Electrospun fibers as food packaging material

Wrapping of fresh food with electrospun membrane containing nutrient preservation or antimicrobial substances.

The use of electrospun fibers as packaging material is mainly targeted at keeping the freshness of the food for a longer duration. The advantage of electrospinning for such applications lies in the relative ease of encapsulating active agents within the fiber and the process which forms a coating of nonwoven fibrous mat. High surface area of the fibers due to its small diameter also allows quick response to its surrounding conditions with timely release of active agents. Small pore size between the interconnected fibers also acts as a physical barrier against bacteria entry. Chaudhary et al (2014) used an electrospun polyacrylonitrile-silver composite filter media to cover a nutrient media in room condition and passes ambient air through the filter media. When compared to the negative control which is without the protective filter media, the nutrient media protected by the nanofibrous filter remains free of bacteria growth after two months while the unprotected nutrient media show microorganism growth.

Widespread use of food packaging provides an opportunity to reduce environmental impact through the use of abundant and renewable resources. One such material is starch. Zhu et al (2022) was able to electrospin pure starch by dissolving the starch in dimethyl sulfoxide (DMSO) at 70 °C before cooling to room temperature. Electrospinning was carried out at an ambient temperature of 60 °C to facilitate fast vaporization of the solvent to form distinct fibers. Post spinning cross-linking using glutaraldehyde (GTA) vapor was necessary to render the membrane insoluble in water and to increase its tensile strength from ~0.66 MPa to ~9.65 MPa.

Increasing the biodegradation of the food packaging is another way of reducing its environmental impact. Salevic-Jelic et al (2024) electrospun polycaprolactone (PCL) films incorporating sage extract (SE) for use as packaging material. Pseudomonas aeruginosa (PAO1) bacteria was tested for degradation towards PCL due to its esterase-catalyzed enzymatic degradation ability. Bio-disintegration of the PCL film in compost was completed before 90 days which corresponds to the ISO time period requirement for disintegrable material. With the addition of PAO1 into the compost, the disintegration of the PCL film was accelerated demonstrated by the complete disintegration of PCL film without any residues after 3 weeks.

Zein is a natural polymer derived from corn grains. However, its poor mechanical strength meant limited usage in its pure form. Jia et al (2025) used a core-shell fiber structure with a blend of zein and shellac to improve the mechanical properties of the resultant electrospun membrane. Shellac is a natural amphiphilic biopolymer derived from the female lac insect. In the preparation of the core-shell electrospun fibers, the core was a blend of shellac and zein in ethanol aqueous solution and the shell was polyvinylpyrrolidone (PVP) in ethanol aqueous solution. At optimal shellac to zein ratio, the mechanical strength increased from pure zein at 0.57 MPa to 1.15 MPa. The significant increase in mechanical strength was attributed to strong hydrophobic interactions and hydrogen bonding between zein and shellac molecules.

