Migration and Food-Package Interactions PDF

Migration and food-package interactions Physical, chemical or biological interactions often occur at the food-package interface. – Physical: movement of chemical compounds across the food- package interface. – Chemical: corrosion of a metal container caused by contact with a food...

Migration and food-package interactions Physical, chemical or biological interactions often occur at the food-package interface. – Physical: movement of chemical compounds across the food- package interface. – Chemical: corrosion of a metal container caused by contact with a food product. – Biological: food spoilage due to microbial contamination by the package. Concerns: movements of harmful chemical compounds from the package to the food, or in the opposite direction. a) Macroscopic scale: movement of relatively large fragments during processes. b) Submicroscopic scale: movement of submicroscopic compounds by molecular diffusion.  Migration and food-package interactions Migration: submicroscopic food-package interaction involving the movement of chemical compounds in the direction from the package to the food. – The movement is controlled by molecular diffusion. – Particular concern: migrations from plastics  related to consumer protection and regulatory compliance. Scalping: migration of chemical compounds from food to package (reverse migration). – E.g. flavor scalping: – food contact layer of the package is made of plastics – loss of desirable food flavors in the food.  Migration and food-package interactions Other important food-package interactions: – Food contamination  may cause corrosion on surfaces of metal, glass and ceramic. – Desirable and intentional migration of active compounds, e.g. active packaging: antimicrobials or antioxidants  incorporated specially into the package  allow these active compounds to be released slowly from the package to enhance safety and quality of the food.  Migration process & potential migrants Potential migrants in plastics intended to be in contact with food: – Additives E.g. esters, organic salts, amines, etc. Small molecules (low molecular mass) compared to the hosting medium (very high molecular mass) Different chemical nature from the inert medium in which they are dispersed high mobility is expected in plastics. – Residuals E.g. monomers, catalysts, solvents, adhesives Left from the process of production or converting Different chemical nature from the inert medium in which they are dispersed  high mobility in plastics. – Neo-forming molecules Decomposition products. E.g. acetaldehyde & oligomers in PET Produced from the reactions that may occur during the processing or ageing of plastic materials.  Migration process Non-migrating system – Negligible migration for high MW polymer, some inorganic residues, or pigments. – Zero assumption may be changed depends on non-detectable limits in analytical techniques or regulatory specifications. Volatile system – Does NOT require contact between the packaging and the food, even though it may be affected by the contact. – Applies to dry solid food with poor direct contact with the package. – Migration to the food is limited to volatile compounds which have relatively high vapor pressures at room temperature. – The migration is usually controlled by the diffusion in packaging material, NOT by characteristics of food phase. – The volatile compounds in the packaging wall may also be evaporated into outside environment without causing migration toward food.  Migration in the case of poor food-package contact –Steps: Diffusion of migrant in package wall toward the food-package interface. Desorption of migrant at food-package interface. Adsorption onto food.  Migration process Leaching system – Requires contact between the packaging and food – mostly liquid or moist solid foods Mechanisme: a. the migrant has high diffusion coefficient in the plastic  easily dissolved into the contacting food phase. b. the migrant is of low diffusion in the plastic at the initial contact with food but gain high diffusion coefficient after liquid food component has been adsorbed and diffused into the film  swelling of plastic material  accelerates diffusion of migrant.  Migration in the case of good food-package contact Steps: Diffusion of migrant in package wall toward food-package interface. The slowest or rate-determining step of migration In dual-interactive mode, concurrent penetration of solvent or food ingredient may change the package wall structure to swell  increasing mobility of migrant. Dissolution of migrant at food-package interface. Depends on the affinity of migrant to the package phase and food phase. Dispersion or diffusion of migrant into food. The migrant will then disperse into liquid foods or diffuse into solid foods.  