 g. The lack of significant effect on the content of this component is due to the fact that wheat flour itself contains a significant amount of protein. The content of dietary fiber in the control bread was 2.62 g/100 g, including 0.93 g/100 g of the soluble fraction and 1.69 g/100 g of the insoluble fraction. The data obtained are slightly lower than the values reported for various types of bread by [PERSON] et al. [3]. The addition of kale lyophilate resulted in a significant (\(p<0.05\)) increase in the content of dietary fiber and its fractions. In the bread containing 10% of kale, 3.77 g of fiber per 100 g was found, including 1.14 g/100 g of the soluble fraction and 2.63 g/100 g of the insoluble fraction. The control bread analyzed had a relatively low content of total polyphenols at 7.16 mg/100 g due to their low content in wheat flour [39]. The addition of 5% and 10% lyophilized kale resulted in a significant (\(p<0.05\)) increase in total polyphenol content to 48.87 mg/100 g and 87.44 mg/100 g, respectively. This confirms the previous observations concerning the possibility of enriching bread with polyphenols through the addition of raw vegetable materials. The essential parameter characterizing the bread and providing an opportunity to assess the influence of the recipe composition is the volume and specific volume of the loaves. Figure 3: Creep and recovery curves of control dough and samples with kale powder at different concentrations. The data summarized in Table 2 indicate that the lyophilized kale addition caused a small and non-significant (_p_ > 0.05) decrease in the volume and specific volume of the bread. The available literature data indicate that replacing wheat flour with other ingredients, including lyophilized vegetables, can result in a decrease in loaf volume [37]. In turn, [PERSON] et al. [34], who enriched bread with celery powder, obtained similar results. [PERSON] et al. [40] found a decrease in bread volume when vegetable pastes were introduced into the recipe. Also, [PERSON] et al. [38] observed a decrease in the specific weight of bread enriched with a broccoli-based preparation. In a study by [PERSON] et al. [35] and [PERSON] et al. [41], the addition of mesquite flour to wheat dough resulted in a decrease in bread volume because the presence of mesquite interfered with the formation of the bread structure by weakening the gluten network. [PERSON] et al. [42] enriched bread with pumpkin powder, observing an increase in volume at lower doses of this ingredient and a decrease in volume at higher doses. The addition of lyophilized kale to the dough resulted in some changes in the crumb structure, as reflected in the values of parameters determined by digital image analysis (Table 2). The presence of lyophilized kale caused a significant (_p_ = 0.008) reduction in average pore diameter in comparison with the control bread, while the amount of kale was not significant. There was also a decrease in porosity, but the differences were non-significant (_p_ > 0.05). In contrast, a significant (_p_ = 0.021) increase in pore density with a simultaneous significant (_p_ = 0.004) decrease in the number of large pores (>5 mm\({}^{2}\)) was observed for bread with a higher addition of lyophilized kale.