Protection offered by electrospun membrane may be enhanced by the addition of anti-microbial agent into the fibers. To assure food safety, natural occurring anti-microbial agent has been used for loading into electrospun fibers. Plantaricin 423, produced by Lactobacillus plantarum, and bacteriocin ST4SA produced by Enterococcus mundtii has been blended with poly L-lactide and polyethylene oxide mixture and electrospun [Heunis et al 2011]. Despite the use of organic solvent, N, N-dimethyl formamide (DMF) for dissolving the polymers and the peptides and electrospinning at high voltage, the peptides were shown to retain their activity from their inhibition of Enterococcus faecium HKLHS. Dai (2013) demonstrated the release of allyl isothiocyanate vapor from mustard seed meal powder encapsulated in electrospun poly(lactic acid) (PLA)/poly(ethylene oxide) (PEO) fibers. Allyl isothiocyanate vapour is known to exhibit antimicrobial properties and the release of the it can be controlled by varying the ratio of PLA and PEO with maximum release rate recorded when the ratio was one is to one. Gallic acid, a naturally occurring phenolic acid which is known to exhibit anti-inflammatory and antimicrobial, has been encapsulated within electrospun zein fibers. Since zein is a naturally occurring protein, the electrospun packaging is fully made out of natural material. The electrospun mesh has been found to be effective against S. aureus and E. coli although it is only moderately effective against C. albicans with a log reduction of 1 to 2. The electrospun packaging material was found to be stable after 30 days of storage at 60 °C [Neo et al 2014]. Bugatti et al (2018) used electrospun bio-based polyamide 11 (PA11) loaded with halloysite nanotubes (HNTs) filled with lysozyme (50 wt % of lysozyme), a natural antimicrobial molecule, as bio-based pads for extending shelf-life of raw meat. With PA11/5.0 wt % HNTs-lysozyme, the release of lysozyme was more than a month. Anti-bacterial effectiveness of the membrane was tested using Pseudomonas spp., representing microbial dynamics during meat spoilage. Electrospun PA11 membrane without lysozyme was used as control. Over 13 days study period, the bacterial count on the PA11/5 wt % HNTs-lysozyme was one order of magnitude lower than the PA11 therefore demonstrating the potential of the lysozyme loaded membrane against food spoilage. Wei et al (2025) constructed a crosslinked electrospun zein/polyethylene glycol (PEG)/nisin membrane as a packaging material for preservation of cooled goose meat. Both zein and PEG were used as the matrix material with PEG giving strength to the material while nisin is an antibacterial compound. The electrospun membrane was crosslinked using citric acid vapor by placing citric acid solution and the membrane in a chamber heater at 60 °C for 30 min. The crosslinked membrane was found to be effective in inhibiting Staphylococcus aureus and Escherichia coli. Pieces of goose breast meat were placed on UV sterilized crosslinked zein/PEG/nisin membrane and stored at 4 °C. The effectiveness of nisin loaded in the membrane in reducing bacteria growth was demonstrated by a slower rate of pH increase due to build-up of alkaline chemicals from the breakdown of protein by bacteria and the lowest bacteria colony count. A measure of TVB-N, a type of volatile alkaline nitrogen-containing material derived from protein breakdown gave a value of 110.28 mg kg^-1 at day 10 which was within the Chinese National Standard GB 2707-2016 of 150 mg kg^-1 and compared well against the exposed meat control which had a value of 180.48 mg kg^-1 on day 8. The membrane structure also reduced the oxidation of the meat as shown by its low TBARS value, which indicates the degree of oxidation and rancidity of fat in meat, of 0.83 mg kg^-1 while the control exceeded 1.0 mg kg^-1 at the end of 10 days. Yue et al (2018) demonstrated the performance of electrospun carboxymethyl chitosan/polyoxyethylene oxide (CMCS) nanofibers for maintaining freshness of strawberries compared to commercial cling wrap and painted with the electrospinning solution to form a coating. Carboxymethyl chitosan was selected due to its antibacterial property and polyoxyethylene oxide was a binder to facilitate electrospinning. The electrospun composite fibers demonstrated good antibacterial property against Escherichia coli and Staphylococcus aureus. The electrospun CMCS membrane was able to reduce water loss while exhibiting adequate air permeability to maintain fruit freshness. After six days of storage at ambient temperature, only the strawberries covered with electrospun CMCS membrane maintained good outer appearance without any rot. Both unprotected control and strawberries wrapped with commercial cling wrap showed various degrees of rotting. Strawberries with CMCS coating on their surface suffered from browning and severe shrinkage but without any rotting.

The antimicrobial effect of compounds can be complex with some effective against only gram positive or gram negative bacteria. Combinations of antimicrobial compounds may also yield synergistic effects against some bacteria. Pleva et al (2025) loaded zein/polyethylene glycol (PEG) fibers with natural antimicrobial compounds and tested the antimicrobial effect against a selection of bacteria. Among single or combined loading of natural antimicrobial compounds, eugenol, thymol and nisin into the fibers, only the combination of eugenol and nisin were found to be effective against Gram-negative bacteria Escherichia coli, and Gram-positive bacteria Staphylococcus aureus and Listeria ivanovii. Against the formation of biofilms, only the combination of eugenol and thymol was able to prevent biofilm formation by all three bacteria. However, high concentration of eugenol and thymol (above 75%) extracted from the fibers was found to exhibit cell contact cytotoxic effects on NIH/3T3 cells. Other single or combinations of the antimicrobial compounds did not exhibit any cytotoxic effect. As packaging material, the addition of the antimicrobial compounds did not change its biodegradable nature with full degradation of every sample after 29 days.

