Preparation and characterization of nanocomposites based on polylactic acid and silica nanoparticles for food packaging application

Poli(mlečna kiselina) (PLA) predstavlja jedan od najpopularnijih komercijalnih biorazgradivih polimera. Iako može da zameni neke od najčešće korišćenih sintetskih polimera, neka njegova svojstva (loša barijerna, termička i mehanička) još uvek predstavljaju prepreku u široj primeni, posebno za pakovanje hrane. Jedan od najsavremenijih načina prevazilaženja nedostataka u svojstvima biopolimera predstavljaju nanotehnologije. U ovom radu ispitan je uticaj dodatka različitih koncentracija hidrofobnih nanočestica silicijum (IV) oksida (od 0.2 mas.% do 5 mas.%) pripremom uzoraka u rastvoru, i rastopu na toplotna, mehanička, i barijerna svojstva PLA. Morfološke karakteristike uzoraka nanokompozita snimljene su pomoću skenirajuće elektronske mikroskopije (SEM). Ostvarena je izuzetno dobra disperzija i distribucija hidrofobnih čestica silicijum (IV) oksida koje su u malim udelima dodavane u poli(mlečnu kiselinu). Dobra disperzija i distribucija hidrofobnih čestica silicijum (IV) oksida ostvarena je kako pripremom nanokompozita metodom u rastvoru, tako i metodom u rastopu. Toplotna svojstva PLA i pripremljenih nanokompozita proučavana su primenom diferencijalnog skenirajućeg kalorimetra (DSC), dok je stepen kristalnosti određen rasipanjem X zraka pod širokim uglom(WAXD). Mehanička svojstva su ispitivana da bi se odredio uticaj dodatka nanočestica SiO2 na prekidnu čvrstoću i izduženje čistog PLA. Iako su prilikom pripreme materijala metodom u rastvoru, poboljšanja mehaničkih i barijernih svojstava postignuta pri udelima silicijum (IV) oksida u rasponu od 0,2 do 5 mas.%, najznačajnija poboljšanja postignuta su za najmanje udele nanočestica (0,2 mas.% i 0,5 mas.%). Poboljšanja mehaničkih i barijernih svojstava nanokompozita, primenjenih metodom u rastopu, su registrovana i za udele silicijum (IV) oksida od 0,2 do 3 mas.%. Takođe je ispitana mogućnost primene pripremljenog nanokompozita na osnovu poli(mlečne kiseline) i silicijum (IV) oksida za pakovanje prehrambenih proizvoda na primeru pakovanja svežeg svinjskog mesa (M. longissimus thoracis et lumborum). Ispitivanjem uticaja materijala za pakovanje svežeg mesa u vakuumu, na parametre tehnološkog (pH, boja), senzorskog, i mikrobiološkog kvaliteta mesa, utvrđeno je da su PLA kao i nanokompoziti na osnovu PLA sa različitim udelima silicijum (IV) oksida, pogodni za vakuum pakovanje i skladištenje svežeg svinjskog mesa.Poly(lactic acid) presents one of the most popular bio-polymers for diverse applications. However, the use of PLA as food packaging material is limited due to poor barrier and mechanical properties. These properties could be improved by incorporation of nanoparticles into polymer matrix. In this work neat PLA films and PLA films with different percentage of hydrophobic fumed silica nanoparticles (0,2 wt.% to 5 wt.%) were prepared by solution casting and melt blending methods. Several procedures were used to characterize the influence of different silica content on dispersion (SEM), crystalline behavior (WAXD), thermal stability (DSC, TGA), mechanical and barrier properties. It is shown that the applied techniques and selection of specific hydrophobic spherical nanofiller provide a good dispersion and distribution of silica nanoparticles in poly(lactic acid) for both film preparation methods. Characteristics of films prepared by solution casting method showed improvements in mechanical and barrier properties for all loadings of nanofiller but the most significant improvements were achieved for lowest silica content (0,2 wt.% and 0,5 wt.%) The improvements in material characteristics (mechanical and barrier) for melt blending method were also achieved (for concentrations from 0,2 wt.% to 3 wt.%). After film preparation, selected cuts of M. longissimus thoracis et lumborum were packed in prepred films of polymer nanocomposites, and the shelf-life characterisation was conducted on technological, sensory and microbiological paramethers of quality. After shelf-life characterisation it can be concluded that polymer nanocomposites based on PLA and silica nanoparticles could be used for packaging od fresh pork meat in vacuum

Hydrophobic silica nanoparticles as reinforcing filler for poly (lactic acid) polymer matrix

