Beeswax coating improves the hydrophobicity of sodium alginate/ anthocyanin/ cellulose nanocrystal indicator film

This study investigates the waterproof layer formed by beeswax (BW) to improve the hydrophobicity of sodium alginate/black soybean seed coat anthocyanin/cellulose nanocrystal indicator films. The concentrations of BW and the fabrication method of the waterproof layer, including spraying, coating (CO), and soaking, were optimized. The results showed that the optimal concentration of BW in the waterproof layer was 5% owing to its high water contact angle of 111.5°. Different methods of fabricating waterproof layers with BW led to the formation of particles of different sizes on the microscopic film surface. Hydrophobic films with a waterproof layer of BW-CO had high transmittance and pH sensitivity, ensuring the basic properties of indicator films. Meanwhile, they exhibited excellent water barrier properties based on the water contact angle, water vapor adsorption, water vapor permeability, water content and water solubility. In particular, these films remained highly hydrophobic after 10 days of storage at 100% humidity, with a water contact angle of 108.3°. The findings indicated that hydrophobic sodium alginate/black soybean seed coat anthocyanin/cellulose nanocrystal indicator films were prepared using BW, which improved their potential application in intelligent food packaging.