Enhancing the Antioxidant and Nutritional Profile of Gluten-Free Sourdough Bread Using Hemp Press Cake Meal

Food industries produce large amounts of by-products, valuable sources of bioactive compounds that can enhance gluten-free foods. This study evaluated the effect of hemp cake meal (HC) addition on the antioxidant, nutritional, technological, and sensorial properties of gluten-free sourdough breads. Rice flour, HC, and breads with increasing HC levels (0–30%) were analysed for ash, protein, lipids, soluble and insoluble fibre, phenols, tocols, and carotenoids. Technological traits, colour, and sensory quality were also assessed. HC showed higher contents of most compounds than rice flour. As a result, enriched breads displayed marked nutritional improvements: protein increased from 8.9 g/100 g (control) to 17.6 g/100 g (30% HC), lipids from 1.5 to 3.9 g/100 g, soluble fibre from 0.54 to 1.27 g/100 g, insoluble fibre from 3.2 to 13.4 g/100 g, and phenolics (mainly ellagic and rosmarinic acids, and caffeic and naringenin derivatives) from 10.8 to 174.8 mg/100 g. Tocols and carotenoids, though scarce, slightly increased. However, HC-enriched breads had lower volumes and a firmer, stickier texture. Nevertheless, up to 10% HC inclusion did not affect appearance, aroma, texture, or taste. Therefore, a moderate HC addition can improve antioxidants and the nutritional quality of gluten-free sourdough breads while maintaining a good sensory acceptability.