Active food packaging of cellulose acetate: Storage stability, protective effect on oxidation of riboflavin and release in food simulants

Enhancing cellulose acetate biodegradability in cigarette filters: an in-depth analysis of thermal alkaline pretreatment, microbial dynamics, and breakdown pathway prediction

BACKGROUND

The demand for bioplastics has increased exponentially as they have emerged as alternatives to petrochemical plastics. However, there is a substantial lack of knowledge regarding bioplastic degradation. This study developed a novel pretreatment method to improve the accessibility of a bioplastic substrate for biodegradation. In this study, cellulose acetate, a bioplastic found in the world's most littered waste, e.g. cigarette filters, was selected as a potential substrate. Before anaerobic digestion, three thermal alkaline pretreatments: TA 30 °C, TA 90 °C, and TA 121 °C, were used to evaluate their effects on the chemical alterations of cellulose acetate.

RESULT

The ester groups in cellulose acetate were significantly reduced by the TA 30 °C pretreatment, as seen by a decrease in C = O stretching vibrations and shortening of C - O stretches (1,270 ∼ 1,210 cm- 1), indicating effective removal of acetyl groups. This pretreatment significantly enhanced cellulose acetate biodegradability to a maximum of 91%, surpassing the previously reported cellulose acetate degradation. Methane production increased to 695.0 ± 4 mL/g of volatile solid after TA 30 °C pretreatment, indicating enhanced cellulose acetate accessibility to microorganisms, which resulted in superior biogas production compared to the control (306.0 ± 10 mL/g of volatile solid). Diverse microbes in the anaerobic digestion system included hydrolytic (AB240379_g, Acetomicrobium, FN436103_g, etc.), fermentative, and volatile fatty acids degrading bacteria (JF417922_g, AB274492_g, Coprothermobacter, etc.), with Methanobacterium and Methanothermobacter being the sole hydrogenotrophic methanogens in the anaerobic digestion system. Additionally, an attempt to predict the pathway for the effective degradation of cellulose acetate from the microbial community in different pretreatment conditions.

CONCLUSIONS

To the best of our knowledge, this is the first study to estimate the maximum cellulose acetate degradation rate, with a simple and cost-effective pretreatment procedure. This approach holds promise for mitigating the environmental impact of cellulose acetate of cigarette filters and presents a sustainable and economically viable waste management strategy.

Active cellulose acetate/purple sweet potato anthocyanins@cyclodextrin metal-organic framework/eugenol colorimetric film for pork preservation

As a natural pH-sensing colorant, purple sweet potato anthocyanins (PSPAs) have demonstrated great potential in colorimetric film for freshness monitoring. However, the photothermal instability of PSPAs is still a challengeable issue. Herein, γ-cyclodextrin metal-organic framework (CD-MOF) loaded with PSPAs (PSPAs@CD-MOF, i.e., PM) and eugenol (EUG) were incorporated in cellulose acetate (CA) matrix for developing a smart active colorimetric film of CA/PM/EUG, where PM and EUG were hydrogen-bonded with CA. Attentions were focused on the photothermal colorimetric stability, colorimetric response, and antibacterial activity of the films. The presence of PM and EUG endowed the film outstanding UV-blocking performance and enhanced the barrier against water vapor and oxygen. Target film of CA/PM15/EUG10 had good photothermal colorimetric stability due to the protection of CD-MOF on PSPAs and the color changes with pH-stimuli were sensitive and reversible. In addition to antioxidant activity, CA/PM15/EUG10 had antibacterial activity against Escherichia coli and Staphylococcus aureus. The application trial results indicated that the CA/PM15/EUG10 was valid to indicate pork freshness and extended the shelf-life by 100 % at 25 °C, which has demonstrated a good perspective on smart active packaging for freshness monitoring and shelf-life extension.

Characterization and modeling of diffusion kinetics of rosemary oleoresin extract from gellan gum-based film

Fresh food products are highly prone to oxidation and microbial attack, rendering them unsuitable for consumption. Thus, active food packaging was developed to protect and prolong food shelf-life. Zein/gellan gum (GG) based active film is developed by incorporating rosemary oleoresin extract (ROE) (0-20%). The films were characterized by their barrier and antioxidant properties. The release behavior of ROE in fatty and hydrophilic food stimulants was investigated via mathematical modeling. The active films incorporated with 20% ROE have significantly higher oxygen barrier and oxygen transfer is reduced by 20% compared to the control. A tortuous path is created with ROE, which impedes oxygen movement across the film. ROE addition improved water resistance performance by reducing the active film swelling ratio by 31%. This improvement is attributed to the hydrophobic nature of ROE. FTIR shows that the interaction between ROE and the active film is primarily hydrogen bonding and electrostatic interactions. Active film exhibits excellent antioxidant activity, with high TPC, DPPH scavenging activity, and FRAP. Mathematical modeling revealed a higher diffusivity (D) of ROE in fatty food stimulants at 24 °C, attributed to high polarity and solubility in fatty food stimulants. Overall, this active film has an excellent antioxidant effect and could potentially be used as food packaging for high-fat food products to prevent oxidation.

