Ultrasound-Treated Sweet Potato Peel Enhances Nutritional Quality and Antioxidant Potential of Gluten-Free Brownies: A Metabolomics and Cell-Based Approach

Agri-food by-products such as sweet potato peel (SP) represent a sustainable and valuable source of bioactive compounds for improving gluten-free (GF) foods. This study evaluated the nutritional and functional impact of incorporating SP at 8% and 16%, either untreated or ultrasound-assisted extraction (UAE)-treated, into GF brownies. An untargeted metabolomics approach combined with chemometrics was applied to characterize phytochemical modulation after in vitro digestion of the brownies, while antioxidant and anti-inflammatory effects were assessed using RAW264.7 macrophages. SP incorporation increased the dietary fiber (reaching a content of 7.86%) and glycosylated flavonoid content in reformulated brownies, leading to a reduction of inflammatory markers in the cellular model. Sensory evaluation showed that SP addition did not significantly affect texture-related attributes or extract-related perception. In contrast, UAE acted as an efficient extraction strategy, enhancing terpenoid-like compounds and total phenolic content (TPC), reaching values of 401.97 mg GAE 100 g−1 after 16% incorporation. Overall, combining SP valorization with UAE represents a promising strategy to develop nutritionally enhanced GF products, providing a foodomics-based framework for next-generation functional bakery products.