Food contact barrier property

In addition to their water solubility, PVALs are appreciated for their good mechanical properties in the dry state, resistance to common solvents, barrier effect in dry atmospheres, possibility of food contact for suitable grades, biodegradability. 

In 2004, Treofan GmbH developed a metallised version of its PLA biodegradable film that reduces permeability aromas, oxygen and water. The metallised Biophan PLA film is said to be suitable for packaging fatty foods such as butter and cheese, as well as for confectionery, where the mirror-like finish adds a decorative feature to the barrier properties. The metallised film meets both EU and US, Food Drug Administration food contact requirements. 

Chem. Descrip. Paraffin wax CAS 8002-74-2 EINECS/ELINCS 232-315-6 Uses Water absorp. barrier in hardboard, paper sizing and paperboard applies., food-contact adhesives/paper Features Chem. stability to acids, alkalis, and inorg. salts Regulatory EDA21CER 175.105,176.170,176.180 approved Properties Aq. emulsion vise. < 1000 cps m.p. 120-130 F pH 6.5-7.5 anionic 49-51% solids... 

In food contact materials, polymer nanocomposites-based packaging materials are developed by the inclusion of nanoscale fillers resulting in clear improvement of food quality and extension of the shelf-life through minimizing microbial growth. They can serve not only as barriers to moisture, water vapour, gases and solutes, but also as carriers of some active substances. The enhancement of the polymer barrier properties is the most obvious application of nanocomposites in the food industry. 

PTFE is, for example, used to coat cookware intended for stovetop cooking and baking. Other PFCs, such as fluorotelomer and perfluoroalkylsulphonic acid derivatives (e.g., PFOSF), are or have been used to treat paper to improve its moisture and oil barrier properties. In particular, papers used in contact with high-fat content foods may be treated with fluorotelomer or perfluoroalkyl-sulphonyl-based paper additives/coatings to prevent oil stains or oil soak through the paper. Typically, these paper coatings/additives are phosphate esters or acrylic polymers containing polyfluoroalkyl functionality [12]. 

PLA could make a significant contribution to reducing the environmental problems associated with polymer waste. PLA can provide similar mechanical properties as conventional polymers, while leaving a lower environmental footprint [137, 138]. In addition, PLA has adequate impact resistance, good processability, and food contact acceptance. However, this desirable polymer has also disadvantages, such as poor thermal stability, brittleness, and lower gas and water vapor barrier properties. The permeability of currently available PLA is adequate for specific applications where gas and water vapor barriers are not needed, or when storage requirements are short. 

Slavutsky et al. (2014) prepared starch/cellulose nanocrystals (CNCs) films and their water barrier properties were studied. The measured film solubility, contact angle, and water sorption isotherm indicated that reinforced starch/CNC films have a lower affinity to water molecules than starch films. Permeability, dififusivity, and solubility coefficients indicated that the permeation process was controlled by the water diffusion and was dependent on the tortuous pathway formed by CNC incorporation. The decrease in surface hydrophilicity and the improvement in water vapor barrier properties with the addition of CNC showed that these nanocomposites present excellent potential as a new biomaterial for application in food packaging and conservation. 

Another approach to improve starch polymers properties is the use of nanotechnology. BIOP Biopolymer Technologies is developing starch-polyester with clay nanocomposites. Materials obtained were proven to fulfil European directives on food contact materials and have suitable mechanical and barrier properties [27]. 

Intercalation of thermoplastic starch with clay nanocomposites has been shown to improve modulus strength, thermal resistance, and enhance hardness [98,99], while the migration of additives has been shown to be at the level acceptable for food contact [ 100]. Elasticity of the films was however reduced though barrier properties are reported to be improved, without major change in the crystallinity of the polymers [101]. 

This is a very thin plastic film in the order of 10 microns and is commonly used for covering food items. It does not possess veiy high barrier properties and often used for covering the items for avoiding their direct contact with foreign substances for short durations especially for food items. 

FDA regulations permit use of up to 25% acrylic acid for copolymers of ethylene in direct food contact. The EAA flexible films have similar chemical resistance and barrier properties as LDPE. However, these have better strength, toughness, hot tack and adhesion than LDPE. As the content of acrylic acid increases, the ciystalhnity decreases and clarity increases. It is used in blister packaging and as an extmded tie layer between aluminum foil and other polymers. EAA films are also used in flexible packaging of meat, cheese, snack foods, skin packaging and in adhesive lamination. 

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