Frédéric Debeaufort

Edible films and coatings: tomorrow's packagings: a review

The quality of food product depends on organoleptic, nutritional, and hygienic characteristics, but these evolve during storage and commercialization. Such changes are mainly due to exchanges between foods and surrounding media, or migrations between the different components in a composite food. Many physical and chemical processes, such as sterilization, high pressure, radiations or actives agents, were developed to steady foods and thus to preserve food quality. However, the use of a performing package is necessary in the ultimate step of the preservation process. Therefore, packaging is preponderent for the durability of food quality. The performance of synthetic packaging materials is appraised by their efficiency to reduce mass transfers between food and storage medium, that is, by the determination of their permeabilities. The constant progress in synthetic packagings, such as resins, cellulosic and plastic films, permitted the use of composite (copolymer) and/or multilayered film packagings, which are able to significantly reduce gas and solute transfers selectively. However, the suitability of plastic films is not universal. The combination of synthetic and edible packagings was proposed to increase the efficiency of food quality preservation by the packaging. 1 In other respects, edible packagings are nonpollutant products because they consist of natural and biodegradable substances from agriculture. Thus, they contribute to the protection of the environment. Over 90 patents and scientific papers concerning the manufacture of edible packaging have been published since 1990. Most of this work deals with water vapor transfers, but some other potential applications exist. Indeed, edible packagings can be used to encapsulate aroma compounds, 2,3,4 antioxydants, antimicrobial agents, 5 pigments, ions that stop browning reactions 6 or nutritional substances such as vitamins. 7

Factors Affecting the Moisture Permeability of Lipid-Based Edible Films: A Review

Referee: Dr. Aris Gennadios, Senior Manager, Materials Science, Research and Development, Banner Pharmacaps Inc., P.O. Box 2210, 27261-2210, 4125 Premier Drive, High Point, NC 27265-8144 Moisture transfers inside food products could be controlled or limited by the use of edible films. These are usually based on hydrophobic substances such as lipids to improve barrier efficiency. Water permeability of films is affected by many factors, depending on both the nature of barrier components, the film structure (homogeneous, emulsion, multilayer, etc.), crystal type, shape, size and distribution of lipids, and thermodynamics such as temperature, vapor pressure, or the physical state of water in contact to the films. After a brief presentation of lipids and hydrophobic substances used as moisture barrier, cited in the scientific literature, this article reviews all of the parameters affecting barrier performances of edible films and coatings.

Lipid hydrophobicity, physical state and distribution effects on the properties of emulsion-based edible films

Abstract Addition of lipids to polysaccharide-based films is necessary to improve water vapor barrier properties but it leads to a decrease of mechanical properties. Model emulsified edible films mainly composed of methylcellulose (film-forming substance) and lipid mixtures (moisture barrier) were prepared. The effect of the physicochemical characteristics of the lipid phase (hydrophobicity and physical state) and of its distribution within the methylcellulose-matrix on the mechanical and water vapor barrier film properties was investigated. The nature of the lipid phase had little influence on mechanical properties of emulsified films, but had a substantial effect on the water vapor barrier efficiency. Alkanes had moisture barrier efficiencies better than those of triglycerides. The solid–liquid ratio of the lipid phase had little influence on film mechanical properties because totally liquid lipids had a lubricant effect. Solid fat content (SFC) did not affect significantly ( P >0.05) the moisture barrier efficiency, because water vapor could pass through the hydrophilic methylcellulose. SFC increased the opacity of film. The distribution of the fat globules into the methylcellulose matrix affected only the elongation of films.

Wine Oxidation and the Role of Cork

The present review aims to show the state of the art of oxidation mechanisms occurring especially in white wines by taking into account knowledge from different fields in relation to the subject. It is therefore divided into three main parts. First, the mechanisms of oxidation relevant to white wine are discussed in the light of recent scientific literature. Next, the phenomenon of oxygen solubility in wine during the winemaking process, and in particular during bottling is stated theoretically as well as practically. Finally, the aspect of wine conservation after bottling is examined with respect to mass transfers which may occur through the closure, with a special emphasis on cork. Currently, specific physico-chemical properties still make cork closures the most important closure type used for the wine market, and especially for high quality wines. This final section will also include a review of studies performed on this subject, which have been analyzed in detail from a theoretical mass transfer point of view, in order to assess the extent to which the proposed scientific tools and the observed tendencies are relevant to progress in the understanding of the impact of this parameter on the behavior of a wine.

Water vapor permeability and diffusivity through methylcellulose edible films

Abstract A model edible film made with methylcellulose was studied for its water vapor barrier properties. The steady-state water vapor transmission rate (WVTR) increased with both the water vapor pressure gradient and the initial water content before permeation. A decrease in water diffusion with increasing moisture content was due to a clustering phenomenon of water molecules within the film. Water concentration profiles within the film were estimated from the sorption isotherm, and differed from the theoretical linear profile based on Ficks first law. The WVTR and the diffusivity depended strongly on the water concentration because of interactions between water molecules and the polymer matrix. Thus water vapor permeability (WVP) calculations used for synthetic polymeric packaging and based on Ficks and Henrys laws do not apply for methylcellulose edible films.