To enhance the effectiveness of food preservation, it is also beneficial for the packaging material to have multiple properties. In addition to antibacterial, food packaging material with antioxidant properties would also help delay spoilage. Zeinali et al (2021) demonstrated the potential use of jujube extract-loaded electrospun polyvinyl alcohol (PVA/JE) nanofiber for strawberry preservation. Both polyvinyl alcohol and jujube extracts are water soluble hence non-toxic solution can be prepared for electrospinning into a nanofibrous membrane. Jujube extracts were found to contain flavonoids which exhibited antioxidant properties. The same extracts also demonstrated antibacterial properties through their inhibition of Staphylococcus aureus and Pseudomonas aeruginosa. For their tests on maintaining the freshness of the strawberries, the strawberries are placed in polyethylene containers and its lid covered with the membrane. The PVA/JE membrane was shown to reduce the ripening process of the fruits with lower weight loss compared to the controls from day 6 to 12. Total soluble solids, firmness and antioxidant capacity of strawberries stored in the jar with PVA/JE membrane was also better than the control at the end of day 12. Sensory evaluation of the strawberries which includes color, texture, taste, appearance and general acceptance was also better in the PVA/JE membrane covered strawberries and no signs of decay was observed at the end of the 12th day. Ye et al (202) used a dip coating method to load electrospun poly(lactic-co-caprolactone)/gelatin (PLCL/GEL) fibers with Tannic acid (TA). TA is a natural polyphenol with strong antibacterial, antioxidant and anti-inflammatory properties. The PLCL/GEL/TA showed rapid degradation with weight loss of 50% in the first week followed by slow and continuous degradation. Release of TA was rapid in the first 20 min followed by gradual and continuous release over the next two days. This release profile is favorable for initial inhibition of bacteria and subsequent maintenance of bacteria free enclosed environments. The antioxidant property was demonstrated by a scavenging rate of 83.82% for PLCL/GEL/TA(10 wt%) while electrospun PLCL/GEL membrane without TA was only 19.96%. PLCL/GEL/TA demonstrated antibacterial property against E. coli and S. aureus. When tested as a packaging material for blueberries, the electrospun membrane without TA showed signs of decay within the first couple of days. With PLCL/GEL/TA(10 wt%), there was no color or structural deterioration after 5 days of storage except small patches of mold. Note that with 20wt% TA, the preservation performance was lower than with 10wt% TA and this may be attributed to greater hydrophilicity of the former which accumulated more moisture and condensation inside the package thereby accelerating food spoilage.

Spoilage of food is commonly caused by fungi and inhibition of fungi growth is important to maintain the freshness of food. Zhang et al (2022) examined the effectiveness of electrospun polyvinyl alcohol/β-Cyclodextrin (PVA/β-CD, 6:1) with Zanthoxylum bungeanum essential oil (ZBEO, 10%) as packaging material for maintaining freshness of strawberries and cherries. The antifungal activity of PVA/β-CD loaded with ZBEO was tested against Penicillium, Aspergillus flavus or Botrytis cinerea. Inhibition of close to 90% of the fungi exposed to the vapors of ZBEO emitted from the electrospun PVA/β-CD membrane was observed at day 7. The ZBEO loaded PVA/β-CD membrane was also found to be superior in maintaining the freshness of strawberries and cherries compared to untreated fruits, blank film and free ZBEO enclosed in a jar with the fruits. Food spoilage may be due to many contributing factors such as fungal spores, bacterial contamination and oxidation. A packaging material with multifunctional capability is desirable to protect the food. Venezia et al (2024) constructed an electrospun poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) film loaded with humic acid for use as a packaging material. Humic substances (HS) are rich in redox-active compounds, such as quinones, phenols, carboxyl, and hydroxyl moieties with antibacterial and antifungal properties. PHBV and HS were first prepared in 2,2,2-trifluoroethanol (TFE) and water respectively before combining to form an emulsion for electrospinning. With 3% w/w loading of HS, the resultant fibrous membrane showed antioxidant properties with 2,2-diphenyl-1-picrylhydrazyl radical (DPPH) inhibition of about 70% after 24 h which was almost two times as high as neat PHBV. Excellent antibacterial activity was demonstrated by strong inhibition of Escherichia coli (E.C.), Bacillus cereus (B.C.) and Salmonella typhi (S.T.). Inhibition was more evident for gram negative bacterial strains, S.T. and E.C. but slightly reduced against gram positive bacterial strains, Staphyloccocus aureus (S.A), Enterococcus faecalis (E.F.) and Listeria monocitogenes (L.M.). Antifungal activity was also demonstrated on two prevalent fungal pathogens, Candida albicans (C. albicans) and Aspergillus flavus (A. flavus) with performance that was similar or better than the positive control, Amphotericin B. Antibacterial and antifungal properties have been attributed to the phenolic groups in HS which disrupt the cell membranes of fungi and bacteria.

