Microwave-Assisted Subcritical Water Extraction of Hemp Seeds for the Simultaneous Recovery of Proteins and Phenolic Compounds

This work presents an innovative microwave-assisted subcritical water extraction (MA-SWE) approach for the simultaneous recovery of proteins and phenolic compounds from hemp seeds (HS). The extraction temperature (100–180 °C), time (5–60 min), and solid-to-liquid ratio (1:5–1:30 w/v) were optimized via Box–Behnken design. The effects of whole, crushed and defatted HS were investigated, with defatted HS exhibiting higher selectivity for proteins and polyphenols. Two optimization strategies were explored: one maximizing protein and polyphenol yields and another minimizing solvent and energy consumption, while maintaining competitive yields. The maximized conditions (MAPPY) were 180 °C, 57 min, and a ratio of 1:28, providing a protein selectivity of 48.91 g/100 g of dry extract (DE) and a total phenolic content of 7.24 g gallic acid equivalent/100 g DE. Regarding functional properties, both strategies yielded extracts with similar performance; however, the maximization strategy resulted in higher emulsifying capacities. These results support the industrial valorization of defatted HS by MA-SWE under optimized conditions to produce antioxidant- and protein-rich ingredients.