A critical comparison of four test methods for determining overall and specific migration from microwave susceptor packaging

Four approaches for testing for overall migration and specific chemical migration from microwave susceptors were evaluated. The methods used olive oil as a conventional liquid food simulant, a semisolid simulant of olive oil and water absorbed onto diatomaceous earth, Tenax(TM) as a dry simulant, and compositional analysis of the susceptor by ASTM methods. The different methods were tested on five susceptor types used for the packaging of pizza, potato chips (French fries), pasty, popcorn, and a curry. For the comparison, the susceptor materials were impregnated with model substances as migration markers covering a range of molecular weight, volatility and polarity. Levels of specific migration (SM) and overall migration (OM) were determined using the four test methods, which were then evaluated on the basis of their ease and reproducibility of use along with the agreement between specific migration levels into simulants compared with migration into foods. There were severe problems with olive oil as a conventional liquid simulant as it was absorbed by the susceptor and made SM and OM measurements difficult. Humidity conditioning the susceptor for OM was a further difficulty with olive oil. Oil absorption was also a problem using the semisolid simulant, with OM being untried using this approach. The ASTM methods were found to be time-consuming, although the results for SM were similar to those obtained for foods. Overall, however, using Tenax was the preferred method for migration testing of susceptors. It allowed easy measurement of both OM and SM, SM values were generally much higher than for foods, however, and a reduction factor would be required for control of regulated ingredients. For other substances, such as thermal degradation products, a threshold of regulation approach applied to the Tenax extract would be a simple and effective control measure.