Development of Skimmed Goat Milk Functional Ingredient Enriched with Grape Pomace Seed and Agrocybe aegerita Extracts: Optimization, Characterization and Application in Dehydrated Foods

The aim of this study was to formulate and optimize a novel functional ingredient based on thermally treated skimmed goat milk enriched with Agrocybe aegerita mushroom extract (ME) and grape pomace seed extract (GPE), intended for application in a dehydrated soup model. A central composite design was applied for preliminary optimization and the formulation based on antioxidant properties. The optimized ingredient exhibited enhanced antioxidant activity, with GPE identified as the dominant factor influencing the responses. However, deviations between predicted and experimental values were observed, reflecting moderate model fitting and differences in assay mechanisms. ATR-FTIR spectra were dominated by milk compounds, while DLS and electrophoretic analysis revealed structural modifications, including polymodal particle size distribution and alterations in the protein profile, indicating interactions between milk proteins, polyphenols, and mushroom-derived compounds. UHPLC-QToF-MS analysis confirmed a high content of grape-derived phenolic compounds. Following simulated gastrointestinal digestion, several phenolic compounds were detected in the soluble fraction, with catechin and ethyl gallate exhibiting the highest bioaccessibility (12.58% and 4.54%). The enriched ingredient showed modified techno-functional properties, including reduced emulsifying capacity but improved foaming behavior, which was attributed to protein structural changes and intermolecular interactions. Application in a dehydrated soup model demonstrated good solubility, stability, and high sensory acceptability without negative effects on flavor. Furthermore, the enriched soup showed enhanced antioxidant properties after simulated gastrointestinal digestion. The developed formulation represents a promising natural functional ingredient, combining enhanced bioactive properties with satisfactory technological performance.