Properties of poly (lactic acid) (PLA) and its nanocomposites, with silica nanoparticles (SiO2), as filler were investigated. Neat PLA films and PLA films with different percentage of hydrophobic fumed silica nanoparticles (0.2, 0.5, 1, 2, 3 and 5 wt. %) were prepared by solution casting method. Several tools were used to characterize the influence of different silica content on crystalline behavior, and thermal, mechanical and barrier properties of PLA/SiO2 nanocomposites. Results from scanning electron microscope (SEM) showed that the nanocomposite preparation and selection of specific hydrophobic spherical nano filler provide a good dispersion of the silica nanoparticles in the PLA matrix. Addition of silica nanoparticles improved mechanical properties, the most significant improvement being observed for lowest silica content (0.2wt.%). Barrier properties were improved for all measured gases at all loadings of silica nanoparticles. The degree of crystallinity for PLA slightly increased by adding 0.2 and 0.5 wt. % of nano filler

PLA films loaded with Achillea millefolium: In vitro antibacterial effects

Antimicrobial packaging as active food packaging represents a suitable packaging form for food in products in particular for foods where microbial contamination occurs primarily at the surface. Poly (lactic acid) (PLA) is one of the most frequently used bio-polymers because of its similarities to conventional polymeric materials used in food packaging, however its use is still limited to short-term packaging applications. This research has been focused on preparation of PLA packaging films modified with bioactive compounds from Achillea millefolium (AM) plant extract as possible active packaging solution. Addition of specific natural compounds could give improvements in mechanical, thermal or barrier properties, as well as the antimicrobial effect with significant impact on prolonging the food shelf-life and its quality and safety. Accordingly, the aim of this study was to determine chemical and antimicrobial properties of crude AM ethanolic extract and PLA composite films loaded with two concentrations of AM extract expressed in weight percent (2 wt. % and 5 wt. %). The AM ethanolic extract showed very good antimicrobial activity against E. coli and S. aureus, while PLA films loaded with 5% AM extract showed significant reduction of initial S. aureus after 24 h contact time compared to neat PLA films (up to 90%). PLA films with 2% and 5% AM content did not show any antimicrobial activity against E. coli. Furthermore, the chemical composition of the ethanolic extract was determined considering its phenolic composition. These results indicated promising potential of incorporation of A. millefolium extract in PLA as an antimicrobial agent for food packaging applications

Impact of processing parameters on tensile strength, inprocess crystallinity and mesostructure in FDM-fabricated PLA specimens

Purpose – This study aims to investigate the impact of layer thickness, extrusion temperature, extrusion speed and build plate temperature on the tensile strength, crystallinity achieved during fabrication (herein, in-process crystallinity) and mesostructure of Poly(lactic acid) specimens. Both tensile strength and in-process crystallinity were optimized and verified as the function of processing parameters, and their relationship was thoroughly examined. Design/methodology/approach – The four key technological parameters were systematically varied as factors on three levels, using the statistically designed experiment. Surface response methodology was used to optimize tensile strength and crystallinity for the given ranges of input factors. Optimized factor settings were used in a set of confirmation runs, where the result of optimization was experimentally confirmed. Material characterization was performed using differential scanning calorimetry and X-ray diffraction analysis, while the effect of processing parameters on mesostructure was examined by scanning electron microscopy. Findings – Layer thickness and its quadratic effect are dominant contributors to tensile strength. Significant interaction between layer thickness and extrusion speed implies that these parameters should always be varied simultaneously within designed experiment to obtain adequate process model. As regards, the in-process crystallinity, extrusion speed is part of two significant interactions with plate temperature and layer thickness, respectively. Quality of mesostructure is vital contributor to tensile strength during FDM process, while the in-process crystallinity exhibited no impact, remaining below the 20 per cent margin regardless of process parameter settings. Originality/value – According to available literature, there have been no previously published investigations which studied the effect of process parameters on tensile strength, mesostructure and in-process crystallinity through systematic variation of four critical processing parameters

Recyclable mono materials for packaging of fresh chicken fillets: New design for recycling in circular economy

