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. 2025 Jun 6;14(12):2015.
doi: 10.3390/foods14122015.

Preservation of Anthocyanins in Postharvest Grapes Through Carboxymethyl Chitosan Films Containing Citrus Essential Oil Emulsion via Enzymatic Regulation

Xinye Wu  1 , Haiying Wang  1 , Yuan Zhou  1 , Wei Xi  1 , Yiqin Zhang  1 , Shanshan Li  1 , Jiaying Tang  1 , Suqing Li  1 , Qing Zhang  1 , Yaowen Liu  1 , Jingming Li  2 , Mingrui Chen  1 , Wen Qin  1
Affiliations

Preservation of Anthocyanins in Postharvest Grapes Through Carboxymethyl Chitosan Films Containing Citrus Essential Oil Emulsion via Enzymatic Regulation

Xinye Wu et al. Foods. .

Abstract

Carboxymethyl chitosan (CMCS) exhibits excellent film-forming capability but suffers from limited water resistance. To enhance hydrophobicity and antimicrobial properties, citrus essential oil was emulsified directly with citrus pectin and dispersed into the CMCS matrix. This study investigated the effects of varying emulsion concentrations (0, 1, 3, 5, and 7 wt%) on film performance. FT-IR, XRD, and SEM analyses confirmed uniform emulsion distribution within the CMCS matrix with favorable compatibility. Increased emulsion loading improved water resistance, antioxidant activity, and antimicrobial efficacy of the CMCS-based films, with the 3% emulsion concentration achieving optimal mechanical strength (TS: 4.09 MPa, EAB: 144.47%) and water vapor permeability (1.30 × 10-10 g·m·(Pa·s·m2)-1). Applied to grape preservation, the films significantly delayed quality deterioration of grapes. Furthermore, by modulating the activity of enzymes involved in anthocyanin metabolism, the films could effectively extend the shelf life of grapes by suppressing the oxidative degradation of anthocyanins.

Keywords: anthocyanin; carboxymethyl chitosan; emulsion; enzyme activity; grape.

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Conflict of interest statement

The authors declare no conflicts of interest.

Figures

Figure 1
Figure 1
Appearance (A) and transmittance (B) of CMCS films containing 0%, 1.0% and 3.0%, 5.0%, 7.0% of citrus essential oil emulsion.
Figure 2
Figure 2
XRD (A), FT-IR (B), DSC (C), surface morphology (D1–D5, 500×) and cross-section morphology (E1–E5, 3.00k×) of CMCS films containing 0%, 1.0% and 3.0%, 5.0%, 7.0% of citrus essential oil emulsion.
Figure 3
Figure 3
Stress–strain curves (A), tensile strength (B), elongation at break (C), young’s modulus (D), toughness (E) and thickness (F) of CMCS films containing 0%, 1.0% and 3.0%, 5.0%, 7.0% of citrus essential oil emulsion. Different minuscule letters indicate significant differences between groups (p < 0.05).
Figure 4
Figure 4
DSC of CMCS films containing 0%, 1.0% and 3.0%, 5.0%, 7.0% of citrus essential oil emulsion.
Figure 5
Figure 5
WVA (A), WVP (B), DPPH radical scavenging activity (C), zone of inhibition of CMCS films containing 0%, 1.0% and 3.0%, 5.0%, 7.0% of citrus essential oil emulsion (D,E). The red circle indicates the dissolved films. Different letters indicate significant differences (p < 0.05).
Figure 6
Figure 6
Appearance (A) and color difference (L (B), a (C), b (D)) of grapes treated with CMCS films containing 0%, 1.0% and 3.0%, 5.0%, 7.0% of citrus essential oil emulsion during storage.
Figure 7
Figure 7
Changes in weight loss rate (A), hardness (B), TA (C), TSS (D), TPC (E), and TAC (F) of grapes treated with CMCS films containing 0%, 1.0% and 3.0%, 5.0%, 7.0% of citrus essential oil emulsion during storage.
Figure 8
Figure 8
Changes in enzyme activity associated with anthocyanin metabolism (PAL activity (A), CHI activity (B), F3H activity (C), UFGT activity (D), β-GC activity (E)) of grapes treated with CMCS films containing 0%, 1.0% and 3.0%, 5.0%, 7.0% of citrus essential oil emulsion during storage.
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