Modification of Physio-Mechanical Properties of Chitosan-Based Films via Physical Treatment Approach

The premise of this work is the modification of the properties of chitosan-based film for possible use in food packaging applications. The biofilm was prepared via thermal and mechanical treatment through blending polymers with chitosan using Polyvinyl Alcohol (PVA) and loading different types of chemical agents, i.e., citric acid (CA), succinic acid (SA), and tetraethoxysilane (TEOS). The modification was carried out under high-speed homogenization at elevated temperature to induce physical cross-linkage of chitosan polymer chains without a catalyst. The findings showed that PVA improved the chitosan films' Tensile strength (TS) and elongation at break (Eb). The presence of chemicals caused an increase in the film strength for all samples prepared, in which a 5% w/w of chemical in the optimum composition CS/PVA (75/25) provided the maximum strength, namely, 33.9 MPa, 44.0 MPa, and 41.9 MPa, for CA-5, SA-5, and TEOS-5, respectively. The chemical agents also increased the water contact angles for all tested films, indicating that they promoted hydrophobicity. The chemical structure analysis showed that, by incorporating three types of chemical agents into the CS/PVA blend films, no additional spectral bands were found, indicating that no covalent bonds were formed. The thermal properties showed enhancement in melting peak and degradation temperature of the blend films, compared to those without chemical agents at the optimum composition. The X-ray diffraction patterns exhibited that PVA led to an increasing crystallization tendency in the blend films. The morphological observation proved that no irregularities were detected in CS/PVA blend films, representing high compatibility with both polymers.

Quality Assessment of Waste from Olive Oil Production and Design of Biodegradable Packaging

The use of olive pomace from olive oil production is still insufficient. The lingering olive pomace is harmful to the environment. On the other hand, the world is increasingly polluted with plastic or by-products from the production of biodegradable products. Considering these two problems, the aim of this work was to develop a mixture and create biodegradable disposable tableware characterized by high antioxidant activity. The disposable tableware was made by mixing olive pomace with teff flour or/and sorghum groats and lecithin. Baking was carried out at the temperature of 180 °C. The best variant of the mixture for the preparation of disposable tableware was olive pomace, teff flour, sorghum groats and lecithin. These vessels were the toughest, with low water absorption and had a high antioxidant potential due to the high content of polyphenols and omega acids. Protecting the cups and bowls with beeswax had a positive effect on reducing water absorption.

Impact of γ-irradiation and SBR content in the compatibility of aminated (PVC/LLDPE)/ZnO for improving their AC conductivity and oil removal

In some cases, blends containing PVC and LLDPE show low compatibility. Adding styrene-butadiene rubber to the PVC/LLDPE mixtures leads to a noticeable increase in tensile strength and compatibility of the blends. Also, an improvement in tensile strength is observed after incorporating SBR compatibilizer resulting in entirely different gamma irradiation doses. Without a compatibilizer, the mixture exhibits a distributed PVC and LLDPE phase with variable sizes and shapes; even a sizable portion of the domains resemble droplets. Styrene butadiene rubber (SBR) and gamma radiation make mixtures of (PVC/LLDPE) more compatible. The SEM study of the blends demonstrated that adding the compatibilizer resulted in finer blend morphologies with less roughness. At the same time, gamma irradiation reduced this droplet and gave a more smooth surface. Poly(vinyl chloride) (PVC) was chemically modified with four different amino compounds, including ethylene diamine (EDA), aniline (An), p-anisidine (pA) and dimethyl aniline (DMA) for improving the electric conductivity and oil removal capability of the blend polymer. All ionomers were prepared by nucleophilic substitution in a solvent/non-solvent system under mild conditions. This work novelty shows a sustainable route for producing oil adsorption materials by recycling plastic waste. After the amination process of poly(vinyl chloride) the oil adsorption was significantly enhanced.

