Improving the Oxygen Barrier of Polyamide Food Packaging by Using Nanoclay

The effect of nanoclay additive on polyamide film oxygen permeability is investigated from the perspective of possible use as a laminate component for low-cost food packaging material. Montmorillonite nanoclay was melt-mixed in an industrial grade polyamide by twin-screw extrusion and the mixture was hot-pressed to a ~50 µm thick film. The film with 10 wt.% of nanoclay loading showed a 17 % decrease in the oxygen transmission rate (OTR), as compared to the pristine polyamide film (72 and 87 cm3/m2∙24 h, respectively). Despite the relatively high loading of the filler the obtained OTR exceeds that of the food packaging preferred upper limit of 10 cm3/m2∙24 h. XRD measurements confirmed the near-complete exfoliation of the nanoclay platelets. The platelets were found to be at an average angle of 9.5 degrees relative to the film’s surface plane. To comply with the requirements for food packaging, this angle needs to be decreased down to 0.4 degrees. To achieve this, different film-making methods enabling better control over the filler particles’ orientation need to be explored. Nanoclay addition increased the films’ yield strength (23 % for 10 wt.% film) and stiffness, while not affecting the films’ optical appearance.

The Effect of Chitosan Type on Biological and Physicochemical Properties of Films with Propolis Extract

The aim of the research was to determine the influence of chitosan type and propolis extract concentration on biological and physicochemical properties of chitosan-propolis films in terms of their applicability in food packaging. The films were prepared using three types of chitosan: from crab shells, medium and high molecular weight and propolis concentration in the range of 0.75–5.0%. The prepared polysaccharide films were tested for antimicrobial properties, oxygen transmission rate (OTR) and water vapor transmission rate (WVTR). Moreover, sorption tests and structural analysis were carried out. Microbiological tests indicated the best antimicrobial activity for the film consisting of high molecular weight chitosan and 5.0% propolis extract. Both the type of chitosan and propolis concentration affected transmission parameters—OTR and WVTR. The best barrier properties were recorded for the film composed of high molecular weight chitosan and 5.0% propolis extract. The results of sorption experiments showed a slight influence of chitosan type and a significant effect of propolis extract concentration on equilibrium moisture content of tested films. Moreover, propolis extract concentration affected monolayer water capacity (Mm) estimated using the Guggenheim, Anderson and de Boer (GAB) sorption model. The obtained results indicate that chitosan films with an addition of propolis extract are promising materials for food packaging applications, including food containing probiotic microorganisms.

Assessing The Suitability of New Film Laminates For Sustainable Insect Eradication By Modified Atmosphere In Museums

The increasing demand for applying modified inert atmosphere (MIA) systems for insect eradication in museums has led to the desire for lower-cost consumable materials, particularly laminated plastic films. An ultra-low oxygen-permeable laminate is required for creating successful MIA systems to keep the oxygen concentration lower than 0.3%, which is commercially available but at a high cost. The wide use of local laminated films for food preservation makes them a perfect target for testing and improvement for MIA applications. However, the lack of laboratory oxygen permeability test methods to gauge the potential of local laminates for inclusion in MIA applications distracts attention from looking at them as alternatives and encourages the expense on extremely expensive imported ones. Therefore, the present work investigates the potential of employing two laminates (one local and one imported) to create a successful leak-proof MIA system. A laboratory easy-to-use test method was developed to assess the oxygen-gas retention property of each laminate by measuring its oxygen permeability and consequently oxygen transmission rate (OTR). The test method is a sealed static diffusion chamber separated in the middle by a known area (cm2) of the test laminate to be tested. The test relies on measuring the concentration of oxygen in either sides of the laminate membrane within the sealed system and monitors the change over time to assess the OTR of the laminate. The specifications and design of the test chamber are adapted from the ASTM Designation: E2945 − 14, to meet the facilities of a typical artefact fumigation laboratory. The test is undertaken at standard MIA conditions (temperature of 25°C, relative humidity of 45%, and target oxygen concentration of 0.3). Results indicated that the new method is useful for an unlimited number of tests of an unlimited number of laminates. The conducted tests proved that the local laminate normally used for food packaging has superior advantages over the long-used imported ones.