Migration process Diffusional mobility of potential migrants in the package (typically along the thickness of the package walls) depends on: – Temperature – Time – Molecular mass – Chemical affinity with the plastic in which they are present Motion of the potential migrants is actually very slow. – Several days are normally needed for the migrants to go through a few micrometers of plastic thickness. – Fick’s First Law: J = -Dp (dC / dx) J is diffusion flux (mg m-2 s-1), Dp is diffusion coefficient of migrant in packaging material or diffusivity (m2 s-1), C is migrant concentration (mg m-3) and x is the distance in the package layer. Potential for migration is related to the characteristics of the molecules, of the contact phase (i.e. the food or beverage inside the package), and of contact condition. – Volatility of the potential migrant can affect direction and degree of migration. – Ability of the contact phase to dissolve immediately the migrated substance can influence the rate of migration. – The agitation or the turbulence induced by transportation or other causes can accelerate and promote migration.  Migration issues in food packaging The type of food contact material, the time of contact, and the temperature of contact  deeply affect the possible migration. Any substances that migrates from the packaging into the food is of concern  could be harmful to the consumer. – Even if the migrating substance is not potentially harmful, it could have an adverse effect on the flavor and acceptability of the food  should be avoided. – Important: to prevent the packaged food from possible contamination from the packaging material used for protection function.  Migration issues in food packaging Chemicals from plastics – Plastics: most prone to migration, due to: – Heterogenous nature (formulated with different additives according to the performance required). – Manufacturing process (which can lead to the presence of residuals and also to the production of new-forming substances). – Synthetic origin. – Example of concern: VCM (vinyl chloride monomer) from PVC  potent carcinogen substance. Plasticizers (additives used to improve flexibility). E.g: phthalate plasticizers are not chemically bound to PVC, they can easily leach and evaporate into food or the atmosphere- asthma and allergies Primary aromatic amines (PAA) - carcinogenic  neo-forming (produced from the reaction between isocyanate and food moisture; isocyanate and polyols are the starting substances for polyurethane adhesive, largely used in laminate manufacturing; if not enough time is awaited for completing the cross linking of the adhesive, the residue within the structure may react with water  synthesis of PAA  can migrate into foods, occasionally found in moist food (e.g. mozarella cheese) packed in plastic laminate structure.  Migration issues in food packaging Recycled plastics – Post consumer recycled (PCR) plastics may contain chemical contaminants originating from : their previous use contact with other wastes, or due to technique used for recycling. – PCR plastics have to be separated from the food by an effective barrier made from a material designed to protect the food (effective barrier)  not a total , absolute barrier, but only a functional barrier (FB): selectively stops the transfer of specific compounds. – FB must ensure the migration of authorized substances below the limit of specific migration (SML) and/or reduce the migration of nonauthorized substances to a ‘nondetectable’ or ‘acceptable’ level, e.g. 10 ppb in Europe.  Only metals, glass and PET are currently approved for use as functional barriers (EU) A functional barrier prevents all types of chemicals that can be found in recycled paper, recycled plastics and printing inks, for example, from transferring to products such as packaged foods. These barriers can be used on paper and board made from recycled fibres containing chemical residues from sources including printing inks.  Migration issues in food packaging Microwave susceptor – Multilayer structures used as packaging material, as part of a package, or as a plate or a baking-pan, in order to add crispness and browning to microwaved foods. convert microwave E into heat and provide a localized heating with very high T. E.g. very thin layer of aluminum in a metallized plastic film laminated to paper, board, or others. Most applications: in PET or oriented polypropylene (OPP) film. – Very high temperature (can be up to 2000C in less than 1 minute): possible diffusion phenomena. The plastic film may deteriorate  formation of cracks  food components rapidly migrate into the plastic and the underlying layers  migration of adhesive compounds from the plastic film to food.  Other examples of problems in food packaging Paper & board Taint problems. eg: paper sacks contained a number of chlorophenols – produce chloranisoles (fungal methylation) – responsible for strong musty taints Can Migration of can lacquers into canned foods Migration of bisphenol-A from cans into drink after heating of more than 105oC  Flavor scalping and sorption Scalping of flavor occurs commonly by the ability of plastic polymers to dissolve many low molecular weight substances present in foods and beverages. Sorption: mostly limited to the surface of the material (adsorption) or the one that penetrates through the thickness of the material to different extents and by different mechanisms (absorption). The effects of scalping are generally undesirable because it can reduce or alter the flavor of a packed food. The effects of sorption phenomena exceed the sensory aspects and concern both the package and the product. – Sorption of limonene and other aroma compounds from fruit juices on LDPE (actually very prone to sorption), which is frequently used for contact with flavored beverages. Factors affecting sorption phenomena: – the polymer characteristics: morphology, polarity, chemical structure. – the sorbate: concentration, polarity, presence of a co-migrant. – the environment: temperature, relative humidity, geometry.  