Subcritical Water Extraction of Phenolic Compounds from Onion Skin Wastes (Allium cepa cv. Horcal): Effect of Temperature and Solvent Properties
1. Introduction Subcritical water extraction (SWE) has emerged as a powerful green-technology approach for recovering high-value phytochemicals from agro-industrial residues. Onion skins, often discarded as waste, are exceptionally rich in phenolic compounds such as quercetin and its derivatives, which exhibit strong antioxidant, anti-inflammatory, and antimicrobial properties. This study explores how temperature and solvent characteristics affect the extraction yield and chemical profile during SWE of Allium cepa cv. Horcal onion skins. By investigating these relationships, researchers aim to optimize sustainable extraction strategies capable of transforming agricultural waste into valuable raw materials for the food, cosmetic, and nutraceutical industries. 2. Influence of Temperature on Phenolic Yield Temperature is a critical factor in subcritical water extraction due to its strong influence on water’s dielectric constant, diffusivity, and solvation behavior. As temperatur...