## 4 Discussion
evaluated the use of encapsulated n-3 fatty acids for bread fortification as their degradation during storage time has proven to decrease, although negative changes in the texture and color of bread have been also observed during storage [82]. Besides, we must consider that the extent of lipid degradation in these products is usually determined by peroxide value measurements, but this could not give a reliable answer, as peroxides may be subjected to further degradation. In this context, more complete information regarding the oxidative stability during storage should be therefore obtained, and the study of the best storage conditions to preserve the quality of the product, according to the percentage of flaxseed cake and the different leavening agent used, is currently in progress. Sourdough has a long tradition and is largely used as a leavening agent since it provides many technological advantages and higher overall quality compared to baker's yeast [83; 84]. The complex microflora characterizing sourdough includes several strains of both yeasts and LAB and is deeply influenced by both endogenous factors such as raw material composition (carbohydrates, nitrogen sources, minerals, lipids, free fatty acids, and enzyme activities) and exogenous factors such as process parameters (temperature, dough yield, fermentation time, and refreshment procedure) [13; 84]. Many properties of sourdough are related to the metabolites produced by resident LAB (organic acids, exopolysaccharideacharides (EPS), enzymes, bactericidal and antimicrobial compounds). To the best of our knowledge, the effect of flaxseed cake fortification as a function of the leavening agents adopted has not yet been investigated. In this context, our findings showed that the leavening agent was able to affect the levels of health-promoting nutraceutical compounds, with an improvement of phenols, flavonoids, and TEAC in sourdough breads, as already reported for various legumes and pseudo-cereals used for the fortification of bakery products [61; 85]. These interesting and beneficial properties, here highlighted, are added to others that are well known and related to the use of sourdough in breadmaking [4; 40; 41], such as the ability to improve the final product shelf life thanks to its acidity [86], as well as the antifungal [87] and antimicrobial activity [88]. Moreover, in our experience, the leavening agent significantly affected both the organoleptic expression and the aroma profile of the fortified bread at different levels of flaxseed concentration. As in many other areas of food processing, the challenge in fortified cereal food lies in the ability to combine nutritional and health benefits with good sensory quality. In the experimental conditions here adopted, it was possible to select the best recipe in terms of percentage of flaxseed cake added to the flour mix as a function of leavening agent utilized (5% and 7.5% when sourdough and baker's yeast were used respectively). Based on this evidence, once the preferred quality levels of both the nutritional and organoleptic profile of the fortified bread are guaranteed to the consumers, the bakers will be able to choose the leavening system (soundough versus baker's yeast) best suited to their production needs simply by varying the percentage of flaxseed cake added to the recipe. The following are available online at [[http://www.mdpi.com/2076-3417/10/15/5235/s1](http://www.mdpi.com/2076-3417/10/15/5235/s1)]([http://www.mdpi.com/2076-3417/10/15/5235/s1](http://www.mdpi.com/2076-3417/10/15/5235/s1)), Table S1: Complete headspace compositions of cooked breads (w = whole or s = sliced) as a function of flaxseed percentage and leavening agent used. Data reported in italics were already published in [PERSON] et al., 2020 [39]. Conceptualization, C.S., F.V., L.G.A. ; methodology, C.S., F.V. ; validation, C.S., F.V, S.T. and I.T. ; formal analysis, I.T., A.S., S.T. and G.F.; investigation, I.T., G.C. and G.F.; resources, I.T. and C.S. ; data curation, M.M. and A.Z.