Valorization of Canola Leaves (Brassica napus L.) Through Sourdough Breadmaking: A Preliminary Study on Dough Rheology and Bread Quality

Canola seeds are largely used for oil extraction, while the rest of the plant, particularly the leaves, remain an underutilized yet unexplored functional food ingredient. The aim of this study is to investigate the upcycling of canola leaves powder (CL) to develop wheat bread with an increased potential nutritional value. The impact of including 5 g/100 g CL in combination with 20 g/100 g freeze-dried sourdough (flour weight basis) was investigated on the technological and nutritional properties of wheat dough and bread. Furthermore, this study aimed to evaluate the effect of sourdough acidification on starch digestibility in CL-enriched bread. Incorporation of CL and/or sourdough prolonged dough development time and reduced dough stability during mixing. GlutoPeak analysis revealed a rapid gluten aggregation when CL was incorporated. From a nutritional perspective, breads enriched with CL exhibited higher dietary fiber and total phenolic content, while sourdough incorporation lowered bread pH. The harder crumb texture resulting from CL inclusion was counteracted by the softening effect of sourdough. Image analysis further showed a finer and more homogeneous crumb structure due to leaves incorporation, characterized by increased pore density and reduced mean pore area. Regarding starch digestibility, CL showed a tendency to reduce the in vitro starch hydrolysis rate (k) and combined with the sourdough, further slowed down starch hydrolysis. Results suggest that using CL in breadmaking can be a valuable strategy to valorize this by-product within a circular economy framework.