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. 2024 Jun 3;25(11):6154.
doi: 10.3390/ijms25116154.

Chitosan/Polyvinyl Alcohol-Based Biofilms Using Ternary Deep Eutectic Solvents towards Innovative Color-Stabilizing Systems for Anthocyanins

Hiléia K S de Souza  1   2 , Marta Guimarães  1 , Nuno Mateus  1 , Victor de Freitas  1 , Luís Cruz  1
Affiliations

Chitosan/Polyvinyl Alcohol-Based Biofilms Using Ternary Deep Eutectic Solvents towards Innovative Color-Stabilizing Systems for Anthocyanins

Hiléia K S de Souza et al. Int J Mol Sci. .

Abstract

Anthocyanins are amazing plant-derived colorants with highly valuable properties; however, their chemical and color instability issues limit their wide application in different food industry-related products such as active and intelligent packaging. In a previous study, it was demonstrated that anthocyanins could be stabilized into green plasticizers namely deep eutectic solvents (DESs). In this work, the fabrication of edible films by integrating anthocyanins along with DESs into biocompatible chitosan (CHT)-based formulations enriched with polyvinyl alcohol (PVA) and PVA nanoparticles was investigated. CHT/PVA-DES films' physical properties were characterized by scanning electron microscopy, water vapor permeability, swelling index, moisture sorption isotherm, and thermogravimetry analysis. Innovative red-to-blue formulation films were achieved for CHT/PVA nanoparticles (for 5 min of sonication) at a molar ratio 1:1, and with 10% of ternary DES (TDES)-containing malvidin-3-glucoside (0.1%) where the physical properties of films were enhanced. After immersion in solutions at different pH values, films submitted to pHs 5-8 were revealed to be more color stable and resistant with time than at acidic pH values.

Keywords: anthocyanins; biopolymers; color stability; scanning electron microscopy; ternary deep eutectic solvents; water vapor permeability.

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Conflict of interest statement

The authors declare no competing financial interests.

Figures

Figure 1
Figure 1
Z-average and PdI values of the PVA nanoparticles as a function of sonication time and cryo-SEM images (2000×) for the non-sonicated PVA (0 min) and sonicated PVA (5 min). a,b,c,A,B data with the same letters are statistically similar at a 95% confidence level.
Figure 2
Figure 2
Variation in the density and viscosity of the PVA solutions with the sonication time.
Figure 3
Figure 3
Cryo-SEM images of CHT/PVA5-NP 1:1 mixtures (2000×) in the presence and absence of TDES (10, 20%) and anthocyanin content.
Figure 4
Figure 4
SI of the films obtained after H2O immersion as a function of time: (A) 0 min of sonication, PVA-NS; (B) 3 min of sonication, PVA3-NPs; (C) 5 min of sonication, PVA5-NPs; (D) 7 min of sonication PVA7-NPs. Molar ratios for the CHT/PVA-NS or CHT/PVAn-NPs mixtures were 3/7, 1/1, and 7/3.
Figure 4
Figure 4
SI of the films obtained after H2O immersion as a function of time: (A) 0 min of sonication, PVA-NS; (B) 3 min of sonication, PVA3-NPs; (C) 5 min of sonication, PVA5-NPs; (D) 7 min of sonication PVA7-NPs. Molar ratios for the CHT/PVA-NS or CHT/PVAn-NPs mixtures were 3/7, 1/1, and 7/3.
Figure 5
Figure 5
SI of the CHT/PVA5-NP 1:1 films containing different percentages of TDES plasticizer with and without mv3glc obtained after H2O immersion as a function of time.
Figure 6
Figure 6
SI of anthocyanin-containing films obtained after 3 h of immersion in water solutions at different pH values.
Figure 7
Figure 7
(a) WVP results for the films obtained with CHT/PVA-NS at different ratios and at different sonication times (CHT/PVAn-NPs) compared with the controls, non-sonicated PVA (PVA-NS 0 min), and CHT; (b) the effect of the different TDES percentages on the WVP results of the films; (c) the effect of the different anthocyanin structures in the WVP results and cryo-SEM images (500×) for the films fabricated with mv3glc (low WVP values). a–d data with the same letters are statistically similar at a 95% confidence level.
Figure 8
Figure 8
Equilibrium moisture sorption isotherms and respective fittings using the GAB model using: (A) non-sonicated PVA, PVA-NS; (B) 3 min of sonication, PVA3-NPs; (C) 5 min of sonication, PVA5-NPs; (D) 7 min of sonication, PVA7-NPs. Molar ratios for the CHT/PVA-NS or CHT/PVAn-NPs mixtures were 3/7, 1/1, and 7/3.
Figure 8
Figure 8
Equilibrium moisture sorption isotherms and respective fittings using the GAB model using: (A) non-sonicated PVA, PVA-NS; (B) 3 min of sonication, PVA3-NPs; (C) 5 min of sonication, PVA5-NPs; (D) 7 min of sonication, PVA7-NPs. Molar ratios for the CHT/PVA-NS or CHT/PVAn-NPs mixtures were 3/7, 1/1, and 7/3.
Figure 9
Figure 9
Equilibrium moisture sorption isotherm of the CHT/PVA5-NP 1:1 films formulated with 10 to 30% of the TDES plasticizer (w/w). The symbols are experimental data, and the lines are from the equations obtained by fitting the experimental data to the GAB equation.
Figure 10
Figure 10
Experimental sorption data and respective fit using the GAB model for the CHT/PVA5-NP 1:1 film formulated with mv3glc (10% TDES) submitted at different pH conditions.
Figure 11
Figure 11
TG curves and DTG (inset graphic) curves for the thermal decomposition of anthocyanins (powder), and the films of CHT, PVA5-NPs, CHT/PVA5-NPs, and CHT/PVA5-NPs containing cy3glc and mv3glc.
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