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The use of biopolymeric materials is restricted for some applications due to their deficient properties in comparison to synthetic polymers. Blending different biopolymers is an alternative approach to overcome these limitations. In this study, we developed new biopolymeric blend materials based on the entire biomasses of water kefir grains and yeast. Film-forming dispersions with varying ratios of water kefir to yeast (100/0, 75/25, 50/50 25/75 and 0/100) underwent ultrasonic homogenisation and thermal treatment, resulting in homogeneous dispersions with pseudoplastic behaviour and interaction between both biomasses. Films obtained by casting had a continuous microstructure without cracks or phase separation. Infrared spectroscopy revealed the interaction between the blend components, leading to a homogeneous matrix. As the water kefir content in the film increased, transparency, thermal stability, glass transition temperature and elongation at break also increased. The thermogravimetric analyses and the mechanical tests showed that the combination of water kefir and yeast biomasses resulted in stronger interpolymeric interactions compared to single biomass films. The ratio of the components did not drastically alter hydration and water transport. Our results revealed that blending water kefir grains and yeast biomasses enhanced thermal and mechanical properties. These studies provided evidence that the developed materials are suitable candidates for food packaging applications.

In the last decades, cellulose nanoparticles have been widely used to reinforce polymeric materials due to their strength and their wide availability in nature. Cellulose nanoparticles are entirely compatible to reinforce natural polymers, as performed in this study. The effect of rice husk cellulose nanofibers (RHCNF) and bacterial nanocellulose (BNC) on water vapor transfer and mechanical properties was studied in yeast biomass films, made from dispersions at pH 6 and 11. Water vapor permeability was reduced at 5 wt% in both reinforcements in films prepared at pH 11, although their influence was negligible at pH 6. Despite both cellulose nanofibres have similar aspect ratios, Young’s modulus, tensile strength, elongation and tensile toughness of films reinforced with BNC were significantly increased with respect to RHCNF films, and both were better than the pure matrix. In this way, the present study provides an interesting contribution regarding the effect of the mentioned nanocellulosic reinforcements on yeast biomass films used for packaging purposes.

International audience; The main objective of this work is the development of new active films based on yeast cell wall obtained by high-pressure homogenization (YCW-H) supplemented with naphtho-γ-pyrone (CL-NGP) extract, which is a bioactive compound produced by Aspergillus tubingensis G131 with great antioxidant potential. A complete characterization of the functional properties of the bioactive films, such as their structural, colour, thermal, mechanical, hydration and water vapour transport, was carried out to evaluate the influence of the addition of the antioxidant compounds. Likewise, the antioxidant capacity of the developed materials and the specific migration of NGPs in food simulants were evaluated. The results showed that CL-NGP extract possessed an important antioxidant activity, which was maintained after incorporation in YCW-H films. The addition of 2 and 5% CL-NGPs decreased the hydration of films and consequently improved the water vapour barrier properties. It was observed that CL-NGPs migrate in fatty food simulants and retain their antioxidant capacity in the simulant. The results obtained in this work showed that bioactive films based on yeast cell walls with the addition of CL-NGPs have the potential to be used as packaging material in systems of interest in the food industry.

In this study, yerba mate waste (YMW) was used to produce a kombucha beverage, and the obtained microbial cellulose produced as a byproduct (KMW) was used to reinforce a mechanically recycled poly(lactic acid) (r-PLA) matrix. Microbial cellulosic particles were also produced in pristine yerba mate for comparison (KMN). To simulate the revalorization of the industrial PLA products rejected during the production line, PLA was subjected to three extrusion cycles, and the resultant pellets (r3-PLA) were then plasticized with 15 wt.% of acetyl tributyl citrate ester (ATBC) to obtain optically transparent and flexible films by the solvent casting method. The plasticized r3-PLA-ATBC matrix was then loaded with KMW and KMN in 1 and 3 wt.%. The use of plasticizer allowed a good dispersion of microbial cellulose particles into the r3-PLA matrix, allowing us to obtain flexible and transparent films which showed good structural and mechanical performance. Additionally, the obtained films showed antioxidant properties, as was proven by release analyses conducted in direct contact with a fatty food simulant. The results suggest the potential interest of these recycled and biobased materials, which are obtained from the revalorization of food waste, for their industrial application in food packaging and agricultural films.

BACKGROUND Yeast biomass, mainly composed of proteins and polysaccharides (mannans and β-glucans), has been proposed to develop films. pH can affect the solubility of polysaccharides, the structure of the cell wall, and the interactions between proteins. Considering the potential impact of these effects, the pH of yeast film-forming dispersions was studied from 4 to 11. RESULTS In tensile tests, samples increased their elongation by increasing pH, from 7 ± 2% (pH 4) to 29 ± 5% (pH 11), but Young's modulus was not significantly modified. Regarding thermal degradation, the maximum degradation rate temperature was shifted 46 °C from pH 4 to 11. Differences in water vapour permeability, colour, opacity, and roughness of films were also found. According to the results of differential protein solubility assay, hydrophobic interactions and hydrogen bonding were promoted at pH 4, but disulfide bonds were benefited at pH 11, in addition to partial β-glucan dissolution and break-up of the alkali-sensitive linkage in molecules from the cell wall. CONCLUSION The results lead to the conclusion that film-functional characteristics were greatly benefited at pH 11 in comparison with the regular pH of dispersion (pH 6). These results could help in understanding and selecting the pH conditions to enhance the desired properties of yeast biomass films. © 2021 Society of Chemical Industry.

Poly(itaconic acid) (PIA) was synthesized via conventional radical polymerization. Then, functionalization of PIA was carried out by an esterification reaction with the heterocyclic groups of 1,3-thiazole and posterior quaternization by N-alkylation reaction with iodomethane. The modifications were confirmed by Fourier transform infrared (FTIR) and proton nuclear magnetic resonance (1H-NMR), as well as ζ-potential measurements. Their antimicrobial activity was tested against different Gram-negative and Gram-positive bacteria. After characterization, the resulting polymers were incorporated into gelatin with oxidized starch and glycerol as film adjuvants, and dopamine as crosslinking agent, to develop antimicrobial-active films. The addition of quaternized polymers not only improved the mechanical properties of gelatin formulations, but also decreased the solution absorption capacity during the swelling process. However, the incorporation of synthesized polymers increased the deformation at break values and the water vapor permeability of films. The antioxidant capacity of films was confirmed by radical scavenging ability and, additionally, those films exhibited antimicrobial activity. Therefore, these films can be considered as good candidates for active packaging, ensuring a constant concentration of the active compound on the surface of the food, increasing products’ shelf-life and reducing the environmental impact generated by plastics of petrochemical origin., This work has been possible thanks to the support of the Agencia Nacional de Promoción Científica y Tecnológica (Argentina) through PICT-2015-3150, the Universidad Nacional de Quilmes (UNQ, Argentina) through R&D program PUNQ 990/19 and MINECO (MAT2016-78437-R; AEI, Spain and FEDER, EU).

