Flax seeds are a valuable raw material for the production of functional bakery products. The article investigates the fermentation processes in wheat dough supplemented with whole and crushed flax seeds in dry and soaked states. For a holistic understanding of the fermentation process, the regularities of the kinetics and dynamics of gas formation in the experimental samples were analyzed. It was found that during fermentation in samples with whole flax seeds in dry and soaked states, the amount of carbon dioxide released slightly increases compared to the control. In the samples with crushed dry and soaked flax seeds, the total amount of carbon dioxide released is higher than in the control sample by 16.5% and 19.0%, respectively. In the sample with crushed flax seeds, the nature of the dynamics of carbon dioxide release differs from the control sample, namely, a one-stage fermentation is observed. At the same time, the peak of carbon dioxide release was observed almost 30 minutes later than in the control sample. This may be due to the fact that soaking flaxseed products produces viscous solutions of polysaccharides, which envelop the yeast cells during dough kneading and slow down the supply of nutrients to them. Based on the analysis of the dynamics of carbon dioxide emission, it is recommended to reduce the duration of dough fermentation for the sample with whole flax seeds to 90 minutes, and for the samples with crushed seeds and soaked flax products to 60 minutes, so that the most intense carbon dioxide emission in these experimental samples occurs during the period of proofing of dough pieces. It was found that the introduction of whole and crushed flax seeds in soaked form slows down the rise of the dough due to the thickening of the dough system with water-soluble and insoluble flax dietary fiber, reducing fermentation and the formation of sugars in the dough system.