Graphical abstract

Degradation Characteristics of Cellulose Acetate in Different Aqueous Conditions

Cellulose acetate (CA) is widely used in cigarette filters and packaging films, but due to its acetylation, it is difficult to degrade in the natural environment, and the problem of pollution has become a serious challenge. Understanding the degradation behavior and performance of CA in different environments is the basis and prerequisite for achieving its comprehensive utilization and developing efficient degradation methods. In this study, we investigated the degradation performance of CA in different aqueous environments to evaluate the effects of pH, salinity and microorganisms on CA degradation. The CA tows and films were immersed in HCl, NaOH solution, river water, seawater or homemade seawater for 16 weeks and the degradation mechanism was investigated by the changes in weight loss rate, degree of substitution, hydrophilicity, molecular structure and surface morphology. The results showed that the degradation of CA tow and film were the fastest in NaOH solution; the weight loss rates after 16 weeks were 40.29% and 39.63%, respectively, followed by HCl solution, and the degradation performance of CA tow was better than that of film. After 16 weeks of degradation in river water, seawater and homemade seawater, all the weight loss rates were less than 3%. In summary, this study illustrated that the environmental acidity, basicity and high concentration of inorganic salts had a critical promotion effect on the non-enzymatic hydrolysis of CA, whereas the number and type of microorganisms were the key factors affecting the biodegradation of CA.

Recent Advances in Functional Cellulose-based Films with Antimicrobial and Antioxidant Properties for Food Packaging

The packaging of food plays a crucial role in food preservation worldwide. However, traditional packaging systems are passive layers with weak efficiency in protecting the food quality. Therefore, packaged foods are gradually spoiled due to the oxidation and growth of microorganisms. Additionally, most of the commercial packaging films are made of petroleum-based materials which raise environmental concerns. Accordingly, the development of eco-friendly natural-derived active packaging systems has increased the attention of scientists. Cellulose as the most abundant polysaccharide on earth with high biocompatibility, no toxicity, and high biodegradability has extensively been applied for the fabrication of packaging films. However, neat cellulose-based films lack antioxidant and antimicrobial activities. Therefore, neat cellulose-based films are passive films with weak food preservation performance. Active films have been developed by incorporating antioxidants and antimicrobial agents into the films. In this review, we have explored the latest research on the fabrication of antimicrobial/antioxidant cellulose-based active packaging films by incorporating natural extracts, natural polyphenols, nanoparticles, and microparticles into the cellulose-based film formulations. We categorized these types of packaging films into two main groups: (i) blend films which are obtained by mixing solutions of cellulose with other soluble antimicrobial/antioxidant agents such as natural extracts and polyphenols; and (ii) composite films which are fabricated by dispersing antimicrobial/antioxidant nano- or microfillers into the cellulose solution. The effect of these additives on the antioxidant and antimicrobial properties of the films has been explained. Additionally, the changes in the other properties of the films such as hydrophilicity, water evaporation rate, and mechanical properties have also been briefly addressed.

Recent Advances in the Carotenoids Added to Food Packaging Films: A Review

Food spoilage is one of the key concerns in the food industry. One approach is the improvement of the shelf life of the food by introducing active packaging, and another is intelligent packaging. Detecting packed food spoilage in real-time is key to stopping outbreaks caused by food-borne diseases. Using active materials in packaging can improve shelf life, while the nonharmful color indicator can be useful to trace the quality of the food through simple color detection. Recently, bio-derived active and intelligent packaging has gained a lot of interest from researchers and consumers. For this, the biopolymers and the bioactive natural ingredient are used as indicators to fabricate active packaging material and color-changing sensors that can improve the shelf life and detect the freshness of food in real-time, respectively. Among natural bioactive components, carotenoids are known for their good antimicrobial, antioxidant, and pH-responsive color-indicating properties. Carotenoids are rich in fruits and vegetables and fat-soluble pigments. Including carotenoids in the packaging system improves the film's physical and functional performance. The recent progress on carotenoid pigment-based packaging (active and intelligent) is discussed in this review. The sources and biological activity of the carotenoids are briefly discussed, and then the fabrication and application of carotenoid-activated packaging film are reviewed. The carotenoids-based packaging film can enhance packaged food's shelf life and indicate the freshness of meat and vegetables in real-time. Therefore, incorporating carotenoid-based pigment into the polymer matrix could be promising for developing novel packaging materials.

