Fall 2007 Newsletter
Concerns Over Microwaveable Food Safey
Food microwaved in plastic containers is a convenient choice for busy families. Yet we worry about potential contamination when plastic meets the high heat of the microwave oven. Here’s what happened when Chemir investigated the interaction between frozen dinners and “in the bag” microwave cooking.The Problem: Determine if packaging is contaminating food during microwave cooking
The first step was to determine the chemical make-up of the plastic packaging.
The plastic, or polymer, packaging samples were cryoground into a fine powder and then allowed to soak in a solvent in order to swell the polymer, but not dissolve it. The solution was then analyzed by GC/MS to help identify volatile or semi-volatile additives and also by LC/MS to determine the non-volatile species or higher molecular weight additives.
Hot stuff
A microwave oven heats by radiating the food at a frequency that rotates the water molecules. They are known for their inability to heat foods evenly and thus local “hot spots” can be present. The heated regions in contact with the plastic can generate ideal conditions for the migration of plastics additives and residual free monomers.
Let’s cook
Once the analysis of the packaging was complete, samples of food were prepared according to the microwave instructions. We also prepared a food sample in a glass dish as a control sample.
Were there additives in the food?
After cooking, the food was analyzed by extraction methods using multiple solvents of different polarities. The food samples were mixed with the solvents on an orbital shaker to facilitate maximum extraction. The solvent was then separated from the food material by filtration, dried with sodium sulfate, and then concentrated to increase the level of detection.
Next, the concentrated extracts were analyzed by chromatography. Quantitation of additives was achieved by analyzing standards at known concentrations alongside the food extracts. Concentrations of additives were then back-calculated to the amount of food in the package or to a serving size. Spike recovery studies were also performed in order to evaluate the effectiveness of the extraction methodology.
What we found
Two components from the packaging were found to migrate into the food tested. One serves as a flame retardant and the second as a plasticizer. The findings were communicated upon confirmation and with our help, the client has found a new packaging source that did not exhibit leaching.