International audience; Bioactive packaging is gaining interest in food preservation as an alternative to the incorporation of additives to food formulations. Yeast cell wall is a good candidate for the formation of biodegradable films. In this context, enzymatically hydrolysed yeast cell wall (YCW-E) and fungal extracts, containing naphtho-gamma-pyrones (NGPs), were used to develop bioactive materials with antioxidant activity. Two types of ethanol fungal extracts from Aspergillus tubingensis G131 were used; a crude (CE*3) and a semi-purified (EP) extract, which presented different antioxidant capacity. Initial degradation temperature of samples with 2% of CE*3 extract were decreased in comparison to the control. Mechanical properties were significantly affected by the incorporation of the fungal extracts, those samples with CE*3 extract presented higher elongation at break due to the presence of melanins, while samples with EP extract showed higher modulus and tensile strength because of the increase in macromolecules interactions product of the hydrophobic character of the extract. Barrier properties were improved due to the low affinity to water of the extract. Antioxidant capacity of films was confirmed by the ABTS method. The addition of fungal metabolites with antioxidant properties to yeast cell wall films is a promising solution for the development of active materials for food contact application increasing shelf life of the products.

The symbiotic community of bacteria and yeast (SCOBY) of Kombucha beverage produces a floating film composed of bacterial cellulose, a distinctive biobased material. In this work, Kombucha fermentation was carried out in six different herbal infusions, where SCOBY was able to synthesise cellulosic films. Infusions of black and green tea, yerba mate, lavender, oregano and fennel added with sucrose (100 g/l) were used as culture media. In all cultures, film production resulted in a maximum after 21 days. Yield conversion, process productivity and antioxidant activity were quantified. Macroscopic and microscopic features of films were determined based on electronic microscopy, calorimetric and mechanical properties and hydration behaviour. Native films from yerba mate had a remarkable antioxidant activity of 93 ± 4% of radical inhibition due to plant polyphenols, which could prevent food oxidation. Results revealed that films retained natural bioactive substances preserving important physicochemical properties, essential for developing active materials.

Nano-biocomposite films based on poly (lactic acid) (PLA) were prepared by adding thymol (8 wt.%) and a commercial montmorillonite (D43B) at different concentrations (2.5 and 5 wt.%). The antioxidant, antimicrobial, and disintegration properties of all films were determined. A kinetic study was carried out to evaluate the thymol release from the polymer matrix into ethanol 10% (v/v) as food simulant. The nanostructured networks formed in binary and ternary systems were of interest in controlling the release of thymol into the food simulant. The results indicated that the diffusion of thymol through the PLA matrix was influenced by the presence of the nanoclay. Disintegration tests demonstrated that the incorporation of both additives promoted the breakdown of the polymer matrix due to the presence of the reactive hydroxyl group in the thymol structure and ammonium groups in D43B. Active films containing thymol and D43B efficiently enhanced the antioxidant activity (inhibition values higher than 77%) of the nano-biocomposites. Finally, the addition of 8 wt.% thymol and 2.5 wt.% D43B significantly increased the antibacterial activity against Escherichia coli and Staphylococcus aureus 8325-4, resulting in a clear advantage to improve the shelf-life of perishable packaged food. Authors would like to thank Spanish Ministry of Economy and Competitiveness (MAT2017-84909-C2-1-R) and Generalitat Valenciana (IDIFEDER/2018/007) for their support of this research. Marina Ramos would like to thank University of Alicante (Spain) for the UAFPU2011-48539721S predoctoral research grant. AJMV thanks ´Coimbra Chemistry Center and Fundação para a Ciência e Tecnologia (FCT) for the financial support through the programmes UID/QUI/UI0313/2020 and COMPETE.

The development of biodegradable materials from microbial exopolysaccharides has extraordinary potential to be applied in food packaging. Kombucha tea is a fermented drink produced by a symbiotic community of bacteria and yeasts, where a by-product based on bacterial cellulose is generated at the surface of the beverage. In this work, novel materials based on the integral kombucha tea by-product were developed from the floating and the intentionally submerged discs of biomass. Each disc was dispersed in water and subjected to ultrasonic homogenization. Films obtained by casting exhibited high homogeneity without cracks with a microstructure composed by a homogeneous and continuous cellulosic matrix of ribbon-shaped nanofibers. Infrared spectroscopy and thermogravimetric analyses indicated the further presence of low and high molecular weight compounds. The increase in glycerol content in the film decreased glass transition temperature and increased flexibility, hydration, and water vapor permeability. Films obtained from submerged discs had an additional plasticization given by substances incorporated during the immersion in the culture medium. Both types of films made from the floating and the submerged disc had a natural and remarkable antioxidant activity of 69 ± 2% and 72 ± 2% of radical inhibition, respectively, probably due to polyphenols or other compounds from the culture medium. Results revealed that using the integral cellulosic by-product of kombucha tea to prepare films could be advantageous due to the cost-effective process (no separation, no purification), interesting physical-chemical properties, and the retention of natural bioactive substances. Fil: Ramírez Tapias, Yuly Andrea. Universidad Nacional de Quilmes. Departamento de Ciencia y Tecnología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Peltzer, Mercedes Ana. Universidad Nacional de Quilmes. Departamento de Ciencia y Tecnología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Delgado, Juan Francisco. Universidad Nacional de Quilmes. Departamento de Ciencia y Tecnología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Salvay, Andrés Gerardo. Universidad Nacional de Quilmes. Departamento de Ciencia y Tecnología; Argentina

Thymol and silver nanoparticles (Ag-NPs) were used to develop poly(lactic acid) (PLA)-based films with antioxidant and antibacterial performance. Different amounts of thymol (6 and 8 wt%) and 1 wt% Ag-NPs were added to PLA to produce the active films. Ag-NPs and thymol were successfully identified in the nanocomposite structures using spectroscopic techniques. A kinetic study was performed to evaluate the release of thymol and Ag-NPs from the nanocomposites to an aqueous food simulant (ethanol 10%, v/v) at 40 &deg, C. The diffusion of thymol from the polymer matrix was affected by the presence of non-migrating Ag-NPs, which showed non-Fickian release behavior. The ternary system including 1 wt% Ag-NPs and 8 wt% thymol showed clear antibacterial performance by reducing the cell viability of Escherichia coli and Staphylococcus aureus by around 40% after 3 and 24 h of storage at 4, 25, and 37 &deg, C compared to neat PLA. Significant antioxidant behavior of all active films was also confirmed using the 2,2-diphenyl-1-picrylhydrazyl (DPPH) method. The obtained nanocomposite films based on PLA and the addition of Ag-NPs and thymol were proven to have combined antioxidant and antibacterial performance, with controlled release of thymol. These formulations have potential applications in the development of innovative and customized active packaging systems to increase the shelf-life of food products.

