Properties of an active film based on chitosan/silk fibroin loaded with an essential oil microemulsion and its application in preservation of strawberries

This study aimed to enhance the weak antibacterial activity of silk fibroin (SF) by creating a composite edible coating film. The film was composed of chitosan (CS), SF, and a 3% (v/v) cinnamon essential oil microemulsion (CEOM), which showed excellent inhibition rates of over 99% against two bacteria and four fungi. The resulting film had a transparency of 84.6% and a contact angle of 61.85° on hydrophobic surfaces. In addition, it exhibited a low water vapor permeability of 1.09 × 10−12 g·cm−1·s−1·Pa−1. These properties make it ideal for use in food coating applications. To assess the preservation capabilities of the composite films, strawberries were coated with different films: CS, SF, SF-CEOM, and SF-CS-CEOM. The results showed that the SF-CS-CEOM film had a similar effect to the SF-CEOM film in suppressing the deterioration of strawberries, when compared to the untreated group, and the shelf life of the strawberries was extended from 2 days to 8 days. The SF-CS-CEOM film inhibits oxidation and metabolism by reducing gas exchange, thereby protecting the integrity of cell membranes, maintaining firmness, and reducing weight loss, while delaying the onset of spoilage by inhibiting microbial growth.