Importance of Surface Tension Characterization for Food, Pharmaceutical and Packaging Products: A Review

This article reviews the various theoretical approaches that have been developed for determination of the surface tension of solids, and the applications to food industrial products. The surface tension of a solid is a characteristic of surface properties and interfacial interactions such as adsorption, wetting or adhesion. The knowledge of surface tension is thus of great interest for every domain involved in understanding these mechanisms, which recover a lot of industrial investigations. Indeed, it is the case for the packaging industry, the food materials science, the biomedical applications and the pharmaceutical products, cleaning, adhesive technology, painting, coating and more generally all fields in relation with wettability of their systems. There is however no direct method for measurements of surface tension of solids, except the contact angle measurements combined with an appropriate theoretical approach are indirect methods for estimation of surface tension of solids. Moreover, since the publication by Young (1805) who developed the basis of the theory of contact angle some two hundred years ago, measurements and interpretations are still discussed in scientific literature, pointing out the need to better understand the fundamental mechanisms of solid-liquid interfacial interactions. Applications of surface tension characterization in the field of food materials science are detailed, especially for packaging and coating applications, which recover different actual orientations in order to improve process and quality.

Lipid-Based Edible Films and Coatings

The quality of food products depends on their organoleptic, nutritional, and microbiological properties, all of which are subject to dynamic changes during storage and distribution. Such changes are mainly due to interactions between foods and their surrounding environment or to migration between different components within a composite food.

Effect of relative humidity on carvacrol release and permeation properties of chitosan based films and coatings.

The influence of water vapour conditions on mass transport and barrier properties of chitosan based films and coatings were studied in relation to surface and structural properties. Water contact angles, material swelling, polymer degradation temperature, barrier properties (PO2, PCO2, WVP) and aroma diffusion coefficients were determined. The solvent nature and the presence of carvacrol influenced the surface and structural properties and then the barrier performance of activated chitosan films. Increasing RH from 0% to 100% led to a significant increase in material swelling. The plasticization effect of water was more pronounced at high humid environment, while at low RH the matrix plasticization was induced by carvacrol. The deposit of a thin chitosan layer on polyethylene decreased PO2 and PCO2 both in dry and humid conditions. The carvacrol release from the chitosan matrix was strongly influenced by RH. A temperature increase from 4 to 37°C also had an impact on carvacrol diffusivity but to a lesser extent than RH.

Protection of Active Aroma Compound against Moisture and Oxygen by Encapsulation in Biopolymeric Emulsion-Based Edible Films

Edible films made of iota-carrageenans display interesting advantages: good mechanical properties, stabilization of emulsions, and reduction of oxygen transfers. Moreover, the addition of lipids to iota-carrageenan-based films to form emulsified films decreases the transfer of water vapor and can be considered to encapsulate active molecules as flavors. The aim of this study was to better understand the influence of the composition and the structure of the carrageenan-based film matrices on its barrier properties and thus on its capacity to encapsulate and to protect active substances encapsulated. Granulometry, differential scanning calorimetry, and Fourier transform infrared spectroscopy characterizations of films with or without flavor and/or fat showed that the flavor compound modifies the film structure because of interactions with the iota-carrageenan chains. The study of the water vapor permeability (WVP), realized at 25 and 35 degrees C and for three relative humidity differentials (30-100%, 30-84%, 30-75%), showed that the flavor compound increases significantly the WVP, especially for the weaker gradients, but has no effect on the oxygen permeability. This study brings new understanding of the role of carrageenan as a film matrix and on its capacity to protect encapsulated flavors.

Temperature influence on moisture transfer through synthetic films

Abstract Water transfer through films was investigated as a function of the temperature, the physical state of water and the relative humidity (RH) difference. The films were two synthetic packagings: a hydrophobic one, the polyethylene, a hydrophilic one, the cellophane. Some phenomena which could occur at low temperatures were discussed, such as polymer structure change due to mechanical relaxation or network plasticisation and modification of the penetrant diffusion at its melting temperature. But it seems that the comparison of water permeabilities (WPs) with temperature, especially at subzero temperatures, requires the correction of their calculation with the difference of water chemical potential (Δ μ ) instead of the water vapour pressure difference (Δ p ). The predominant factor of the water transfer is the kinetic factor, i.e. the water diffusion; nevertheless, the thermodynamic parameter, i.e. the water sorption, linked to the physical state of water, affects the barrier efficiency of water-sensitive films inducing a water liquid permeability (WLP) higher than that of water vapour (WVP). For hydrophobic polymers, such as polyethylene, the water transfer depends only on the RH difference of both sides of the film.