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

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:CaCl 2 (3:6:1) were prepared. Viscosity ( η ), conductivity ( σ ), activation energy of viscous flow ( E η ) and conduction ( E ᴧ ), transverse relaxation time (T 2 ), thermal behaviours, and anti-freezing capacities of the NADESs were investigated. A critical T 2 of 24.60 ms for η changes was obtained, and the relationship between η and T 2 was determined as ln η  = -1.398lnT 2  + 10.688. Differential   scanning   calorimetry 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 E η (41.58 ∼ 45.72 kJ mol −1 ) and E ᴧ (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.