Utilization of By-Products from Livestock: Study on the Mechanical and Thermal Properties of Biodegradable Containers Made with Pork Skin Gelatin Polymer

This study aimed to develop a biodegradable container made of pork gelatin. Gelatin was extracted from pork skin by hot water at 80 °C, and containers were prepared by adding eggshell powder (20%) as a pore agent, and walnut powder (0.08 wt%; PEW1, 0.14 wt%; PEW2) to improve hardness. The blends were molded for each experiment and dried at 30 °C for 24 h, at 40 °C for 16 h, and at 121 °C for 16 h. The containers were analyzed with respect to morphological (SEM; scanning electron microscope), mechanical (tensile strain and stress), and thermal (DSA; differential scanning calorimetry and TGA; thermogravimetric analysis) properties, as well as biodegradability. SEM investigation showed a smoother surface for PEW1 than for PEW2. The tensile stress of PEW2 (37.86 MPa) was significantly higher than that of PEW1 (28.40 MPa), and the melting enthalpies were 137.60 J/g (PEW1) and 309.60 J/g (PEW2). TGA showed similar properties, but PEW2 contained more lignin; therefore, its decomposition temperature was higher. The PEW1 and PEW2 containers were completely biodegraded after approximately 7 and 11 weeks, respectively. Walnut shell powder increased the hardness, but slowed the biodegradation process. The applications of this biodegradable container are short-lived products such as food packaging.

The Combined Effect of Hot Water Treatment and Chitosan Coating on Mango (Mangifera indica L. cv. Kent) Fruits to Control Postharvest Deterioration and Increase Fruit Quality

The synergistic effect of dipping in 55 °C for 5 min of hot water (HW) and 1% chitosan coating during the storage of mango at 13 ± 0.5 °C and 85%–90% relative humidity for 28 days was investigated. The combined treatment significantly suppressed the fruit decay percentage compared with both the single treatment and the control. In addition, the specific activities of key plant defense-related enzymes, including peroxidase (POD) and catalase (CAT), markedly increased. The increase occurred in the pulp of the fruits treated with the combined treatment compared to those treated with HW or chitosan alone. While the control fruits showed the lowest values, the combination of pre-storage HW treatment and chitosan coating maintained higher values of flesh hue angle (h°), vitamin C content, membrane stability index (MSI) percentage, as well as lower weight loss compared with the untreated mango fruits. The combined treatment and chitosan treatment alone delayed fruit ripening by keeping fruit firmness, lessening the continuous increase of total soluble solids (TSS), and slowing the decrease in titratable acidity (TA). The results showed that the combined application of HW treatment and chitosan coating can be used as an effective strategy to suppress postharvest decay and improve the quality of mango fruits.

Trends in packaging material for food products: historical background, current scenario, and future prospects

The commercial demand for food products and dietary supplements has increased drastically in the last few decades. The packed food products and nutritional supplements have made a profound impact on the modern human lifestyle. Since ancient times, storage and long-term use of food products remain a significant challenge for humans. There are different parameters for the evaluation of food products and dietary supplements broadly categorized as quality control and quality assurance. On an average million tons of food, materials get spoiled daily worldwide due to lack of storage and transportation point out packaging systems inequalities. To ensure the quality of packed food products and nutritional supplements among available measures, packaging remained an important event and had been refined from time to time to provide a standard. Over a period, the packaging industry has evolved using modern technology from the conventional methods of new generation packaging, including glass, wood, and paper to most new biodegradable materials. The ancient pattern of packaging; manual packaging has been taken over by an automated system of packing, resulting in enhanced output with minimal chance of damage to valuable products for humanity. The article will emphasize new insights into current packaging system not only provide the quality of these products but also in aiming new heights beyond conventional technologies and consumer opinions. In the present study, we have given more emphasis on novel methods of packaging, the packaging materials, quality of packed products, and their impacts of food products on the environment.

Inspired by nature: Microbial production, degradation and valorization of biodegradable bioplastics for life-cycle-engineered products

The global environmental pollution by micro- and macro-plastics reveals the consequences of an extensive use of recalcitrant plastic products together with inappropriate waste management practices that fail to sufficiently recycle the broad types of conventional plastic waste. Biobased and biodegradable plastics are experiencing an uprising as their properties offer alternative waste management solutions for a more circular material economy. However, although the production of such bioplastics has advanced on scale, the end-of-life (EOL) (bio)technologies to promote circularity are lacking behind. While composting and biogas plants are the only managed EOL options today, advanced biotechnological recycling technologies for biodegradable bioplastics are still in an embryonic stage. Thus, developing efficient biotechnologies capable of transforming bioplastic waste into high-value chemical building blocks or into the constituents of the original polymer offers promising routes towards life-cycle-engineered products. This review aims at providing a comprehensive state-of-the-art overview of microbial-based processes involved in the complete lifecycle of bioplastics. The current trends in the bioplastic market, the beginning and EOL scenarios of bioplastics, and a critical discussion on the key factors and mechanisms governing microbial degradation are systematically presented. Also, a critical evaluation of terminology and international standards to quantify polymer biodegradability is provided together with the latest biotechnological recycling strategies, including the use of different pre-treatments for (bio)plastic waste. Finally, the challenges and future perspectives for the development of life-cycle-engineered biobased and biodegradable plastic products are discussed.

