The effect of phenolics from bergamot juice powder extracted with different solvents on the physicochemical and antibacterial properties of chitosan films

Abstract

Due to its bitterness, bergamot juice has no practical use, but it is a rich source of phenolic compounds, which provide significant antibacterial and antioxidant activity. In this study, extracts were prepared from spray-dried bergamot juice powder using acetone, dimethylsulfoxide, ethanol, and distilled water. These extracts were then incorporated into chitosan film matrices at 1%, 2%, and 3% (v/v) ratios. The analysis revealed that adding extracts generally created a barrier against light in the chitosan films, improved color, increased moisture content and water solubility, and caused significant enhancements in antioxidant activity, total phenolic content, thickness, mechanical strength, and provided substantial antibacterial activity against both Gram(+) and Gram(-) bacteria. The most effective modification of film properties was achieved by adding 3% acetone extract, while the 1% distilled water extract resulted in the least improvement. Specifically, the transparency, opacity, chroma, moisture, solubility, antioxidant activity, total phenolic content, thickness, puncture strength, and elasticity of pure chitosan film were 4.3–73.8%, 1.13 abs/mm, 15.61, 25.35%, 41.28%, 20.66%, 919.53 ppm, 1.09 N/mm2, 132.44%, and 0.07 mm, respectively. Meanwhile, those of the film with 3% acetone extract were 0.2–70.10%, 2.07 abs/mm, 36.34, 42.33%, 54.64%, 46.13%, 2915.72 ppm, 3.34 N/mm2, 142.68%, and 0.15 mm, respectively. The pure chitosan film exhibited no antibacterial effect against Gram(+) and Gram(-) bacteria, but adding extract enhanced antibacterial activity. Moreover, SEM analysis revealed distinct structural differences in the films, including varying porosity and phenolic distribution. At the same time, FTIR spectra demonstrated shifts in chemical composition and bonding within the films.