Fabrication and Characterization of Eco-Friendly Polyelectrolyte Bilayer Films Based on Chitosan and Different Types of Edible Citrus Pectin

Abstract

The eco-friendly polyelectrolyte bilayer films were prepared by layer-by-layer (LBL) casting method using chitosan (CS) and four types of edible citrus pectin as film substrates. The results showed that the polyelectrolyte bilayer films exhibited excellent comprehensive properties. Furthermore, the interaction between CS and pectin was closely related to the degree of methyl-esterification (DM), molecular weight (Mw), and zeta potential of pectin. The low DM, Mw, and high zeta potential of the low methyl-esterified pectin (LM) resulted in a denser internal structure of the bilayer film, stronger UV shielding performance, and stronger gas barrier ability. The high DM and Mw of the high methyl-esterified pectin (HM) endow the bilayer film with stronger mechanical properties, thermal stability, and antifogging property. The microstructural and spectroscopic analysis showed that there are hydrogen bonds and electrostatic interactions between the layers. Overall, the developed CS-pectin polyelectrolyte bilayer films provided potential applications for food bioactive packaging.

Tailoring Pectin-PLA Bilayer Film for Optimal Properties as a Food Pouch Material

“…This property contributes to the increased moisture content in bilayer films with pectin and PLA, exceeding films made solely of pectin or PLA. The fact that pectin is water-attracting enhances the moisture absorption of the bilayer film, leading to its higher moisture content [ 59 ]. Therefore, combining pectin and PLA in a bilayer film results in a higher moisture content due to pectin’s water-attracting quality and PLA’s ability to absorb moisture.…”

“…Low WVP values signify effective protection against water transmission, safeguarding foods from external environmental moisture [ 60 ]. The optimized bilayer film achieved the lowest WVP at 0.002 × 10 −7 g/msPa, showing a substantial 412 to 3800-fold reduction compared to individual pectin and PLA films within the range of 0.825−7.612 × 10 −7 g/msPa ( Table 4 ), probably attributed to the extended diffusion path created by the bilayer structure and the tight intermolecular interactions within the film [ 59 ]. The study highlighted the synergistic effect of combining pectin and PLA, emphasizing their pivotal role in enhancing the water vapor barrier properties of the films.…”

“…The optimized pectin/PLA bilayer film exhibited lower oxygen permeability (OP) compared to individual films, aligning with previous studies. The bilayer chitosan/pectin film (0.70–0.75 g/ms) exhibited lower OP compared to chitosan single film (1.39 g/ms) and various types of single pectin films (0.95–1.14 g/ms), attributed to the polar interaction during polyelectrolyte assembly, forming a dense two-layer film matrix with effective intermolecular bonding [ 59 , 66 ]. This helps to fill the voids between the film matrix and creates a more tortuous transport path that hinders oxygen flow [ 66 ].…”

Characterization of Hydroxyapatite/Chitosan Composite Coating Obtained from Crab Shells on Low-Modulus Ti–25Nb–8Sn Alloy through Hydrothermal Treatment

“…In this study, CS becomes a cationic polyelectrolyte after dissolving CS in CH 3 COOH (HAc) through the following equation [36,37]:…”

Recent Developments in Edible Films and Coatings for Fruits and Vegetables

“…Bilayer films can be developed using two main methods [70,71]: (1) two-steps method, or the continuous application over another matrix, and (2) single-step method, or the homogeneous dispersal of distinct emulsions or colloidal systems. However, bilayer films from the two-steps method are described as the best performing because the films from the dispersion method tend to shrink.…”