Stability of aseptically packaged food as a function of oxidation initiated by a polymer contact surface
In this study, low density polyethylene (LDPE) and polyethylene terephalate (PETE) resin beads were ground to a coarse powder and exposed to sterilization treatments applied to the food contact surface of packaging materials used in aseptically processed and packaged food. Electron paranlagnetic resonance (EPR) analyzed free radical (-CH2CHCH=CHCHz-) production on the surface of LDPE exposed to heat (107°C) and treatments of heat (107°C) + 30% hydrogen peroxide solution (H20 2). As the temperature was raised from 100° to 200°C, peak intensity of carbon radicals produced gradually increased. The sensitivity of EPR prevented detection of free radicals on LDPE, exposed to H20 2 treatment, due to residual peroxide and H20 condensation on the surface of LDPE. D-limonene was placed in 12ml sealed glass vials containing a sodium citrate buffer solution (pH=3.7), under atmospheric O₂ (21%) conditions. Oxidation of d-limonene, placed in intimate contact with untreated, HzOz treated, and ultraviolet (VV) light (650mW/cm2) treated LDPE for 15 weeks, was measured to determine the capacity of an oxidized polymer to initiate autoxidation. The oxidation of d-limonene in vials containing no polymer was also measured. Production of carvone and carveol were used as an index for oxidation. No polymer and UV treated samples showed significantly (P<0.05) higher levels of calVone and calVeol than samples containing untreated and HzOz treated LDPE. Samples containing no polymer oxidized d-limonene at the highest rate, but not significantly faster than solutions containing UV treated LDPE. Accumulation of carvone and carveol was zero order.