In the development of smart packaging for food preservation during transport, the release or increased release rate of antimicrobial agents can be triggered by specific stimulus. Shi et al (2021) encapsulated salicylaldehyde precursors (SP) and hexanal precursors (HP) into electrospun ethyl acetate (EA)/polyethylene oxide (PEO) fibers. Both hexanal and salicylaldehyde are known to have antimicrobial properties. However, as these aldehydes are volatile and susceptible to oxidative degradation in the environment, they need a polymer carrier for protection until it is released. Shi et al (2021) showed that the release of SP and HP was higher with exposure to higher concentration of citric acid vapor. When used as packaging material, increasing concentration of citric acid vapor within the headspace would induce faster release of SP and HP which would offer protection to the fruits and vegetables. However, more investigations need to be carried out as aldehydes self-react or react with other molecules through acid-catalyzed aldol condensation which would reduce the amount of SP and HP in the head-space. Despite this, the amount of SP and HP concentration is higher than in the absence of citric acid vapor.

Food spoilage generally requires the presence of oxygen and moisture. Packaging with oxygen scavenging ability is able to control headspace oxygen content and improve product quality and shelf-life. Cherpinski et al (2019) constructed an oxygen-scavenging multilayered biopaper containing palladium nanoparticles as a potential oxygen scavenging packaging material. The multilayered biopaper comprised of a cellulose base paper, coated with electrospun poly(3-hydroxybutyrate) (PHB) and polycaprolactone (PCL) polymer-containing palladium nanoparticles (PdNPs). The layer of electrospun PHB function as a water barrier and electrospun PCL is the carrier for oxygen scavenging palladium nanoparticles. Such configuration is necessary as electrospun PHB loaded with PdNPs was found to exhibit poor oxygen scavenging capacity after annealing to improve water barrier performance. PHB is a better water barrier material compared to PCL but electrospun PCL loaded with PdNPs was found to exhibit much better oxygen scavenging ability. To take advantage of the better water barrier performance of electrospun PHB and oxygen scavenging ability of electrospun PdNPs/PCL fibers, both fibers were incorporated onto a cellulose base layer to form a multilayered biopaper. Gouvea et al (2024) adopted a bilayered structure in the development of a functional film packaging. The base layer was made of thermoplastic starch (TPS) prepared by extrusion with the addition of microcrystalline cellulose (MCC) at 2.0 mass% content. The presence of MCC increases the water contact angle of the starch base layer. The second layer was made of electrospun chitosan (CS)/poly(ethylene-co-vinyl alcohol) (EVOH) loaded with Gallic acid (GA). GA is a natural substance with antioxidant, anticancer, anti-inflammatory, and antimicrobial properties. With the presence of GA, the bilayered film showed good antioxidant activity. EVOH is an excellent oxygen barrier polymer and its addition reduces the oxygen permeability of the bilayered film. The combination of the various functional properties of the materials make this a potential antioxidant film for the packaging of food products.

A concern of using electrospun fibers in packaging is whether loose fiber strands may get into the food. This may be mitigated by using proper adhesion methods to fuse the fibers or fuse the fibers to a base substrate. Taking advantage of the good dispersion of Ag nanoparticles in electrospun fibers, Castro-Mayorga et al (2017) coated a commercial polyhydroxyalkanoate (PHA) substrate with electrospun PHA loaded with Ag nanoparticles to introduce antibacterial properties to the material. To fuse the electrospun fibers with the base substrate, hot compression was used. With compression under heat, the electrospun fibers completely fused with the base substrate such that no fibers were observed following the heat treatment. The nanoparticles were being transferred to the combined substrate and its distributions indicates where the fibers once were. The multilayered substrate retains good transparency and are active against Salmonella enterica (gram negative) but did not show any antibacterial effect against Listeria monocytogenes (gram positive). Pardo-Figuerez et al (2018) used a combination of electrospinning and electrospraying to create a superhydrophobic coating on polyethylene terephthalate (PET) film as transparent food packaging. Electrospinning of polylactide (PLA) solution was first out carried to deposit a layer of fibers on the PET film. This increases the hydrophobicity of the film from 82° to 96° using water contact angle test. Unfortunately, annealing of the bilayer film at temperatures ranging from 90°C to 170°C reduces the water contact angle to 73° at 170°C annealing temperature. This may be attributed to the partial loss of fiber structure especially at temperatures above 120°C. To increase hydrophobicity of the film, SiO₂ microparticles were electrosprayed on top of electrospun PLA fibers. An optimum annealing temperature of 160°C was found to create good adhesion between the fibers, SiO₂ microparticles and the film. A water contact angle of 171° and sliding angle of 6° were obtained thus making the film superhydrophobic. The film also exhibited good optical transparency following heat treatment.

