Development of natural deep eutectic solvents (NADESs) as anti-freezing agents for the frozen food industry: Water-tailoring effects, anti-freezing mechanisms and applications

Abstract

Nature-inspired natural deep eutectic solvents (NADESs) as anti-freezing agents including Pro:Glc (5:3), Pro:Glc (1:1), Pro:Sor (1:1), and Urea:Glc:CaCl2 (3:6:1) were prepared. Viscosity (η), conductivity (σ), activation energy of viscous flow (Eη) and conduction (Eᴧ), transverse relaxation time (T2), thermal behaviours, and anti-freezing capacities of the NADESs were investigated. A critical T2 of 24.60 ms for η changes was obtained, and the relationship between η and T2 was determined as lnη = -1.398lnT2 + 10.688. Differentialscanningcalorimetry and low-field nuclear magnetic resonance analyses indicated NADESs could hinder the molecular motion as temperature decreased through enhancing the hydrogen-bonding strength, endowing them with excellent anti-freezing capacity. NADESs showed varied Eη (41.58 ∼ 45.72 kJ mol−1) and Eᴧ (48.31 ∼ 63.08 kJ mol−1), of which Pro:Sor (1:1) possessed the greatest ones, showing its greatest temperature sensitivity and best anti-frosting capacity. Applications in frozen chicken breast further announced the potentials of NADESs as anti-freezing agents for the industry.