There is a strong public concern about plastic waste, which promotes the development of new biobased materials. The benefit of using microbial biomass for new developments is that it is a completely renewable source of polymers, which is not limited to climate conditions or may cause deforestation, as biopolymers come from vegetal biomass. The present review is focused on the use of microbial biomass and its derivatives as sources of biopolymers to form new materials. Yeast and fungal biomass are low-cost and abundant sources of biopolymers with high promising properties for the development of biodegradable materials, while milk and water kefir grains, composed by kefiran and dextran, respectively, produce films with very good optical and mechanical properties. The reasons for considering microbial cellulose as an attractive biobased material are the conformational structure and enhanced properties compared to plant cellulose. Kombucha tea, a probiotic fermented sparkling beverage, produces a floating membrane that has been identified as bacterial cellulose as a side stream during this fermentation. The results shown in this review demonstrated the good performance of microbial biomass to form new materials, with enhanced functional properties for different applications.

The use of renewable resources to develop food contact materials, such as proteins or polysaccharides, and the use of industrial residues for alternative applications are trending topics for researchers and the industry. Yeast cell wall (YCW) is a very rich waste from the yeast extract industry. Due to this, the aim of this work is to develop new biodegradable films based on residual YCW and the study of the effect of plasticization on films properties. Residual YCW was used as base matrix and different concentrations of glycerol (0, 15, 25 and 35 wt%) were tested to obtain casted films. Homogeneous and yellow-brownish films, which allow seeing through them, were obtained from the YCW. Total soluble matter demonstrated that glycerol enhanced solubility of films but glycerol was retained in the polymer matrix. TGA studies indicated that YCW films exhibited substantial degradation at temperatures above 180 °C. FTIR spectra of the casted films were representative of yeast cell wall material and SEM photographs showed that cell wall maintained their shape after film formation. As expected, Young’s modulus and tensile strength values were decreased with the increasing amount of glycerol. However, elongation at break was not increased further with higher concentration of plasticizer and the addition of 15 wt% of glycerol seemed to be enough to improve mechanical properties. The linear increment of water vapour permeability with glycerol concentration was produced by the increase in water solubility in the film. Therefore, based on solubility in water, mechanical, and barrier properties, it is possible to propose yeast cells residues as film-forming material for biodegradable film developments. Fil: Peltzer, Mercedes Ana. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Quilmes. Departamento de Ciencia y Tecnología; Argentina Fil: Salvay, A.G.. Universidad Nacional de Quilmes. Departamento de Ciencia y Tecnología; Argentina Fil: Delgado, Juan Francisco. Universidad Nacional de Quilmes. Departamento de Ciencia y Tecnología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: de la Osa, Orlando. Universidad Nacional de Quilmes. Departamento de Ciencia y Tecnología; Argentina Fil: Wagner, Jorge Ricardo. Universidad Nacional de Quilmes. Departamento de Ciencia y Tecnología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina

Characterization of films made of Saccharomyces cerevisiae biomass was performed so as to better understand their properties. The treated yeast biomass, named HTH, was prepared by subsequent steps including a first homogenization, heat treatment and final homogenization. Glycerol was added as plasticizer and films were evaluated using different techniques to measure mechanical behaviour, thermal properties and water sorption. Temperature of maximum decomposition rate was found near 300 °C, while the gradually disappearance of amide II band (1543 cm−1) occurred from 225 °C, identified by FTIR spectra of residues of thermally treated films by TGA. A glass transition at 64.5 ± 3.0 °C and two low energy endotherms at 61.2 ± 2.3 and 106.1 ± 0.7 °C were determined in completely dehydrated films without glycerol. When glycerol content was increased the glass transition temperature was shifted to lower values, a maximum elongation of 12% was reached, Young's modulus decreased from 88 to 9 MPa and the water uptake of films raised from 0.49 to 0.79 g H2O/g of dry matter. The characterization of yeast biodegradable films provided evidence of their properties for a potential future use in packaging industry. Industrial relevance: The development of biodegradable films based on yeast biomass carries many advantages to the food industry, such as, the possibility of using commercial pressed baker's yeast or an industrial residue from brewing industry, the use of a low-cost sources and the application of environmentally friendly procedures. The methodologies applied for the development of the film forming dispersion, high pressure homogenization and thermal treatment, are able to be scaled-up to an industrial level. Fil: Delgado, Juan Francisco. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Quilmes. Departamento de Ciencia y Tecnología. Área Ingeniería en Alimentos; Argentina Fil: Peltzer, Mercedes Ana. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Quilmes. Departamento de Ciencia y Tecnología. Área Ingeniería en Alimentos; Argentina Fil: Salvay, Andrés Gerardo. Universidad Nacional de Quilmes. Departamento de Ciencia y Tecnología. Área Ingeniería en Alimentos; Argentina Fil: de la Osa, Orlando. Universidad Nacional de Quilmes. Departamento de Ciencia y Tecnología. Área Ingeniería en Alimentos; Argentina Fil: Wagner, Jorge Ricardo. Universidad Nacional de Quilmes. Departamento de Ciencia y Tecnología. Área Ingeniería en Alimentos; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina

