Production of Protein-Rich and Cannabinoid-Free Extracts from Industrial Hemp by Combined Solvent-Free Ultrasound- and Microwave-Assisted Extraction

Protein-rich cannabinoid-free extracts were prepared from hemp (Cannabis sativa L.) inflorescences using an ultrasound probe system and an ultrasound-microwave extractor. The cannabinoid content was evaluated by liquid chromatography-diode array detection-mass spectrometry (LC-DAD-MSn) analysis, assessing tetrahydrocannabinol (THC)’s non-detectability in most of the extracts and hemp residues. Extract characterization through a Leco nitrogen analyzer and by liquid chromatography-tandem mass spectrometry (LC-MS/MS) analysis highlighted a higher protein content and interesting profile with respect to untreated hemp. Ultrahigh-performance liquid chromatography-fluorescence detection (UHPLC-FLD) analysis on the most promising extracts quantified all the flavor active free amino acids, with “umami” taste-rich glutamic acid as the most abundant one. In this regard, according to the hierarchical cluster and principal component analysis, the ultrasound technique was the most influential factor. The outcomes of this study support the use of cannabinoid-free hemp inflorescence extracts obtained by sustainable processes as novel vegetal protein sources.