Migration Boundary
Liquid food contact compliance requires EN 1186 Overall Migration testing to quantify the total mass of non-volatile substances transferred from a paper or board substrate into specific liquid food simulants under defined time and temperature conditions. Gravimetric analysis determines this mass transfer by measuring the residue left after the evaporation of the simulant, establishing whether the substrate remains within legal thresholds for packaging safety. The procedure stops applying once gaseous phase transfer or dry contact scenarios occur, because those situations fall under separate regulatory frameworks with distinct analytical parameters.
Gravimetric precision depends on constant mass drying protocols, requiring analytical balances capable of reading to one tenth of a milligram to detect minute residue shifts accurately. Testing laboratories select simulants corresponding to the intended end-use foodstuffs, meaning aqueous, acidic, and fatty simulants isolate different chemical fractions from the paper matrix. Water-based coatings and wet-strength resins undergo rigorous screening through this protocol to prevent unwanted taste transfer and regulatory non-compliance during commercial beverage packaging operations.
Extraction Limit
Regulatory compliance relies on a strict ceiling of ten milligrams of transferred constituents per square decimetre of contact surface, or sixty milligrams per kilogram of food simulant volume when calculating specific surface-to-volume ratios. Exceeding this mass limit triggers immediate rejection of the packaging grade, forcing converters to reformulate wet-end additives or replace synthetic sizing agents with approved alternatives. Hot-fill and retort applications accelerate molecular mobility within the cellulose matrix, demanding low-migration barrier dispersions applied via size press or curtain coater to maintain safe residue levels under thermal stress.
Extractive fractions typically consist of residual defoamers, plasticizers, and low molecular weight oligomers originating from recycled fibre furnish or virgin pulp bleaching chemicals. Analytical variability increases when testing recycled paperboard due to the complex mixture of unknown contaminant compounds present in mixed office waste streams, necessitating duplicate testing runs to verify baseline stability.
Simulant Protocol
Foodstuff polarity dictates the selection of aqueous, alcoholic, or synthetic fat simulants, each targeting specific solubility parameters inherent to the coating formulation. Ethanol solutions at ten percent concentration replicate hydrophilic beverages, whereas isooctane or modified olive oil serves as the standardized fatty food simulant for greasy bakery substrates. Contact duration and temperature parameters simulate worst-case distribution scenarios, ranging from chilled storage up to prolonged sterilisation cycles at elevated temperatures.
Migration kinetics follow diffusion principles, meaning higher temperatures exponentially increase the transfer rate of mobile chemicals across the fibre interface. Converting plants mitigate high migration results by applying functional barrier layers that physically block molecular diffusion before the finished carton reaches the packaging line.
