Structure and properties of moisture-resistant konjac glucomannan films coated with shellac/stearic acid coating

• The edible coated films show potential application in food preservation.
• The moisture barrier efficiency of the coated film is comparable to that of PE film.
• The thickness of the films, with coating layer of about 10 μm, is less than 40 μm.
• Shellac and stearic acid play different roles in enhancing properties of the films.
• The coating also makes filter paper hydrophobic (water contact angle achieved to 100°).

A series of moisture-resistant konjac glucomannan films were prepared by coating shellac/stearic acid emulsion on deacetylated konjac glucomannan films (dKGM). The effect of stearic acid content on structure and properties of the coated films were investigated by field emission scanning electron microscopy (FE SEM), Fourier transform infrared spectroscopy (FT-IR), ultraviolet spectroscopy (UV), water vapor permeability (WVP), water uptake, water contact angle, and tensile testing. The results revealed that shellac in the coating adhered intimately to the surface of dKGM film, and provided a substrate for the dispersion of stearic acid which played an important role in enhancement of the moisture barrier properties and mechanical properties of the coated films. The WVP of the coated films decreased from 2.63 × 10−11 to 0.37 × 10−11g/(m s Pa) and the water contact angle increased from 68° to 101.2° when stearic acid content increased from 0 wt% to 40 wt%, showing the potential applications in food preservation.