Influence of Leavening Agent on the Stability of Bioactive Compounds and Antioxidant Capacity of Gluten-Free Bread with Beetroot By-Product

Beetroot by-product (BBP), an industrial residue rich in bioactive compounds, offers a sustainable solution to reduce food waste while enhancing the nutritional profile. The aim of the study was to evaluate the effect of different leavening agents (baking powder and baker's yeast) and geometry (rectangular and oval) on bioactive compound stability and antioxidant capacity when incorporating beetroot by-products into gluten-free bread formulations. Rectangular and oval-shaped gluten-free breads were produced using 3D printing. Moisture content, pH, color parameters, bioactive compounds (betalains and phenolic compounds), and antioxidant activity were analyzed in both crust and crumb. BBP addition significantly increased total phenolic content, antioxidant capacity, and betalain content in all formulations. Breads with baker's yeast exhibited higher bioactive retention due to acidic pH levels that favor phenolic and betanin stability. Bread with baking powder showed a higher retention of betaxanthins (yellow pigments), while those with baker's yeast retained betacyanins (red-violet pigments). Oval geometry improved moisture retention and bioactive preservation due to reduced surface exposure. This research demonstrates the feasibility of developing nutritionally enhanced gluten-free products using additive manufacturing. Bread enriched with beetroot by-product and baker's yeast represents a suitable option to improve functionality and pigment retention while valorizing industrial waste.