The focus on sustainability and circular economy is leading to a need for development of new food packaging concepts, including recyclable materials that ideally consist of a single material in a monolayer system. This research was focused on the possibility of replacing complex multilayered material [amorphous polyethylene terephthalate/ polyethylene (APET/PE)] with simple recyclable mono material [highdensity polyethylene (HDPE)] for packaging of chicken fillets in modified atmosphere packaging (CO2/N2: 60%/40%). Bacterial growth measured as total viable count (TVC), lactic acid bacteria and Enterobacteriaceae, Brochothrix thermosphacta and Escherichia coli for chicken fillets packed in HDPE mono materials was compared with chicken fillets packed in APET/PE. TVC increased during the storage period (24 days) with high level of TVC count (7 log10 CFU/g) recorded at Days 19–20 of storage in both HDPE and APET/PE material. No significant differences were recorded in off-odour between chicken stored in APET/PE compared with HDPE in CO2/N2 atmosphere during the storage period (samples were regarded as acceptable on the 24th day of storage). The drip loss increased in all samples during storage, and no significant differences between samples stored in different materials were recorded. Significant differences in bacterial growth were recorded between samples with different gas volume to product volume (G/P) ratio (Day 17), implying that higher G/P ratio is resulting in lower TVC count. The lowest G/P ratio caused the highest drip loss, whereas addition of CO2 emitter reduced the drip loss to some extent. This research is very encouraging as it provides new insight into the use of monolayer materials as well as the importance of design for recycling in circular economy.publishedVersio

Recyclable mono materials for packaging of fresh chicken fillets: New design for recycling in circular economy

The focus on sustainability and circular economy is leading to a need for development of new food packaging concepts, including recyclable materials that ideally consist of a single material in a monolayer system. This research was focused on the possibility of replacing complex multilayered material [amorphous polyethylene terephthalate/ polyethylene (APET/PE)] with simple recyclable mono material [highdensity polyethylene (HDPE)] for packaging of chicken fillets in modified atmosphere packaging (CO2/N2: 60%/40%). Bacterial growth measured as total viable count (TVC), lactic acid bacteria and Enterobacteriaceae, Brochothrix thermosphacta and Escherichia coli for chicken fillets packed in HDPE mono materials was compared with chicken fillets packed in APET/PE. TVC increased during the storage period (24 days) with high level of TVC count (7 log10 CFU/g) recorded at Days 19–20 of storage in both HDPE and APET/PE material. No significant differences were recorded in off-odour between chicken stored in APET/PE compared with HDPE in CO2/N2 atmosphere during the storage period (samples were regarded as acceptable on the 24th day of storage). The drip loss increased in all samples during storage, and no significant differences between samples stored in different materials were recorded. Significant differences in bacterial growth were recorded between samples with different gas volume to product volume (G/P) ratio (Day 17), implying that higher G/P ratio is resulting in lower TVC count. The lowest G/P ratio caused the highest drip loss, whereas addition of CO2 emitter reduced the drip loss to some extent. This research is very encouraging as it provides new insight into the use of monolayer materials as well as the importance of design for recycling in circular economy

Enhancement of Gas Barrier Properties and Durability of Poly(butylene succinate-co-butylene adipate)-Based Nanocomposites for Food Packaging Applications

International audiencePoly(butylene succinate-co-butylene adipate) (PBSA)-based materials are receiving growing attention in the packaging industry for their promising biodegradability. However, poor gas barrier properties and low durability of biodegradable polymers, such as PBSA, have limited their wide-spread use in food packaging applications. Here we report a scalable solution to improve gas barrier properties and stabilize PBSA against photo-aging, with minimal modifications to the biodegradable polymer backbone by using a commercially available and biocompatible layered double hydroxide (LDH) filler. We investigate and compare the mechanical, gas barrier, and photoaging properties of PBSA and PBSA-LDH nanocomposite films produced on a pilot scale. An increase in rigidity in the nanocomposite was observed upon addition of LDH fillers to neat PBSA, which direct the application of neat PBSA and PBSA-LDH nanocomposite to different food packaging applications. The addition of LDH fillers into neat PBSA improves the oxygen and water vapour barriers for the PBSA based nanocomposites, which increases the attractiveness of PBSA material in food packaging applications. Through changes in the viscoelastic behaviour, we observe an improved photo-durability of photoaged PBSA-LDH nanocomposites compared to neat PBSA. It is clear from our studies that the presence of LDH enhances the lifetime durability and modulates the photodegradation rate of the elaborated biocomposites

ANTIMICROBIAL NANOMATERIALS FOR FOOD PACKAGING APPLICATIONS

ABSTRACT: Food packaging industry presents one of the fastest growing industries nowadays. New trends in this industry, which include reducing food as well as packaging waste, improved preservation of food and prolonged shelf-life together with substitution of petrochemical sources with renewable ones are leading to development of this industrial area in diverse directions. This multidisciplinary challenge is set up both in front of food and material scientists. Nanotechnology is recently answering to these challenges, with different solutions-from improvements in materials properties to active packaging solutions, or both at the same time. Incorporation of nanoparticles into polymer matrix and preparation of hybrid materials is one of the methods of modification of polymer properties. Nano scaled materials with antimicrobial properties can act as active components when added into polymer, thereby leading to prolonged protective function of pristine food packaging material. This paper presents a review in the field of antimicrobial nanomaterials for food packaging in turn of technology, application and regulatory issues