Research on biodegradable films is a topic of strategical interest in the field of food science and technology. These films are membranes conformed by biopolymers that interact strongly with water and they generally require the addition of plasticizer in order to improve its integrity and mechanical properties. The study of the hydration and water transfer properties through these films, as well as understanding in what way the thickness and the addition of the plasticizer affect these properties, is essential for a better knowledge and optimization of the required protective function of these membranes. In this work the hydration kinetics and water transport through biodegradable films obtained from yeast biomass were studied, in order to know the performance against changes in thickness and glycerol content. Hydration kinetics experiments allowed obtaining solubility of water in the matrix film, and the diffusion coefficient. Results demonstrated that when glycerol content was increased, the solubility of water increased while diffusion remained constant. Moreover, when the film thickness was grown, the solubility of water decreased but the diffusion increased. Experimental water vapour permeability obtained through traditional cup method was compared to the theoretical permeability calculated by multiplying diffusion coefficient and water solubility. The good agreement observed between both values allowed the analysis of how solubility and diffusion contributed to permeability. As a result this study revealed that the increment of permeability with the plasticizer content was due to the increase in solubility, while the effect of the thickness increasing permeability was dominated by diffusion. Fil: Delgado, Juan Francisco. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Quilmes. Departamento de Ciencia y Tecnología; Argentina Fil: Peltzer, Mercedes Ana. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Quilmes. Departamento de Ciencia y Tecnología; Argentina Fil: Wagner, Jorge Ricardo. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Quilmes. Departamento de Ciencia y Tecnología; Argentina Fil: Salvay, Andrés Gerardo. Universidad Nacional de Quilmes. Departamento de Ciencia y Tecnología; Argentina

D-limonene is a monoterpene obtained from a variety of citrus fruit peel oil which is the most important residue in citrus industry. It is food grade and presents antioxidant properties. The use of antioxidants additives in polymers for food packaging is a common practice to reduce their potential thermo-oxidative degradation during processing and they could also prevent the food oxidation reducing the direct addition of antioxidants to the food. Among them, the great interest towards the use of renewable natural resources in the food packaging industry makes natural antioxidants candidates to stabilize biodegradable polymer formulations. In this sense, poly(lactic acid) (PLA) seems to be the most attractive biodegradable polymer for food packaging industry. Thus, the aim of this work was to study the thermal degradation of PLA films stabilized with D-limonene. Kinetic parameters were obtained by thermogravimetric analysis (TGA) in dynamic mode and the apparent activation energies (Ea) were calculated by the Friedman method. The comparison of Ea between PLA stabilized with D-limonene and non-stabilized polymer furnished information on the thermal stabilization performance. The results indicate that D-limonene shows good performance in the PLA stabilization and therefore the possibility of its use as additive intended for food packaging materials., This research was supported by the Ministry of Science and Innovation of Spain (MAT2011-28468-C02-01 and MAT2011-28468-C02-02). Marina Arrieta is granted by Generalitat Valenciana (Spain) with a Santiago Grisolía Fellowship.

Background: β-glucans are naturally occurred polysaccharides of glucose units, present in the cell wall of various living organisms such as bacteria, yeast, fungus and plants, in particular cereals (oat and barley). β-glucans are considered as GRAS and are currently used as texturing agents in the food industry. Alternative applications of β-glucan are the development of bio-based by using isolated β-glucan or in combination with other biopolymers. Objective: The aim of this work is to review all the potentiality that β-glucans present to develop bio-based films for food contact materials and medical applications. Results: It was very well described that the intake of β-glucan is related to the decrease of plasma cholesterol and stimulation of the immune system, depending on the β-glucan na-ture. However, during the last decade there has been an impressive grow on the interest on the development and use of bio-based films and packaging materials. Yeast cell wall, that consist of β-1,3-glucan network crosslinked to β-1,6-glucan, mannoprotein, and a small amount of chitin, are an attractive encapsulation matrix and for film forming preparations. In addition, dispersions of β-glucan from oat cultivars demonstrated to be promising films forming hydrogels, with potential to be used as biodegradable edible packaging film. Indeed, some investigations suggested the production of polysaccharide nanocrystals based on β-1,3-glucan from S. cerevisiae by using an esterification method. Conclusion: β-glucan was found to be a biopolymer with interesting features to be applied in materials science field, food contact and medical applications. Fil: Peltzer, Mercedes Ana. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Quilmes. Departamento de Ciencia y Tecnología; Argentina Fil: Delgado, Juan Francisco. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Quilmes. Departamento de Ciencia y Tecnología; Argentina Fil: Salvay, Andrés Gerardo. Universidad Nacional de Quilmes. Departamento de Ciencia y Tecnología; Argentina Fil: Wagner, Jorge Ricardo. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Quilmes. Departamento de Ciencia y Tecnología; Argentina

The costs of biobased and biodegradable polymers are generally still much higher than that of their traditional polymer counterparts Frequently used in the food packaging field. Although PLA is currently used in the market in several packaging applications,its potential to substitute petrochemical-based polymers has not yet been realized in full perspective. The reinforcing effect of CNC has a large potential inenhancing the crystallinity of PLA that could result in higher tortuosity of the transport path improving the typically low barrier properties of PLA. However, the high polarity of CNC surface should be reduced for the industrial melt processing of PLA?nanocellulose-based materials. The surface functionalization by means of the use of a surfactant is an easy way to improve the dispersion of CNC into PLA matrix.The well dispersion of cellulosic nanoparticles achieved during nanocomposite processing has a large potential in improving the mechanical performance. Additionally, the CNC presence also accelerates the degradation rate of the PLA-based nanocomposites.These bionanocomposites are promising candidates for sustainable post-use waste treatments, such as composting, when short biodegradation times are required like the case of food packaging. Fil: Arrieta, M. P.. Consejo Superior de Investigaciones Científicas; España Fil: Peltzer, Mercedes Ana. Universidad Nacional de Quilmes. Departamento de Ciencia y Tecnología. Área Ingeniería en Alimentos; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: López, J.. Universidad Politécnica de Valencia. Instituto de Tecnología de Materiales; España Fil: Peponi, L.. Consejo Superior de Investigaciones Científicas; España

The migration of antioxidant (AO) agents, carvacrol and thymol, from polypropylene (PP) packaging films containing the studied compounds at 80 g/kg separately and an equimolar mixture of them into food simulants was investigated. Fast and reliable analytical procedures were developed and validated for the analysis of the studied AOs in food simulants. For aqueous food simulants, solid phase extraction followed by GC–MS analysis was performed. Fatty food simulants were directly analysed by GC–MS and HPLC-UV for isooctane and ethanol 950 mL/L, respectively. The release of AOs from the films was dependent on the type of food stimulant and AO incorporated. In particular, high levels of migration were obtained for both AOs into isooctane, showing thymol higher migration. The release kinetics of AOs from PP films showed a Fichian behaviour with diffusion coefficients ranging from 1 to 2 × 10−14 m2/s; except for the diffusion into isooctane where 4-6 higher values were obtained. The antioxidant activity of migration extracts was confirmed by the DPPH method, showing thymol a higher antioxidant capacity especially into isooctane with a 42.2% of inhibition. The obtained results suggest that carvacrol and thymol show a potential use as AOs for active packaging for extending the shelf-life of food products. Fil: Ramos, Marina. Universidad de Alicante; España Fil: Beltran, Ana. Universidad de Alicante; España Fil: Peltzer, Mercedes Ana. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad de Alicante; España Fil: Valente, Arthur J. M.. Universidad de Coimbra; Portugal Fil: Garrigoz, Maria del Carmen. Universidad de Alicante; España

