Preparation and characteristics of sodium caseinate/zein composite coating and its application effect on inhibiting the rancidity of peanut chunks

Sodium caseinate (CN) and zein were used as raw materials to prepare a composite coating applied in air system with mechanical properties, and water vapor and oxygen permeability as evaluation index. Results showed the most suitable conditions were the mass ratio of CN to zein at 0.25: 1, 60% (v/v) aqueous ethanol, polyethylene glycol (0.3 g/g) as the plasticizer, and citric acid (2.5%, w/v) as the crosslinker, and curing temperature at 50 ˚C. Under these conditions, the tensile strength of composite coating was 6.671 MPa, and the elongation at break was 97.596%. The water vapor permeability was 14.236 g·mm/(m 2 ·d·kPa), and the growth rate of peroxide value of tung oils sealed by the composite coating was 71.300%. Results from Fourier transform infrared spectroscopy, atomic force microscopy, scanning electron microscopy, and differential scanning calorimetry revealed that CN and zein were effectively crosslinked by citric acid with improved compatibility and smoother surface of the resulting coating. Results from the accelerated oxidation experiment showed that coating reduced the peroxide value and p-anisidine value of peanut chunks from 1.02 g/100 g and 6.59 to 0.62 g/100 g and 2.24, respectively, indicating that the composite coating prepared effectively inhibited the oxidative rancidity of peanut chunks. • Sodium caseinate and zein coating were prepared with citric acid as crosslinker. • Tensile strength and elongation at break of the coating were 6.671 MPa and 97.596%. • Water vapor permeability of the coating was 14.236 g·mm/(m 2 ·d·kPa). • Growth rate of peroxide value of tung oils sealed by the coating was 71.3%. • Coated peanut chunks had lower peroxide value and p -anisidine than uncoated ones.