Using the method of pyrolytic mass spectrometry in the study of biodegradable polymeric materials

The results of pyrolytic mass spectrometry studies of biodegradable polymeric materials based on polyolefins and segmented polyurethanes with various functional additives are summarized. The structure and composition of initial and after exposure in soil, climate chamber and after exposure to microorganisms (bacteria, yeast) composites are characterized. In the research presented, influence of acetates and complexonates of metals, including cobalt, copper and zinc, on the structural changes in the high pressure polyethylene (HPPE) occurring under the impact of factors such as temperature, humidity and UV-radiation is investigated. It was established, that samples of HPPE, modified by cobalt acetate and cobalt and copper complexonates are responsive and most sensitive to the action of above-mentioned physical factors. Investigation of a segmented polyurethanes (SPU) of a different chemical structure influenced by a factors, modeling of the environmental conditions was conducted. It was shown using pyrolytic mass-spectrometry method and monitoring of samples’ weight loss that under the influence of above-mentioned environmental factors in the SPU occurs processes, resulting to changing its micro heterogeneous structure. It is established that SPU having ester links in its structure and being exposured in soil for 120 days is predominantly attacked by microorganisms, then the main active factor appears to be soil’ pH value – after 300 days in soil with alkaline or acid solution SPU sample decomposes into a separate fragments. Features of the chemical structure of urethane polymers synthesized on the base of hydroxylated rapeseed oil (polyol) were examined. Analysis of the results showed that the macromolecular compounds obtained are segmented polyurethanes which thermal degradation occurs in two stages: hard blocks are destroyed at the first stage, while polyol part (soft blocks) decomposes at the second stage, allowing to identify the temperature area of polymer destruction and thus its temperature region of operation. It is shown that the most suitable from the viewpoint of environmental friendly is polyurethane composition containing more than 50% of polyol. Thermal mass-spectrometry (TMS) has been employed to investigate processes of thermal destruction of segmented polyurethane and it’s compositions filled by polysaccharides: starch, dextrin, chitosan. The features of thermal destruction for segmented polyurethane and related compositions before and after their storage in a soil have been determined. Application TMS is shown to permit the processes of biodegradation of polymeric materials to investigate.

Compostable Polylactide and Cellulose Based Packaging for Fresh-Cut Cherry Tomatoes: Performance Evaluation and Influence of Sterilization Treatment

For food packaging, plastic materials display large appeal, mostly due to their versatility, mechanical, optical and barrier properties. However, they play an important role in environmental concerns and waste management issue. Compostable bioplastics represent alternative materials designed for a lower environmental impact. In this work, a biobased compostable packaging, constituted by polylactide (PLA) trays and NatureFlex™ film, was evaluated for fresh-cut cherry tomato. A comparative analysis was accomplished using traditional packaging materials, that is, polyethylene terephtalate (PET) trays and polypropylene (PP Coex) film. Structural stability under food contact conditions, mechanical and physical-chemical properties were investigated. Tensile mechanical properties, puncture resistance, contact angle (CA) and attenuated total reflection Fourier-transform infrared spectroscopy (ATR-FTIR), before and after UV or radiofrequency (RF) sterilization treatment, were evaluated. UV irradiation method resulted the less invasive one. Therefore, oxygen and water vapor transmission rate (OTR and WVTR), overall chemical migration test, biodegradation assessment by biochemical oxygen demand (BOD) according to ISO 14851 and disintegration test by ISO 20200 were carried out to establish the further influence of UV sterilization on the packaging. Overall, data showed that the biobased compostable packaging for a prolonged shelf-life of fresh-cut cherry tomato has better properties that were surprisingly enhanced by the UV treatment.

Graft modification of carboxymethyl chitosan with styrene and its biological applications

Background

Carboxymethyl chitosan (CMCh) is a water-soluble chitosan derivative and it has been widely used in biomedical applications due to its unique properties. Modification of CMCh by graft copolymerization with different monomers is done in order to enhance its applications.

