Effect of Olive Pomace on the Nutritional, Technological, and Sensory Properties of Gluten-Free Sourdough Bread

Olive pomace (OP), a by-product of olive oil extraction consisting of seed fragments, pulp residues, peels, and water, is an underutilised source of bioactive compounds with potential applications for improving the nutritional quality of gluten-free foods. This study investigated the effects of OP addition on the nutritional composition, antioxidant compounds, technological properties, and sensory quality of gluten-free sourdough bread. Rice flour, OP, and breads containing 0%, 5%, 10%, 15%, 20%, 25%, and 30% OP were analysed for protein, lipids, ash, soluble and insoluble dietary fibre, free phenolics, tocols, and carotenoids. Technological characteristics, colour, and sensory quality were also assessed. OP contained higher levels of most analysed compounds than rice flour. Consequently, enrichment improved the nutritional composition of the breads. Protein content decreased slightly (from 10.41 to 10.03 g/100 g DM), but lipid and ash contents increased from 1.47 and 1.31 g/100 g DM in the control to 4.84 and 3.85 g/100 g DM in bread containing 30% OP. Soluble, insoluble, and total dietary fibre increased from 0.54, 3.15, and 3.69 g/100 g DM to 1.94, 13.70, and 15.64 g/100 g DM, respectively. Phenolic content rose from 10.8 to 227.4 mg/kg DM, tocols content increased from 38.9 to 58.2 mg/kg DM, whilecarotenoids made a minimal contribution. Enriched breads exhibited lower volume and greater firmness than the control, whereas bread containing 20% OP achieved the best sensory characteristics. These findings highlight OP as a promising ingredient for valorising olive oil processing by-products while enhancing the nutritional quality of gluten-free sourdough bread.