Development and characterization of bioactive chitosan/mung bean starch composite films incorporated with tarragon polyphenols for blueberry preservation

Growing environmental awareness has driven a heightened focus on natural bioactive food packaging materials. In this study, a chitosan/mung bean starch (CS/MBS) composite film incorporated with tarragon polyphenols (TGP) was developed, and the effects of TGP concentration on the film's structural and functional properties were systematically investigated. The films were further evaluated for their ability to preserve the postharvest quality of blueberries. The results showed that the incorporation of TGP increased film thickness (0.082–0.089 mm), opacity (1.32–1.88 mm −1 ) and swelling degree (377.02–414.28 %) while significantly enhancing barrier and mechanical performance. At 5 % TGP content, the film exhibited the highest oxygen permeability, water resistance, and tensile strength, with oxygen permeability (0.54 × 10 −3  g mm·m −2 ·d −1 ·kPa −1 ) decreased by 86.5 % and tensile strength (1.69 × 10 3  Pa) increased by 33.63 % relative to the control. Furthermore, the incorporation of TGP markedly enhanced the films' antioxidant and antibacterial properties. Structural and thermal analyses confirmed that hydrogen bonding between TGP and the polysaccharide promoted uniform dispersion and increased structural compactness. On day 8, the blueberry preservation experiments demonstrated that CS/MBS-TGP films effectively inhibited microbial growth (3.4–4.01 log CFU/g) and decay, reduced weight loss by 18.8–24.9 %, and alleviated softening. Additionally, the films maintained titratable acidity (0.61–0.69 %) and total soluble solids (13.68–13.76 %), while enhancing the antioxidant defense capacity of blueberries by 1.88–4.12 times. Overall, the CS/MBS-TGP composite film, derived from renewable tarragon waste and natural polysaccharides, exhibited excellent bioactivity and represents an economical and sustainable strategy for extending the shelf life of perishable foods.