Synergic versus Antagonist Effects of Rutin on Gallic Acid or Coumarin Incorporated into Chitosan Active Films: Impacts on Their Release Kinetics and Antioxidant Activity

This work deals with the study of the release and antioxidant activity kinetics of three natural antioxidants associated as binary mixture (coumarin, and/or gallic acid and rutin) from chitosan films. Antioxidants were incorporated into film alone or in binary mixture. The aim was to determine the influence of rutin on the phenolic acid and benzopyrone. The UV-visible light transmission spectra of the films were also investigated. Neat chitosan films and chitosan incorporated coumarin exhibited high transmittance in the UV-visible light range, while GA-added chitosan films showed excellent UV light barrier properties. The molecular interactions between chitosan network and antioxidants were confirmed by FTIR where spectra displayed a shift of the amide-III peak. Rutin has a complex structure that can undergo ionization. The chitosan network structure induced change was found to influence the release behavior. The film containing rutin showed the highest antioxidant activity (65.58 ± 0.26%), followed by gallic acid (44.82 ± 3.73%), while coumarin displayed the lowest activity (27.27 ± 4.04%). The kinetic rate against DPPH-free radical of rutin is three times higher than coumarin. The kinetic rates were influenced by the structure and interactions of the antioxidants with chitosan. Rutin exhibited a slow release due to its molecular interactions with chitosan, while coumarin and gallic acid showed faster release. The diffusion coefficient of coumarin is 900 times higher than that of rutin. The rutin presence significantly delayed the release of the gallic acid and coumarin, suggesting an antagonistic effect. However, their presence weakly affects the release behavior of rutin.

Microbiological, thermal and mechanical performance of cellulose acetate films with geranyl acetate

The present work concerns to investigate the microbiological, thermal and mechanical behavior of cellulose acetate films obtained with addition of 0.5 % (v/v) and 1.0 % (v/v) of geranyl acetate by the casting technique. The antimicrobial activities of the polymeric films were assessed against Staphylococcus aureus and Escherichia coli bacteria and against Aspergillus flavus fungal. The achieved results show that the films presented antibacterial and antifungal activities. Moreover, the incorporation of the geranyl acetate in the polymeric films was confirmed by FTIR and TGA technique, while DSC analysis pointed out the compatibility between the geranyl acetate and cellulose acetate. The addition of the geranyl acetate did not modify the mechanical behavior of the cellulose acetate films concerning stiffness and tensile strength. These results suggest that this new material is promising for future applications in biomedical devices and food packaging.

Bionanocomposite Active Packaging Material Based on Soy Protein Isolate/Persian Gum/Silver Nanoparticles; Fabrication and Characteristics

In this study, nanocomposite active films were fabricated containing silver nanoparticles (SNPs) embedded within soy protein isolate (SPI)/Persian gum (PG) matrices. The physical, mechanical, and antibacterial properties of these composite films were then characterized. In addition, scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and X-ray diffraction (XRD) were used to provide information about the microstructure, interactions, and crystallinity of the films. Pure SPI films had poor physicochemical attributes but the addition of PG (0.25, 0.5, or 1 wt%) improved their water vapor permeability, mechanical properties, and water solubility (WS). The moisture content (MC) of the films decreased after the introduction of PG, which was attributed to fewer free hydroxyl groups to bind to the water molecules. Our results suggest there was a strong interaction between the SPI and the PG and SNPs in the films, suggesting these additives behaved like active fillers. Optimum film properties were obtained at 0.25% PG in the SPI films. The addition of PG (0.25%) and SNPs (1%) led to a considerable increase in tensile strength (TS) and a decrease in elongation at break (EB). Furthermore, the incorporation of the SNPs into the SPI/PG composite films increased their antibacterial activity against pathogenic bacteria (Escherichia coli and Staphylococcus aureus), with the effects being more prominent for S. aureus. Spectroscopy analyses provided insights into the nature of the molecular interactions between the different components in the films. Overall, the biodegradable active films developed in this study may be suitable for utilization as eco-friendly packaging materials in the food industry.