Microorganisms’ biomass is a sustainable and innovative source of biopolymers, such as proteins and polysaccharides, which are suitable for development of biodegradable films. In this work, an alternative material based on the entire biomass of water kefir grains was developed. The whole biomass was submitted to physical treatments of ultrasonic homogenization separated by a thermal treatment at 90 °C. The effect of glycerol on film properties was evaluated. The films obtained exhibited high transparency and homogeneity without cracks. Infrared spectroscopy revealed that the material is constituted basically by the polysaccharide dextran. The increasing plasticiser content decreased glass transition temperature. Indeed, the presence of plasticiser increased the amount of hydration water and the water vapour permeability. Moreover, the addition of 30 wt% of glycerol improved significantly the elasticity of films to 275 ± 15%. Results revealed that water kefir grains biomass is a viable and innovative source of biodegradable materials.

The use of biopolymers obtained from renewable resources is currently growing and they have found unique applications as matrices and/or nanofillers in 'green' nanocomposites. Grafting of polymer c ...

Edible active films based on sodium caseinate (SC) and calcium caseinate (CC) plasticized with glycerol (G) at three different concentrations and carvacrol (CRV) as active agent were prepared by solvent casting. Transparent films were obtained and their surfaces were analysed by optical microscopy and scanning electron microscopy (SEM). The influence of the addition of three different plasticizer concentrations was studied by determining tensile properties, while Fourier transformed infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA) were used to evaluate the structural and thermal behavior of such films. The addition of glycerol resulted in a reduction in the elastic modulus and tensile strength, while some increase in the elongation at break was observed. In general terms, SC films showed flexibility higher than the corresponding CC counterparts. In addition, the presence of carvacrol caused further improvements in ductile properties suggesting the presence of stronger interactions between the protein matrix and glycerol, as it was also observed in thermal degradation studies. FTIR spectra of all films showed the characteristic bands and peaks corresponding to proteins as well as to primary and secondary alcohols. In summary, the best results regarding mechanical and structural properties for caseinates-based films containing carvacrol were found for the formulations with high glycerol concentrations., Marina Patricia Arrieta thanks Fundacion MAPFRE for "Ignacio Hernando de Larramendi 2009- Medio Ambiente" fellowship (MAPFRE-IHL-01). The Spanish Ministry of Economy and Competitiveness is acknowledged by financial support (project Ref. MAT2011-28468-C02-01). Authors thank to Ferrer Alimentacion S.A., for providing caseinates and to Prof. Juan Lopez Martinez (Polytechnic University of Valencia, Spain) for his collaboration and useful discussions.

Active nanocomposite films based on poly(lactic acid) (PLA), thymol and silver nanoparticles (Ag-NPs) were prepared and characterized. PLA films containing 6 and 8 wt% thymol and 1 wt% Ag-NPs were processed by extrusion to obtain binary and ternary formulations. The addition of thymol and Ag-NPs modified the PLA thermal, optical and barrier properties; in particular water vapour permeability (WVP), maintaining oxygen transmission rate (OTR) values unchanged. Homogeneous surfaces in all films were obtained as proved by FESEM micrographs. The presence of the active additives enhanced the disintegration rate of PLA under composting conditions, which was completed in 14 days. Results suggest that these nanocomposite films could be considered promising degradable active packaging materials with low environmental impact. Fil: Ramos, Marina. Universidad de Alicante; España Fil: Fortunati, Elena. Universita Di Perugia; Italia Fil: Peltzer, Mercedes Ana. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Quilmes. Departamento de Ciencia y Tecnologia; Argentina Fil: Jimenez, Alfonso. Universidad de Alicante; España Fil: Kenny, José María. Instituto En Ciencia y Tecnologia de Polimeros; España. Universita Di Perugia; Italia Fil: Garrigós, María Carmen. Universidad de Alicante; España

Biodegradable alternatives to petroleum-based polymers are being developed for food packaging. Saccharomyces cerevisiae has been widely used for the production of fermented beverages and leavened foods. In this work, the application of high pressure homogenisation and a thermal treatment to the yeast biomass was studied to develop biodegradable films. The highest dispersibility indexes of protein (84.5 ± 3.3%), carbohydrates (24.3 ± 1.1%), RNA (40.6 ± 0.9%) and soluble solids released were found at high homogenisation pressure (125 MPa). Combinations of one or two homogenisations and a thermal treatment at 90 °C during 20 minutes were applied and dispersions were fully characterised, focusing on their film-forming capacity. The best combination was homogenisation, heat treatment and a further homogenisation, since it produced films that presented good attributes, great continuity and homogeneity without small cracks. However, hydration of films was increased from 0.31 to 0.48 gH2O/g.d.m with the number of homogenisation processes applied. Results revealed that yeast biomass is a viable source to be used in biodegradable films. Industrial relevance Saccharomyces cerevisiae yeasts have many applications in food industry. The development of biodegradable films based on yeast biomass carries many advantages such as, the possibility of using commercial pressed baker's yeast or an industrial residue from brewing industry, the use of a low-cost sources and the application of environmentally friendly procedures. The methodologies applied for the development of the film forming dispersion, high pressure homogenisation and thermal treatment, are able to be scaled-up to an industrial level. Fil: Delgado, Juan Francisco. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Quilmes. Departamento de Ciencia y Tecnología; Argentina Fil: Sceni, Paula. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Quilmes. Departamento de Ciencia y Tecnología; Argentina Fil: Peltzer, Mercedes Ana. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Quilmes. Departamento de Ciencia y Tecnología; Argentina Fil: Salvay, Andrés Gerardo. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Quilmes. Departamento de Ciencia y Tecnología; Argentina Fil: de la Osa, Orlando. Universidad Nacional de Quilmes. Departamento de Ciencia y Tecnología; Argentina Fil: Wagner, Jorge Ricardo. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Quilmes. Departamento de Ciencia y Tecnología; Argentina