Design and Development of Enhanced Antimicrobial Breathable Biodegradable Polymeric Films for Food Packaging Applications

The principle of breathable food packaging is to provide the optimal number of pores to transfer a sufficient amount of fresh air into the packaging headspace. In this work, antimicrobial microporous eco-friendly polymeric membranes were developed for food packaging. Polylactic acid (PLA) and polycaprolactone (PCL) were chosen as the main packaging polymers for their biodegradability. To develop the microporous films, sodium chloride (NaCl) and polyethylene oxide (PEO) were used as porogenic agents and the membranes were prepared using solvent-casting techniques. The results showed that films with of 50% NaCl and 10% PEO by mass achieved the highest air permeability and oxygen transmission rate (O2TR) with PLA. Meanwhile, blends of 20% PLA and 80% PCL by mass showed the highest air permeability and O2TR at 100% NaCl composition. The microporous membranes were also coated with cinnamaldehyde, a natural antimicrobial ingredient, to avoid the transportation of pathogens through the membranes into the packaged foods. In vitro analysis showed that the biodegradable membranes were not only environmentally friendly but also allowed for maximum food protection through the transportation of sterile fresh air, making them ideal for food packaging applications.

Seed Health of Chickpea as Influenced by Different Packaging during Storage

A storage experiment was conducted to know the influence of cloth, gunny, high density polythene (HDPE), and vacuum packed bags on the seed health of chickpea for 18 months. To investigate, chickpea seeds were packed in all the bags and were kept in ambient conditions. During the storage period, there was a lot of fluctuation in moisture content of the seeds based on the relative humidity in cloth, gunny, and HDPE bags due to the pervious nature of packaging materials whereas, there was no moisture fluctuation in vacuum packed bags due to lower water vapor and oxygen transmission rate and higher thickness of polythene bag used for vacuum package. After 8 months of storage period, there was bruchids infestation to the seeds stored in cloth, gunny, and HDPE bags whereas, no bruchids infestation were seen to vacuum packed bag even after 18 months of storage but germination, root length, shoot length, seedling vigour index, seedling dry weight has reduced and mean germination time, electrical conductivity of seed leachates has increased due to seed aging. Hence, vacuum packaging technology can be effectively used for storage of chickpea seeds for longer period without any aid of chemicals.

Mechanical, Barrier, Adhesion and Antibacterial Properties of Pullulan / Graphene Bio Nanocomposite Coating on Spray Coated Nanocellulose Film for Food Packaging Applications

In this study, an environmentally friendly and biodegradable pullulan/graphene bio nanocomposite was prepared and coated on the nanocellulose film to improve the surface, mechanical, barrier and antibacterial properties. The nanocellulose films were prepared by using a spray coating of nanocellulose suspension on stainless steel plates. The graphene nanoparticles were prepared by the modified Hummers method. The pullulan/graphene bio nanocomposites were prepared by solvent method with the addition of various wt% (0, 0.05, 0.1, 0.2) of graphene with pullulan. The coating was carried out by the roller coating method. Results showed that the increased graphene nanoparticles in pullulan coating increased the opacity, surface hydrophobicity, tensile strength, oxygen transmission rate and watervapour transmission rate of the coated nanocellulose film. Also, the coated film showed excellent antibacterial properties against both gram-negative E.coli and gram-positive S.aureus. In this research work, it was concluded that the graphene nanoparticles of 0.2 wt% showed efficient results. The exceptional properties of the pullulan/graphene bio nanocomposite coating on the nanocellulose film will give a new pathway to high performance food packaging applications.

Cephalopods Inspired Rapid Self-Healing Nanoclay Composite Coatings with Oxygen Barrier and Super-Bubble-Phobic Properties

Polymeric coatings with oxygen barrier properties are an important technology in food packaging that can extend the shelf life of food products and reduce waste. Although a typical technology in practical use is the deposition of metal or inorganic materials between multilayer films to reduce the oxygen transmission rate, once the film is damaged, oxygen permeates through the damaged area, damaging the packaged food. In addition, nanobrick wall structures consisting of nanoplatelet bricks have the potential to replace barrier films made of inorganic materials, however, they similarly lack repair performance or have slow repair speed despite having repair performance. Inspired by the rapid self-repair mechanism of cephalopods, the study develops a nanoclay-containing coating that can rapidly repair surface damage via water. By introducing CaCl₂-derived counterions and montmorillonite for nanobrick wall structures into polyelectrolyte multilayers stacked by layer-by-layer self-assembly, the non-covalent polymer network is increased, resulting in mimicking a strong cephalopod-derived β-sheet structure and non-covalent intermolecular interactions derived from cephalopods. Regardless of the amount of montmorillonite added, the self-healing process was completed within 10 sec. The high-water retention at the surface showed super-bubble-phobicity in water and inhibited gas permeation. The oxygen permeability of the coatings with more than a certain amount of montmorillonite was less than 1/100 of that of bare polyethylene. The ultra-fast self-healing gas barrier coating has the potential to be used not only for food products but also for electronics and pharmaceutical packaging and gas separation applications. The key technology developed in this study provides novel insights into the construction of self-healing membranes made of composite materials and will contribute to the formation of a sustainable society.