Controlled Thermal Release of L-Menthol with Cellulose-Acetate-Fiber-Shelled Metal-Organic Framework

Fragrances have been widely used in many customer products to improve the sensory quality and cover flavor defects. The key to the successful application of fragrance is to realize controlled fragrance release, which relies on the use of an appropriate carrier for fragrance. An ideal fragrance carrier helps to achieve the stable storage and controlled release of fragrance. In this work, a novel composite fragrance carrier with MIL-101 (Cr) as the fragrance host and cellulose acetate fiber (CAF) as the protective shell was developed. The encapsulation effect of MIL-101 (Cr) and the protective function of the CAF shell significantly improved the storage stability of L-menthol (LM). Only 5 wt % of LM was lost after 40 days of storage at room temperature. Encapsulated LM could also be effectively released upon heating due to the thermal responsiveness of CAF. In addition, the composite carrier was highly stable with neglectable Cr leaching under different conditions. The results of this work showed that the developed composite carrier could be a promising carrier for the thermally triggered release of fragrance.

Fabrication of alkali lignin-based emulsion electrospun nanofibers for the nanoencapsulation of beta-carotene and the enhanced antioxidant property

For the greater utilization of β-carotene in antioxidant material, β-carotene-loaded emulsion stabilized by alkali lignin (AL) was successfully electrospinning with poly (vinyl alcohol) (PVA) (PVA/AL/β-carotene nanofiber). Transmission electron microscopy demonstrated the core-shell structure of nanofiber with the average diameter being 356.31 nm, and 85.7 % of β-carotene was effectively encapsulated into the core section. Fourier transform infrared spectra and differential scanning calorimetry revealed the good compatibility and decreased crystallinity of β-carotene, favoring its stability and solubility, respectively. As expected, the PVA/AL/β-carotene nanofiber exhibited higher antioxidant activity than free β-carotene due to the protection of AL matrix and the special structure of nanofiber, as the DPPH free radical scavenging rate being 90.7 % at 7th day. The sustained release behavior of β-carotene and AL from fiber followed Fickian diffusion model, contributing to the greater protection for fish oil than that of emulsion. Thus, this study provides an approach to develop hydrophobic compounds-loaded emulsion electrospun antioxidant material with controlled release property and enhanced activity.

Recent advances in biobased and biodegradable polymer nanocomposites, nanoparticles, and natural antioxidants for antibacterial and antioxidant food packaging applications

Inorganic nanoparticles (NPs) and natural antioxidant compounds are an emerging trend in the food industry. Incorporating these substances in biobased and biodegradable matrices as polysaccharides (e.g., starch, cellulose, and chitosan) and proteins has highlighted the potential in active food packaging applications due to more significant antimicrobial, antioxidant, UV blocking, oxygen scavenging, water vapor permeability effects, and low environmental impact. In recent years, the migration of metal NPs and metal oxides in food contact packaging and their toxicological potential have raised concerns about the safety of the nanomaterials. In this review, we provide a comprehensive overview of the main biobased and biodegradable polymer nanocomposites, inorganic NPs, natural antioxidants, and their potential use in active food packaging. The intrinsic properties of NPs and natural antioxidant actives in packaging materials are evaluated to extend shelf-life, safety, and food quality. Toxicological and safety aspects of inorganic NPs are highlighted to understand the current controversy on applying some nanomaterials in food packaging. The synergism of inorganic NPs and plant-derived natural antioxidant actives (e.g., vitamins, polyphenols, and carotenoids) and essential oils (EOs) potentiated the antibacterial and antioxidant properties of biodegradable nanocomposite films. Biodegradable packaging films based on green NPs-this is biosynthesized from plant extracts-showed suitable mechanical and barrier properties and had a lower environmental impact and offered efficient food protection. Furthermore, AgNPs and TiO₂ NPs released metal ions from packaging into contents insufficiently to cause harm to human cells, which could be helpful to understanding critical gaps and provide progress in the packaging field.