Nanocellulose has gained considerable attention in the food packaging industry as a nanoreinforcement for polymer matrices, mainly those biobased and biodegradable. Derived from the most abundant polymeric resource in nature and with inherent biodegradability, nanocellulose is an interesting nanofiller for the development of bionanocomposites processed by traditional processing techniques. Due to the high number of hydroxyl groups on its surface, nanocellulose is easy to functionalize, mainly to improve its dispersion within the polymer matrix. Well-dispersed nanocellulose is able to enhance several properties of polymers, including thermal, mechanical, barrier, and surface wettability properties, as well as control of active compound release, etc. This chapter reviews the most relevant processing aspects of nanocellulose-based polymeric blends such as thermal stability and nanofiller dispersion. It also summarizes recent developments in biobased and biodegradable nanocellulose-based polymeric blends for food packaging with an emphasis on bionanocomposite properties and a focus on the sustainable food packaging field.

Antimicrobial active films based on polypropylene (PP) were prepared by incorporating thymol and carvacrol at three different concentrations: 4, 6 and 8 wt.% of both additives as well as an equimolar mixture of them. A complete thermal, structural, mechanical and functional characterization of all formulations was carried out. SEM micrographs showed certain porosity for films with high additives concentrations. A decrease in elastic modulus was obtained for the active formulations compared with neat PP. The presence of additives did not affect the thermal stability of PP samples, but decreased PP crystallinity and oxygen barrier properties. The presence of thymol and carvacrol also increased stabilization against thermo-oxidative degradation, with higher oxidation induction parameters. Finally, thymol showed higher inhibition against bacterial strain present in food compared with carvacrol, leading to higher antimicrobial activity. The obtained results proved the permanence of certain amounts of the studied additives in the polymer matrix after processing making them able to be used as active additives in PP formulations.

Films of neat and plasticized biodegradable poly(lactic acid) (PLA) matrices containing anionic conjugated polyelectrolytes, poly[9,9-bis(4-phenoxybutylsulfonate)]fluorene-2,7-diyl-alt-arylenes, with 1,4-phenylene and 4,4″-p-terphenylene, respectively, as arylene groups or a neutral poly(9,9-dialkylfluorene) for comparison were prepared by solution casting. These films were characterized using differential scanning calorimetry, thermogravimetry, scanning electron microscopy and fluorescence spectroscopy. In addition, the effects of plasticizer on the thermal properties and the oxygen permeability of the PLA films were measured through the oxygen transmission rate. Results show that it is possible to obtain thin, optically transparent and luminescent films with potential in oxygen sensing, exhibiting good thermal and photochemical stability. At high polyelectrolyte content, evidence is found for phase separation and aggregate formation and it is no longer possible to obtain completely homogeneous films. The possibility of incorporating the cationic metal complex tris(2,2′-bipyridyl)ruthenium(II) into plasticized PLA films containing conjugated polyelectrolytes for dual-wavelength ratiometric luminescence sensing is also discussed. Copyright © 2012 Society of Chemical Industry

The use of hydroxytyrosol (3,4-dihydroxy-phenylethanol) as a potential alternative to synthetic compounds in the melt stabilization of polyolefins is considered. Hydroxytyrosol was found to play a role in enhancing the oxidative stability of olive oil, and a similar reduction in polyolefins’ thermo-oxidative degradation during processing is expectable. Rheological tests (melt flow index and viscosity vs. shear rate) showed the good antioxidant performance of hydroxytyrosol during polypropylene processing as was also demonstrated by the increase in apparent activation energies and oxidation induction parameters after addition to polypropylene (0.1 wt%). Results were compared to those obtained for a commercial synthetic phenolic antioxidant and for a natural compound widely used in polymer stabilization (α-tocopherol). The main conclusion of this work is the good performance of hydroxytyrosol in polypropylene stabilization during processing and consequently the possibility of its use in formulations with improved resistance to oxidative degradation.

Oxidation thermal parameters on samples of polypropylene (PP) stabilized with hydroxytyrosol were determined. For comparison purposes, -tocopherol and a synthetic phenolic commercial antioxidant (Irganox 1076), were also analyzed. Oxidation induction time (OIt) and oxidation induction temperature (OIT) were determined by differential scanning calorimetry (DSC). The addition of hydroxytyrosol 0.1 mass% to PP was enough to obtain efficient stabilization during processing. Certain decrease in stabilizing properties of natural antioxidants was observed for compression moulded materials at high temperatures. However, these samples were still efficiently stabilized in comparison to the pure material. Hydroxytyrosol showed good performance as polypropylene antioxidant and it might be considered as promising alternative to the use of phenolic synthetic compounds.

The efficacy of UV light for inactivating E. coli (ATCC 25922) and E. coli O157:H7 (EDL 933) was examined in fruit juices (orange, apple, and multifruit) with different absorptivities under several operating conditions (liquid film thickness and agitation rate). The juices were inoculated with two bacterial concentrations (10(5) and 10(7) CFU/ml) and were treated using a UV desinfection unit at 254 nm; UV doses ranged from 0 to 6 J/cm2. The effect of the culture medium, tryptone soy agar (TSA) and sorbitol MacConkey agar (SMAC), on the recovery of E. coli strains exposed to UV radiation was also analyzed. The most suitable culture medium for recovery of E. coli strains in juices exposed to UV radiation was TSA. Values of D (radiation dose [joules per square centimeter] necessary to decrease the microbial population by 90%) obtained in all juices assessed were higher in TSA than in SMAC. In the juices analyzed, stirring of the medium exposed to UV radiation and reducing liquid film thickness (to 0.7 mm) produced the highest bactericidal effect. A linear relationship was found between the D-values obtained and the absorptivity coefficients for all the juices. The higher the absorbance of the medium, the greater the values of D required to inactivate E. coli strains by UV radiation. An equation was developed to describe the relationship of the fraction of energy absorbed by the system (absorbed energy factor [AEF]), the thickness of the film exposed to UV radiation, and the absorptivity coefficient of the juices. A linear relationship was found between D and AEF in the different juices tested., Centro de Investigación y Desarrollo en Criotecnología de Alimentos

