Cloud Point Extraction of Chlorophylls from Spinach Leaves Using Aqueous Solutions of Nonionic Surfactants

Chlorophylls and their derivatives are currently used in a wide range of applications. To replace the volatile organic solvents commonly applied for their extraction from biomass, aqueous solutions of nonionic surfactants are studied herein in the extraction of chlorophylls from spinach leaves. Aqueous solutions of a wide range of nonionic surfactants were investigated, allowing us to demonstrate the relevance of their hydrophilic-lipophilic balance (HLB) on the extraction performance and chlorophylls a/b selectivity, with the best results obtained with surfactants with a HLB ranging between 10 and 13. Furthermore, it was found a relevant impact of the surfactants aqueous solutions toward the biomass disruption, demonstrating that changes in the biomass structure allow a better access of the solvent to the target compounds embedded in the biopolymer matrix. A response surface methodology was then used to optimize operational conditions (surfactant concentration, solid-liquid ratio, and temperature), leading to a maximum extraction yield of chlorophylls of 0.94 mg/g. After the extraction step, the chlorophylls-rich extract was concentrated by heating above the surfactant-water cloud point, leading to a separation into two phases and to a concentration factor of 9 and a recovery of 97% of chlorophylls in the surfactant-rich phase. The antioxidant activity of the extracts was finally appraised, showing that the antioxidant activity of the aqueous chlorophylls-rich extracts is higher than that obtained with volatile organic solvents. The obtained results show the potential of aqueous solutions of nonionic surfactants to extract highly hydrophobic compounds from biomass and their potential for a direct use in cosmetic and nutraceutical applications, without requiring an additional recovery or purification step.