Flavor scalping and sorption The effects of sorption phenomena at the interface of food/packaging Effects on the food Effects on the package – Increase of permeability – Loss of vitamins (mainly the (mainly gas and aroma oil soluble). permeability). – Loss/change of the taste. – Decrease of mechanical properties. – Loss/change of the flavor. – Stress cracking – Change of the color. occurrences. – Reduction of natural – Loss of adhesion in antioxidant protection. laminated structures. – Decrease of seal strength. – Shelf life reduction (as a – Corrosion of laminated foil consequence of all those (for the sorption of acid previous effects). substances).  Sensory tainting Any material or article intended to come into contact either directly or indirectly with foodstuffs, must be stable enough not to transfer substances which could bring about deterioration in the organoleptic properties of the food  tainting phenomenon. Taint: a taste or an odor foreign to the product imparted to food through external sources. It’s different from off-flavors. – Taint: unwanted odors or flavors imparted to food through external sources. – Off-flavors: consequences of internal deteriorative changes occurring in foods or beverages.  Sensory tainting Compounds in flexible packaging materials able to taint the packed foods: – Inks used for printing. – Adhesives and solvents used in composite structure manufacturing. – Coating and varnishes applied on the contact surface.  All which also comprise of residual monomers (e.g. styrene), plastic additives, and decomposition or reaction products (acetaldehyde in PET, or oxidation products in polyolefins). Very low thresholds of sensorial perception. They often present in packages and migrate in foods at extremely low concentration (ppm or ppb, or even ppt). Eg: migration of styrene (hydrophobic monomer) partially dependent on the lipid content of the food. – sensory assessment detected a styrene taint in chocolate products.  Regulations All packaging materials must be safe from the possible migration of undesirable packaging constituents into the food  inertness of food contact materials. Positive list: contains all the approved components and ingredients for food contact, together with possible concentration limits and exclusions  costly, but ensures maximum level of safety. Negative list: covers the materials and the substances which are prohibited for their toxicity or dangerousness  generally short and ensures the safety less than a positive list.  Regulations OML (overall migration limit): a limit to the leaking/ migration from package (in ppm or mg.dm-2)  accepted widely, but the absolute levels are sometimes different with countries – ppm: Maximum amount that can migrate in the food mass – mg dm-2:The mass migrated from the package unit’s surface Specific migration limit (SML): a limit to the migrated amount of a specific substances QM (maximum quantity permitted): limit on the residual concentration of some substances in the finished article.  Migration testing 2 approaches in studying migration (to investigate rate and/or amount of a specific diffusion phenomenon from package to food): 1. Migration testing (simulation). 2. Predictive migration (estimation based on mathematical model). Migration testing: – Step 1: exposure of the package (or its representative sample) to the contact with food (or more often with an effective simulant). Important to control the temperature and the modalities of the contact. Chemical nature of the simulant, surface area and ratio of simulant volume/migrating surface. Test condition should generally be the realistic reproduction of possible interaction. – Step 2: quantification and identification of migrated substance Overall migration (OM) show inertness and stability of package or packaging materials, but it has nothing to deal with the danger of food/package interaction  easy to test with simulation test. SM: can be estimated by a predictive model.  Migration testing – food simulants Liquid or solid substances, having a simple and known composition, able to emulate the extraction capacity and solubility of foodstuffs  easier and more reliable migration tests. – Aqueous: distilled water. – Acidic: 3% (m/v) acetic acid in water. – Alcoholic: ethanol in water (8-50% v/v). – Fatty: olive oil, sunflower oil, corn oil, synthetic mixture of triglycerides. – Solid: adsorbent polymer (polyphenylene oxide, Tenax®), charcoal, milk chocolate. – Solvent: heptane, iso-octane, ethanol, ethanol-water  Migration testing – analytical techniques Gravimetric test overall migration (OM) – After the evaporation (for volatile simulant) or the removal of the simulant (for oil), the dry residue of the sample material after the contact is weighed to determine, by difference, the amount of solid substances migrated  OM (overall migration) Alternatives: – Measurement of optical density of the liquid simulant in the near UV region. – Organic extractable matters in distilled water are measured by titration with KMnO4 solution. – Sensorial analysis: an olfactory or gustative test performed on liquid or solid simulant Modern & advanced analytical techniques, e.g. FT-IR, GC- MS, LC-MS  SM (specific migration)