Quinoa has been identified as a promising source of food. Reports in the literature have focused mainly on agronomic potential, composition, nature of the starch and protein quality. Other aspects related with drying and storing of quinoa seed have received less attention. Moisture sorption isotherms constitute an essential part of the theory of drying and in the study of storage of dehydrated foods. Vapour water sorption of quinoa grains was determined at 20, 30 and 40 °C in the range of 0.089–0.851 water activity ( a w ) by means of the gravimetric method. Experimental curves were fitted to one three-parameter equation (Guggenheim–Anderson–de Boer, GAB equation). The equilibrium values and temperature shifts were modelled with a three-parameter equation in the approximate moisture content range of 0.02–0.18 (g water/g dry matter). An analytical expression to calculate the isosteric heat of sorption and its moisture content dependence was used and the results were compared with the isosteric heat calculated from the experimental equilibrium data by means of the Clausius–Clapeyron equation. The GAB model describe the sorption isotherms of quinoa grains at different temperatures in the range of a w investigated, the sorption areas obtained from the GAB equation were comparable with other sorption areas reported in the literature for various cereal grains and the effect of temperature on water sorption isotherms is adequately describes by an equation based on the enthalpy-entropy compensation.

Many industrial sectors have been subjected in recent years to an important evolution by making great efforts in developing degradable biological materials without significant environmental pollution to replace petrochemical-based traditional plastics. Among the numerous bio-based and biodegradable polymers, poly(lactic acid) (PLA) is currently the most promising and popular material with the brightest development prospect and it is considered the “green” eco-friendly material. In particular in the food packaging sector it has been approved by the US Food and Drug Administration (FDA) for use as a food contact material. This chapter will provide information on the regulations, directives and standards related to biodegradable food contact materials, biodegradability and compostability, nanotechnology and those applied to the study of their environmental impact by the Life Cycle Assessment (LCA). We will focus on the food packaging area, since it is where most of the PLA uses are better regulated, but the information could be applied to other industrial sectors.

Ternary nano-biocomposite films based on poly(lactic acid) (PLA) with modified cellulose nanocrystals (s-CNC) and synthesized silver nanoparticles (Ag) have been prepared and characterized. The functionalization of the CNC surface with an acid phosphate ester of ethoxylated nonylphenol favoured its dispersion in the PLA matrix. The positive effects of the addition of cellulose and silver on the PLA barrier properties were confirmed by reductions in the water permeability (WVP) and oxygen transmission rate (OTR) of the films tested. The migration level of all nano-biocomposites in contact with food simulants were below the permitted limits in both non-polar and polar simulants. PLA nano-biocomposites showed a significant antibacterial activity influenced by the Ag content, while composting tests showed that the materials were visibly disintegrated after 15 days with the ternary systems showing the highest rate of disintegration under composting conditions. © 2013 Elsevier Ltd. All rights reserved.

Novel nano-biocomposite films based on poly (lactic acid) (PLA) were prepared by incorporating thymol, as the active additive, and modified montmorillonite (D43B) at two different concentrations. A complete thermal, structural, mechanical and functional characterization of all nano-biocomposites was carried out. Thermal stability was not significantly affected by the addition of thymol, but the incorporation of D43B improved mechanical properties and reduced the oxygen transmission rate by the formation of intercalated structures, as suggested by wide angle X-ray scattering patterns and transmission electron microscopy images. The addition of thymol decreased the PLA glass transition temperature, as the result of the polymer plasticization, and led to modification of the elastic modulus and elongation at break. Finally, the amount of thymol remaining in these formulations was determined by liquid chromatography (HPLC-UV) and the antioxidant activity by the DPPH spectroscopic method, suggesting that the formulated nano-biocomposites could be considered a promising antioxidant active packaging material. Spanish Ministry of Economy and Competitiveness (MAT2011-28468-C02-01). Marina Ramos would like to thank University of Alicante (Spain) for UAFPU2011-48539721S pre-doctoral research grant.

Biopolymers, such as poly(lactic acid) (PLA), have been proposed as environmentally-friendly alternatives in applications such as food packaging. In this work, silver nanoparticles and thymol were used as active additives in PLA matrices, combining the antibacterial activity of silver with the antioxidant performance of thymol. The combined action of both additives influenced PLA thermal degradation in ternary systems. DSC results showed that the addition of thymol resulted in a clear decrease of the glass transition temperature (Tg) of PLA, suggesting its plasticizing effect in PLA matrices. Slight modifications in mechanical properties of dog-bone bars were also observed after the addition of the active components, especially in the elastic modulus. FESEM analyses showed the good distribution of active additives through the PLA matrix, obtaining homogenous surfaces and highlighting the presence of silver nanoparticles successfully embedded into the bulk matrix. Degradation of these PLA-based nanocomposites with thymol and silver nanoparticles in composting conditions indicated that the inherent biodegradable character of this biopolymer was improved after this modification. The obtained nanocomposites showed suitable properties to be used as biodegradable active-food packaging systems with antioxidant and antimicrobial effects. Authors would like to thank Spanish Ministry of Economy and Competitiveness for financial support (MAT-2011-28468-C02-01). Moreover, Marina Ramos would like to thank University of Alicante (Spain) for UAFPU2011-48539721S predoctoral research grant.

Active edible films were prepared by adding carvacrol into sodium caseinate (SC) and calcium caseinate (CC) matrices plasticized with two different glycerol concentrations (25 and 35 wt%) prepared by solvent casting. Functional characterisation of these bio-films was carried out by determination of some of their physico-chemical properties, such as colour, transparency, oxygen barrier, wettability, dye permeation properties and antibacterial effectiveness against Gram negative and Gram positive bacteria. All films exhibited good performance in terms of optical properties in the CIELab space showing high transparency. Carvacrol was able to reduce CC oxygen permeability and slightly increased the surface hydrophobicity. Dye diffusion experiments were performed to evaluate permeation properties. The diffusion of dye through films revealed that SC was more permeable than CC. The agar diffusion method was used for the evaluation of the films antimicrobial effectiveness against Escherichia cell and Staphylococcus aureus. Both SC and CC edible films with carvacrol showed inhibitory effects on both bacteria. (C) 2013 Elsevier Ltd. All rights reserved., This research was supported by the Ministry of Science and Innovation of Spain through the projects MAT2011-28468-C02-01, MAT2011-28468-C02-02 and HP2008-0080. M.P. Arrieta thanks Fundacion MAPFRE for "Ignacio Hernando de Larramendi 2009-Medio Ambiente" fellowship (MAPFRE-IHL-01). Authors thank Ferrer Alimentacion S.A., for providing the caseinates powders.

