Multifunctional sodium alginate-based self-healing edible cross-linked coating for banana preservation

Edible coating plays an important role in preventing fruit rot and prolonging the shelf life of fruit. However, a large amount of water will accumulate on the surface of the fruit through respiratory metabolism during storage, leading to the dissolution of the coating. Therefore, it is important to develop water-resistant coatings to extend the shelf life of bananas. In this work, gluconolactone (GDL) was used to slowly generate gluconic acid, which protonated the amino groups of the whey protein isolate (WPI) and enhanced the electrostatic interaction between WPI and sodium alginate (SA) to form a cross-linked composite coating. The introduction of WPI increased the water contact angle value of the films from 47.1° to 102.1°. The composite coating exhibited excellent mechanical properties, water resistance, UV shielding self-healing, and gas-selective transmission. The experiment of banana preservation proved that the composite coating could effectively slow down the water loss of bananas, retard the ripening and browning, and extend the shelf life of bananas for 6 days at 25 °C and 50% RH. Therefore, this multifunctional coating has important reference value for the design of self-healing coating, and shows good potential in the preservation of perishable fruits.