Effect of different leavening agents on the nutritional characteristics of two durum wheat breads

Two durum wheat bread samples produced using the same re-milled semolina but different leavening agents (sourdough and compressed yeast) have been considered in this study. Chemical composition, color characteristics, lutein content and starch digestibility have been addressed in both samples. In addition, to evaluate possible modifications induced on the protein structure attributable to the different leavening agents used, the secondary structure of proteins was also studied by Fourier transform infrared spectroscopy. The crumb of bread sample produced by compressed yeast exhibited a higher yellow index compared to the other sample but this difference was completely lost in crust because of the high baking temperature applied. Lutein resulted more preserved after the yeast fermentation due to the shorter time required for the fermentation with respect to sourdough. Total starch and resistant starch content resulted comparable in the two samples with the latter about 1% in both samples. The infrared spectroscopic study of the protein amide I band showed the lack of the random coil structure, related to the protein denaturation, and negligible changes in the relative ratios among the alpha-helix, beta-sheet and beta-turn secondary structures of proteins.