Deep eutectic solvents in plant-based protein extraction: Limitations and applications

Plant proteins have gained considerable attention as sustainable alternatives to animal-derived proteins. However, efficient and environmentally friendly extraction methods remain a major challenge. Conventional alkaline extraction techniques often lead to protein denaturation, high energy consumption, and the generation of large volumes of wastewater. Recently, deep eutectic solvents (DES) have emerged as promising green solvents for plant protein extraction due to their biodegradability, low toxicity, tunable physicochemical properties, and high extraction efficiency. This review provides a comprehensive overview of DES-based systems for extracting proteins from diverse plant sources, including legumes, cereals, oilseeds, microalgae, and agro-industrial by-products. The composition, formation mechanism, advantages, and limitations of DES systems are discussed, along with their influence on protein yield, structural integrity, amino acid composition, and techno-functional properties. Recent studies demonstrate that DES extraction generally preserves protein secondary structures, improves solubility, emulsifying capacity, foaming ability, and thermal stability, and reduces co-extraction of undesirable compounds. In addition, DES systems can be combined with emerging technologies such as microwave, ultrasound, and enzymatic treatments to further enhance extraction efficiency. Despite challenges such as high viscosity and recovery optimization, DES-based extraction represents a sustainable and versatile approach for producing high-quality plant protein ingredients for food, pharmaceutical, and biotechnological applications.