Structural Characteristics and Antibacterial Assessment of Chitosan–Frankincense Oil Coatings on Strawberries

This study evaluated the effects of chitosan composite edible coatings with frankincense essential oil on microbial growth and strawberry quality. Four coatings were prepared using 1% and 3% chitosan aqueous solutions, with or without 1% (v/v) frankincense essential oil derived from Boswellia sacra. Fresh strawberries were coated with chitosan and chitosan–frankincense solutions and stored under controlled conditions for eight days. The physical properties of strawberries, such as color, texture, moisture content, pH, and total soluble solids, were evaluated throughout the storage period. Results indicated that neither chitosan nor chitosan–frankincense oil coatings significantly altered the physical properties of the strawberries, such as the color, pH, moisture content, total soluble solids, and hardness at each time point. However, a significant effect of time (2-way ANOVA, p < 0.05) was observed on pH, TSS, color and hardness characteristics of strawberries. All tested coatings effectively inhibited bacterial growth. The strawberries covered with 3% chitosan–frankincense oil coating had the lowest bacterial count (74 CFU/mL). The addition of frankincense to 1% of chitosan significantly reduced the number of bacteria by 1.6-fold. Additionally, chitosan–frankincense oil films significantly reduced the growth of E. coli compared to both the chitosan film and the control. These findings suggest that chitosan combined with frankincense oil can serve as an effective natural alternative for edible coating in food preservation, offering both antimicrobial benefits and quality retention during storage.