Results

Graft copolymerization of styrene (S) onto CMCh using ammonium persulfate (APS) as initiator was successfully done with optimization of grafting parameters. The new materials were prepared in nano size. The antibacterial activities against Streptococcus pneumonia (RCMB 010010), Staphylococcus aureus (RCMB 010028) as Gram-positive and Escherichia coli (RCMB 010052) as Gram-negative bacteria and antifungal activity against Aspergillus fumigates (RCMB 02568), Candida albicans (RCMB 05036), Syncephalastrum racemosum (RCMB 05922), and Geotricum candidum (RCMB 05097) were examined using the diffusion agar technique. Also, the cytotoxicity effect against mammalian cell lines (MCF-7cells (human breast cancer) and HTC-116 (colon carcinoma)) was evaluated.

Conclusions

The obtained data proved that grafted carboxymethyl chitosan with styrene (CMCh-g-S) shows better antimicrobial activities, while parent carboxymethyl chitosan showed higher activity than new grafted materials. Also the nano scaled grafted CMCh showed higher activities than grafted carboxymetyl chitosan in macro scale.

Sprayed in-situ synthesis of polyvinyl alcohol/chitosan loaded silver nanocomposite hydrogel for improved antibacterial effects

To overcome the practical limitations of hydrogel preparations, applications and strength-based problems, the present study utilizes the use of sprayers for preparing polyvinyl alcohol/chitosan (PVA/CH) hydrogels. The particle size, morphology, stability, release studies and antibacterial activity of silver nanoparticles (AgNPs) had been studied. The particle size of AgNPs was found to be in the range of 4.59-10 nm (75 °C) with a polydispersity index (PDI) of 0.84. The morphological images exhibited inter-connecting porous structure with pore size in submicron's (<1 µm). Major infra-red spectral peaks of PVA (2946.67 cm^-1; stretching of CH, 1142.72 cm^-1; CO stretching) and CH (3287.49 cm^-1; OH stretching, 2917.48 cm^-1; CH stretching) maintain their place in PVA/CH and PVA/CH/Ag hydrogels. In addition, X-ray diffraction (XRD) pattern showed peaks with 2θ values at 38.08°, 44.29° and 64.50° corresponding to the crystal planes of (1 1 1), (2 0 0) and (2 2 0), respectively, allocated to face-centered cubic crystalline structure of AgNPs. The drug release and antibacterial studies showed a maximum release of 91.83% from hydrogels and a concentration dependent zone of inhibition (ZOI) for >24 h, respectively. Thus, the newly developed sprayed hydrogels could turn out to be a suitable dressing material for wound healing applications.

Biodegradable Composites Developed from PBAT/PLA Binary Blends and Silk Powder: Compatibilization and Performance Evaluation

Silk fibroin powder and biodegradable polybutylene adipate terephthalate (PBAT)/poly lactide (PLA) blends were melt-mixed together to fabricate natural and synthetic polymers as possible new sources of biomaterials. Morphological observations conducted through scanning electron microscopy indicated poor dispersion of the silk powder agglomerates, which resulted from strong hydrogen interactions between silk powder chains in the PBAT/PLA matrix. Although the silk powder agglomerates decreased the mechanical properties, as silk powder fractions increased, the ternary blend with 10 wt % silk powder still displayed high impact strength of 108 J/m and tensile modulus of 1.2 GPa. On the basis of mechanical analysis, this blend offered potential applications in fields which required high impact strength. Blends which contained Joncryl experienced a decrease in storage modulus. Furthermore, rheological studies confirmed that the viscosity of the PBAT/PLA/Silk powder blends decreased, which indicated possible weakening of hydrogen bonds between the silk chains, caused by the reaction between the epoxy groups of Joncryl. This reaction provides a possible method to improve the processability of this natural polymer and to improve its distribution in polymer blends.