Cephalopods Inspired Rapid Self-Healing Nanoclay Composite Coatings with Oxygen Barrier and Super-Bubble-Phobic Properties

Polymeric coatings with oxygen barrier properties are an important technology in food packaging that can extend the shelf life of food products and reduce waste. Although a typical technology in practical use is the deposition of metal or inorganic materials between multilayer films to reduce the oxygen transmission rate, once the film is damaged, oxygen permeates through the damaged area, damaging the packaged food. In addition, nanobrick wall structures consisting of nanoplatelet bricks have the potential to replace barrier films made of inorganic materials, however, they similarly lack repair performance or have slow repair speed despite having repair performance. Inspired by the rapid self-repair mechanism of cephalopods, the study develops a nanoclay-containing coating that can rapidly repair surface damage via water. By introducing CaCl₂-derived counterions and montmorillonite for nanobrick wall structures into polyelectrolyte multilayers stacked by layer-by-layer self-assembly, the non-covalent polymer network is increased, resulting in mimicking a strong cephalopod-derived β-sheet structure and non-covalent intermolecular interactions derived from cephalopods. Regardless of the amount of montmorillonite added, the self-healing process was completed within 10 sec. The high-water retention at the surface showed super-bubble-phobicity in water and inhibited gas permeation. The oxygen permeability of the coatings with more than a certain amount of montmorillonite was less than 1/100 of that of bare polyethylene. The ultra-fast self-healing gas barrier coating has the potential to be used not only for food products but also for electronics and pharmaceutical packaging and gas separation applications. The key technology developed in this study provides novel insights into the construction of self-healing membranes made of composite materials and will contribute to the formation of a sustainable society.

Preparation and Characterization of Polystyrene Hybrid Composites Reinforced with 2D and 3D Inorganic Fillers

Polystyrene (PS)/silicate composites were prepared with the addition of two organoclays (orgMMT and orgZenith) and two mesoporous silicas (SBA-15 and MCF) via (i) solution casting and (ii) melt compounding methods. X-ray diffraction (XRD) analysis evidenced an intercalated structure for PS/organoclay nanocomposites. Thermogravimetric analysis indicated improvement in the thermal stability of PS-nanocomposites compared to the pristine polymer. This enhancement was more prevalent for the nanocomposites prepared with a lab-made organoclay (orgZenith). Tensile measurement results indicated that elastic modulus increment was more prevalent (up to 50%) for microcomposites prepared using mesoporous silicas as filler. Organoclay addition led to a decrease in oxygen transmission rate (OTR) values. This decrement reached up to 50% for high organoclay content films in comparison to pristine PS film. Decrement above 80% was measured for microcomposites with mesoporous silicas and 5 wt% filler content obtained via melt compounding.

Films Based on Mater-Bi® Compatibilized with Pine Resin Derivatives: Optical, Barrier, and Disintegration Properties

Mater-Bi® NF866 (MB) was blended with gum rosin and two pentaerythritol esters of gum rosin (labeled as LF and UT), as additives, to produce biobased and compostable films for food packaging or agricultural mulch films. The films were prepared by blending MB with 5, 10, and 15 wt.% of each additive. The obtained films were characterized by optical, colorimetric, wettability, and oxygen barrier properties. Moreover, the additives and the MB-based films were disintegrated under composting conditions and the effect of each additive on the biodegradation rate was studied. All films were homogeneous and optically transparent. The color of the films tended to yellow tones due to the addition of pine resin derivatives. All the formulated films presented a complete UV-transmittance blocking effect in the UVA and UVB region, and those with 5 wt.% of pine resin derivatives increased the MB hydrophobicity. Low amounts of resins tend to maintain the oxygen transmission rate (OTR) values of the neat MB, due to its good solubilizing and compatibilizing effects. The disintegration under composting conditions test revealed that gum rosin completely disintegrates in about 90 days, while UT degrades 80% and LF degrades 5%, over 180 days of incubation. As expected, the same tendency was obtained for the disintegration of the studied films, although Mater-Bi® reach 28% of disintegrability over the 180 days of the composting test.