Hydrogenated amorphous carbon (a-C:H) films were grown on a poly(lactic acid) (PLA) substrate by means of a radiofrequency plasma-enhanced chemical vapour deposition (rf-PECVD) technique with different deposition times (5, 20 and 40 min). The main goal of this treatment was to increase the barrier properties of PLA, maintaining its original transparency and colour as well as controlling interactions with food simulants for packaging applications. Morphological, chemical, and mechanical properties of PLA/a-C:H systems were evaluated while permeability and overall migration tests were performed in order to determine the effect of the plasma treatment on the gas-barrier properties of PLA films and their application in food packaging. Morphological results suggested a good adhesion of the deposited layers onto the polymer surface and the samples treated for 5 and 20 min only slightly darkened the PLA film. X-ray photoelectron spectroscopy revealed that the structural properties of the carbon layer deposited onto the PLA film depend on the exposure time. PLA/a-C:H system treated for 5 min showed the highest barrier properties, while none of the studied samples exceeded the migration limit established by the current legislation, suggesting the suitability of these materials in packaging applications. Authors gratefully acknowledge the financial support from the National Consortium of Materials Science and Technology (INSTM) and Spanish Ministry of Economy and Competiveness (MAT2011-28468-C02-01).

Poly(lactic acid) (PLA)-based high performance nano-biocomposites were prepared to be used in active food packaging. Pristine (CNC) and surfactant modified cellulose nanocrystals (s-CNC) with silver (Ag) nanoparticles were used as the matrix modifiers. Binary and ternary systems were prepared. Morphological investigations revealed the good distribution of silver nanoparticles in PLA ternary systems. The combination of s-CNC and Ag nanoparticles increased the barrier effect of the produced films while the results of overall migration for the PLA nano-biocomposites revealed that none of the samples exceeded the overall migration limit, since results were well below 60 mg kg−1 of simulant. The authors gratefully acknowledge the financial support from the National Consortium of Materials Science and Technology (INSTM) and Spanish Ministry of Science and Technology (Project MAT2011-28640-C02-01).

Polymers derived from renewable resources are now considered as promising alternatives to traditional petro-polymers as they mitigate current environmental concerns (raw renewable materials/biodegradability). D-limonene can be found in a variety of citrus, indeed is the main component of citrus oils and one of most important contributors to citrus flavor. The incorporation of limonene in PLA matrix was evaluated and quantified by Pyrolysis Gas Chromatography Mass Spectrometry (Py-GC/MS). Transparent films were obtained after the addition of the natural compound. Mechanical properties were evaluated by tensile tests. The effect of limonene on mechanical properties of PLA films was characterized by an increase in the elongation at break and a decrease in the elastic modulus. The fracture surface structure of films was evaluated by scanning electron microscopy (SEM), and homogeneous surfaces were observed in all cases. Barrier properties were reduced due to the increase of the chain mobility produced by the D-limonene. (C) 2013 Elsevier Ltd. All rights reserved., This research was supported by the Ministry of Science and Innovation of Spain (MAT2011-28468-C02-02). Marina P. Arrieta thanks Generalitat Valenciana (Spain) for a Santiago Grisolia Fellowship. Authors thank Professor Alfonso Jimenez from the University of Alicante, for his useful discussions.

Active packaging is becoming an emerging food technology to improve quality and safety of food products. One of the most common approaches is based on the release of antioxidant/antimicrobial compounds from the packaging material. In this work an antifungal active packaging system based on the release of carvacrol and thymol was optimized to increase the post-harvest shelf life of fresh strawberries and bread during storage. Thermal properties of the developed packaging material were determined by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). Volatile compounds in food samples contained in active packaging systems were monitored by using headspace solid phase microextraction followed by gas chromatography analysis (HS-SPME- GC-MS) at controlled conditions. The obtained results provided evidences that exposure to carvacrol and thymol is an effective way to enlarge the quality of strawberries and bread samples during distribution and sale.

The aim of this paper is to report the impact of the addition of cellulose nanocrystals on the barrier properties and on the migration behaviour of poly(lactic acid), PLA, based nano-biocomposites prepared by the solvent casting method. Their microstructure, crystallinity, barrier and overall migration properties were investigated. Pristine (CNC) and surfactant-modified cellulose nanocrystals (s-CNC) were used, and the effect of the cellulose modification and content in the nano-biocomposites was investigated. The presence of surfactant on the nanocrystal surface favours the dispersion of CNC in the PLA matrix. Electron microscopy analysis shows the good dispersion of s-CNC in the nanoscale with well-defined single crystals indicating that the surfactant allowed a better interaction between the cellulose structures and the PLA matrix. Reductions of 34% in water permeability were obtained for the cast films containing 1 wt.% of s-CNC while good oxygen barrier properties were detected for nano-biocomposites with both 1 wt.% and 5 wt.% of modified and un-modified cellulose nanocrystals, underlining the improvement provided by cellulose on the PLA films. Moreover, the migration level of the studied nano-biocomposites was below the overall migration limits required by the current normative for food packaging materials in both non-polar and polar simulants.

The migration behaviour of low molecular weight compounds from food packaging materials is one of the key issues in assessing the possibility of use in such applications. The aim of this work was to study the migration of carvacrol (1% and 2% w/w) when added to high-density polyethylene. All materials were exposed to the food simulants olive oil and distilled water separately at 40 degrees C and 25 degrees C. Three significant variables influencing the migration process were considered: incubation temperatures, the initial concentration of antioxidant, and the type of simulant (oil and aqueous). The amount of carvacrol migrating to olive oil was significantly higher than in water because of the higher solubility of this antioxidant in oil. Experimental results agreed reasonably well with those obtained by the application of a simple model derived from Fick's Second Law. Carvacrol could therefore be used in active packaging formulations as its release from the polymer matrix can be controlled.

Active packaging is becoming an emerging food technology to improve quality and safety of food products. One of the most common approaches is based on the release of antioxidant/a ntimicrobial compounds from the packaging material. In this work an antifungal active packaging system based on the release of carvacrol and thymol was optimized to increase the post-harvest shelf life of fresh strawberries and bread during storage. Thermal properties of the developed packaging material were determined by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). Volatile compounds in food samples contained in active packaging systems were monitored by using headspace solid phase microextraction followed by gas chromatography analysis (HS-SPME-GC-MS) at controlled conditions. The obtained results provided evidences that exposure to carvacrol and thymol is an effective way to enlarge the quality of strawberries and bread samples during distribution and sale.