How Stress Treatments Influence the Performance of Biodegradable Poly(Butylene Succinate)-Based Copolymers with Thioether Linkages for Food Packaging Applications

Biodegradable poly(butylene succinate) (PBS)-based random copolymers containing thioether linkages (P(BSxTDGSy)) of various compositions have been investigated and characterized from the gas barrier, thermal, and mechanical point of view, after food contact simulants or thermal and photoaging processes. Each stress treatment was performed on thin films and the results obtained have been compared to the same untreated film, used as a standard. Barrier properties with different gases (O₂ and CO₂) were evaluated, showing that the polymer chemical composition strongly influenced the permeability behavior. The relationships between the diffusion coefficients (D) and solubility (S) with polymer composition were also investigated. The results highlighted a correlation between polymer chemical structure and treatment. Gas transmission rate (GTR) mainly depending on the performed treatment, as GTR increased with the increase of TDGS co-unit amount. Thermal and mechanical tests allowed for the recording of variations in the degree of crystallinity and in the tensile properties. An increase in the crystallinity degree was recorded after contact with simulant liquids and aging treatments, together with a molecular weight decrease, a slight enhancement of the elastic modulus and a decrement of the elongation at break, proportional to the TDGS co-unit content.

Applicability of biobased packaging materials for long shelf-life food products

The research aim was to evaluate the applicability of biobased plastics for packing long shelf-life food products, both on laboratory and industrial scale. Therefore, the shelf-life (room temperature) of tortilla chips, dry biscuits and potato flakes packed under air or modified atmosphere (MAP) in xylan and cellulose-based packages was evaluated and compared with their shelf-life in reference (conventional) packaging materials. These tests were followed by packaging trials on industrial lines. Furthermore, overall migration studies and printability tests were performed. Most of the biobased packages showed sufficient barrier towards moisture and gasses to serve as a food packaging material and MAP packaging of long shelf-life food products is possible. But for very moisture-sensitive food products (e.g. dry biscuits), no suited packaging material was found. The quality of the tortilla chips and potato flakes could be guaranteed during their shelf-life, even if packaging materials with lower barrier properties were used. Still, brittleness and seal properties are critical for use on industrial scale (important for use on vertical flow packaging machines). Furthermore, the films were printable and migration tests showed compliance with legislation. This study shows promising results towards the industrial application of biobased packaging materials for long shelflife food products.

Effect of different new packaging materials on biscuit quality during accelerated storage

BACKGROUND

The effect of innovative multilayer packaging materials versus a standard one on biscuit quality was studied during accelerated storage at 25, 35, 45 °C and 50% relative humidity for 92 days. Three different packaging materials were used: metalized orientated polypropylene (OPP)/paper (control); metalized poly-lactic acid (PLA)/paper; metalized OPP with ethylene vinyl acetate pro-oxidant additive (EVA-POA)/paper. EVA-POA additive is used to make the plastic layer biodegradable. Various quality sample parameters (moisture, water activity (aw ), texture, peroxide value (PV), hexanal) were analysed during storage. Rate constants (k) and activation energies (Ea ) of hydration reactions and hexanal formation were calculated.

RESULTS

No remarkable differences in the evolution of primary and secondary lipid oxidation were observed among differently packed biscuits during storage. All samples maintained PV levels between 4 and 14 meq O2 kg(-1) oil. The product in flexible packaging with PLA reached the highest moisture and aw levels, but they did not significantly and adversely affect the other quality characteristics.

CONCLUSION

The obtained results demonstrate that the new tested packaging materials were suitable for commercial biscuit storage, having similar performance and preservation effects on the overall product quality to those of the standard one. Furthermore, these results could make a contribution to the food industry, encouraging the use of packaging materials with a negligible environmental impact as an alternative to petroleum-based ones.

Chitooligosaccharide and its derivatives: preparation and biological applications

Chitin is a natural polysaccharide of major importance. This biopolymer is synthesized by an enormous number of living organisms; considering the amount of chitin produced annually in the world, it is the most abundant polymer after cellulose. The most important derivative of chitin is chitosan, obtained by partial deacetylation of chitin under alkaline conditions or by enzymatic hydrolysis. Chitin and chitosan are known to have important functional activities but poor solubility makes them difficult to use in food and biomedicinal applications. Chitooligosaccharides (COS) are the degraded products of chitosan or chitin prepared by enzymatic or chemical hydrolysis of chitosan. The greater solubility and low viscosity of COS have attracted the interest of many researchers to utilize COS and their derivatives for various biomedical applications. In light of the recent interest in the biomedical applications of chitin, chitosan, and their derivatives, this review focuses on the preparation and biological activities of chitin, chitosan, COS, and their derivatives.