It was a cloudy Thursday afternoon. Because the pork provided by the cafeteria was inedible, several students decided to eat their own food. One student put his chicken nuggets into a PRISMS bowl and into the microwave. He set the heating time for three minutes and walked away. All of a sudden, someone shouted, “whose bowl is this!” The student hurried to the microwave and discovered to his surprise that the bowl had cracked, with one piece peeled off at the side. The surface of the broken piece was very rough.
In order to ensure the health of PRISMS students, *a distinguished group of scientists came to PRISMS and conducted a thorough investigation into whether the tableware at PRISMS is safe.
The chemicals commonly used in PRISMS tableware are styrene acrylonitrile resin (SAN) plastic for cups (the new opaque ones) and melamine for plates and bowls. SAN is a copolymer plastic composed of carbon, hydrogen, and nitrogen. It is transparent, durable, rigid, and chemically resistant to contaminants. Melamine, however, has been notorious in China for the protein adulteration incidents in 2008, when it was added to milk powder to raise the nitrogen level, a common indicator of protein content. Milk powder overloaded with melamine has been proven to harm the health of infants. Both SAN plastic and melamine are used widely in tableware for they rigidity and durability. Are they actually safe?
All materials have higher or lower maximum temperature for use. If the temperature exceeds this limit, the material may change its chemical and physical properties or even become toxic. For SAN plastic, maximum temperature according to Endura Plastics Inc. is 200 ˚F (93.3 ˚C) for short duration, and 140 ˚F (60 ˚C) for long term. However, Endura’s website does not specify how was the value measured or estimated. According to AZO materials, the melting point of SAN plastic is 220 ˚C to 270 ˚C. Once the temperature exceeds this range, the beautiful plastic cups in our school will melt.
People have different concerns about melamine. The most common concern is: if melamine is toxic when added into milk powder in excessive amounts, will melamine tableware get into our food and drink and harm our health? According to U.S. Food & Drug Administration (FDA), when it is for actual-use conditions (e.g. cold orange juice in the tableware for 15 minutes), the migration is 250 times lower than the level of melamine that the FDA has concluded to be acceptable. However, when highly acidic foods are heated to 160 ˚C (71 ˚C), the migration can increase, which increases the risk. So food and drink should not be heated in melamine-based dinnerware in microwave ovens.
Hot chocolate made by cafeteria microwave
From the data provided about SAN plastic and melamine, tableware made using these two chemicals is safe for common use. However, for our safety, heating in a microwave oven should be avoided for food using melamine tableware, especially for acidic foods. Students should also be careful heating the SAN plastic cups. So try to be more cautious when making hot chocolate.
*Disclaimer: No scientists actually came to PRISMS to examine our tableware. However, the story was the experience of one student at PRISMS and a thorough investigation into the safety of our tableware is ongoing.