Exploring the use of acorn flour in gluten-free bread applications: product quality and in vitro starch digestibility

As a sustainable ingredient, acorn flour supports biodiversity and reduces dependence on conventional grains, promoting eco-friendly gluten-free (GF) food production. This study investigated the incorporation of increasing levels of Quercus robur acorn flour in GF bread formulation and evaluated its effect on the physico-chemical and nutritional attributes of the product. Water content for each bread formulation was empirically optimized to obtain the largest loaf expansion and softest crumb. Optimized acorn-enriched GF breads were characterized for specific volume, crumb hardness, moisture and total (poly)phenolic contents, antioxidant activity, and in vitro starch digestibility. From a technological perspective, acorn flour was successfully integrated into GF bread, with water content modulation playing a key role in optimizing bread volume and texture. The recommended substitution level was below 30% to maintain desirable texture and structural characteristics. From a nutritional standpoint, acorn flour incorporation significantly increased dietary fiber, resistant and slowly digestible starch contents, while antioxidant activity was significantly enhanced at acorn flour inclusion levels of 10% or higher. These findings corroborate Quercus robur acorn flour as a valuable ingredient for improving the nutritional profile of gluten-free bread.