Using a base substrate for collection of electrospun fibers to form a bilayered membrane provides the opportunity to incorporate functional agents on both the substrate and the electrospun fibers. Gouvea et al (2024) constructed a bilayered packaging material with thermoplastic cornstarch (TPS), incorporated with microcrystalline cellulose (MCC) and a second layer consisted of gallic acid (GA) encapsulated in 1:1 chitosan/poly(ethylene-co-vinyl alcohol) (CS/EVOH) nanofibers. The addition of MCC to TPS helped to reduce the oxygen permeability (OP) of the packaging material. Adding a layer of electrospun CS/EVOH nanofibers significantly reduced the OP of the packaging material. The addition of GA imparted antioxidant activity to the packaging material. 15% addition of GA to CS/EVOH was able to give the bilayered material a radical scavenging activity against the DPPH radical of 903.8 µmol.L^-1.Eq. Trolox.g^-1.

The release of active agents may also be triggered by environmental stimuli. Liu (2016) used the moisture released by fresh tomatoes to trigger the release of thymol encapsulated within electrospun mats. The polymer used for electrospinning was polyvinyl alcohol which is swells when comes into contact with water or moisture. It is important to note that for encapsulation of volatile compound like thymol, the compound gets vaporized during electrospinning and the remaining concentration needs to be determined post-electrospinning. Liu (2016) was able to demonstrate the increased release of thymol when the mat was placed in higher humidity environment. Their study successfully showed that the shelf life of fresh tomatoes can be extended by at least 5 days.

For roots and tubers, keeping them fresh is about preventing sprouting. Some chemicals such as peppermint essential oil have been shown to be able to prevent or delay sprouting of tubers. Ramachandran et al (2017) encapsulated peppermint essential oil in electrospun polyurethane (PU)/ polymethylmethacrylate (PMMA) fibers to use as anti-sprouting agent in stored potatoes. The test subject with the loaded electrospun fibers showed no sprouting for 30 days while the controlled samples (electrospun mat without peppermint essential oil) sprouted in 10 days. This shows that the loaded peppermint essential oil is effective in delaying sprouting. However, it is important to note that the test was carried out in an airtight container. Dumitriu et al (2017) recommended using electrospinning to create a coating for existing high performance barrier films. The electrospun fibers will be loaded with anti-oxidant compound to prevent oxidative degradation reactions of fats, proteins and pigments which will lead to degradation of the meat. In their experiment, polycaprolactone (PCL) was used as the carrier matrix and vitamin E (α-tocopherol), selected as plant-based phenolic antioxidant. The vitamin E loaded into the electrospun PCL fibers were shown to be accessible and effective as an antioxidant. However, more studies will be required to demonstrate its effectiveness in delaying food product degradation and the increment in shelf-life.

Investigation of electrospun membrane to retain freshness of food products are not restricted to just fruits and vegetables. With the proper selection of additives, fish has also been shown to benefit from a protective layer of electrospun membrane. Li et al (2021) investigated the use of core-shell electrospun fibers with antibacterial methyl ferulate as the active ingredient encapsulated within the core and zein as the shell layer for preserving sea bass. The electrospun core-shell methyl ferulate/zein fiber membrane showed an initial release of 30% of the load in the first 8 h. The release rate slowed to 77.5% of the load at 84 h and stabilized at 83% from 84 to 132 h. Inhibition of bacteria was demonstrated by soaking the membrane in the culture medium of Shigella putrefaciens. Through determining the pH value, lipid oxidation content and total volatile basic nitrogen (TVB-N) content, the electrospun core-shell methyl ferulate/zein fiber membrane was able to keep the sea bass fresher compared to uncovered and zein only fiber membrane covered sea bass.

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