The influence of bio-plastics for food packaging on combined anaerobic digestion and composting treatment of organic municipal waste

The use of bio-plastic-based packaging as an alternative to conventional plastic packaging is increasing. Among the plethora of different bio-based plastics, the most relevant ones are those that, at the end of their life, can be treated with the organic fraction of municipal solid waste. Even in these cases, their impact on the waste processing and recycling is not always positive. This study aim to assess on a laboratory scale the influence on combined anaerobic digestion and composting industrial processes of a bio-based plastic film, namely cellulose acetate (CA), in pure and modified (additions of additive) forms. CA films were mixed with organic waste and subjected to: (i) anaerobic digestion; (ii) active composting and (iii) two stages of curing composting. Anaerobic digestion and composting were monitored through methane yield and oxygen uptake respectively; additionally, the bio-plastics degree of disintegration was assessed during all the processes. The final disintegration of pure and modified CA was 73.82% and 54.66%, respectively. Anaerobic digestion contributes to the disintegration of the material, while aerobic treatment appears to be nearly ineffective, especially for modified CA. The presence of cellulose acetate during anaerobic digestion of food waste increased the methane yield by about 4.5%. Bioassay confirmed the absence of possible toxic effects on the final compost from the bio-plastic treatment. Although bio-based materials are not the only solution to plastic pollution, the findings confirm the need to upgrade the organic waste treatment plants and the necessity to revise the requirements for the use of compost in agriculture.

Recent Advances in Chemically Modified Cellulose and Its Derivatives for Food Packaging Applications: A Review

The application of cellulose in the food packaging field has gained increasing attention in recent years, driven by the desire for sustainable products. Cellulose can replace petroleum-based plastics because it can be converted to biodegradable and nontoxic polymers from sustainable natural resources. These products have increasingly been used as coatings, self-standing films, and paperboards in food packaging, owing to their promising mechanical and barrier properties. However, their utilization is limited because of the high hydrophilicity of cellulose. With the presence of a large quantity of functionalities within pristine cellulose and its derivatives, these building blocks provide a unique platform for chemical modification via covalent functionalization to introduce stable and permanent functionalities to cellulose. A primary aim of chemical attachment is to reduce the probability of component leaching in wet and softened conditions and to improve the aqueous, oil, water vapor, and oxygen barriers, thereby extending its specific use in the food packaging field. However, chemical modification may affect the desirable mechanical, thermal stabilities and biodegradability exhibited by pristine cellulose. This review exhaustively reports the research progress on cellulose chemical modification techniques and prospective applications of chemically modified cellulose for use in food packaging, including active packaging.

Advancements in Biodegradable Active Films for Food Packaging: Effects of Nano/Microcapsule Incorporation

Food packaging plays a fundamental role in the modern food industry as a main process to preserve the quality of food products from manufacture to consumption. New food packaging technologies are being developed that are formulated with natural compounds by substituting synthetic/chemical antimicrobial and antioxidant agents to fulfill consumers’ expectations for healthy food. The strategy of incorporating natural antimicrobial compounds into food packaging structures is a recent and promising technology to reach this goal. Concepts such as “biodegradable packaging”, “active packaging”, and “bioactive packaging” currently guide the research and development of food packaging. However, the use of natural compounds faces some challenges, including weak stability and sensitivity to processing and storage conditions. The nano/microencapsulation of these bioactive compounds enhances their stability and controls their release. In addition, biodegradable packaging materials are gaining great attention in the face of ever-growing environmental concerns about plastic pollution. They are a sustainable, environmentally friendly, and cost-effective alternative to conventional plastic packaging materials. Ultimately, a combined formulation of nano/microencapsulated antimicrobial and antioxidant natural molecules, incorporated into a biodegradable food packaging system, offers many benefits by preventing food spoilage, extending the shelf life of food, reducing plastic and food waste, and preserving the freshness and quality of food. The main objective of this review is to illustrate the latest advances in the principal biodegradable materials used in the development of active antimicrobial and antioxidant packaging systems, as well as the most common nano/microencapsulated active natural agents incorporated into these food-packaging materials.

Designing active mats based on cellulose acetate/polycaprolactone core/shell structures with different release kinetics

Core/shell electrospun mats based on cellulose acetate (CA) and polycaprolactone (PCL) were developed as novel active materials for releasing quercetin (Quer) and curcumin (Cur). The effect of polymeric uniaxial and coaxial electrospun systems and the chemical structures of Quer and Cur on the structural, thermal, and mass transfer properties of the developed mats were investigated. Release modelling indicated that the diffusion of the active agents from the uniaxial PCL fibers was highly dependent on the type of food simulant. Higher diffusion coefficients were obtained for both active agents in acid food simulant due to the higher swelling of the electrospun mats. In addition, CA/PCL coaxial structures slowed down the diffusion of both active agents into both food simulants. CA increased the retention of the active compounds in the polymer structure, resulting in partition coefficients values higher than the values obtained for uniaxial active PCL mats.