The number two within the triangular recycling symbol designates High-Density Polyethylene (HDPE). HDPE is widely recognized by regulatory bodies as one of the most chemically stable and safe options for direct food contact applications. Understanding why HDPE is trusted involves examining its chemical structure, physical properties, and the necessary precautions for its long-term reuse.
Recognizing High-Density Polyethylene
High-Density Polyethylene is a common plastic easily identified by its resin code, the number 2 inside the chasing arrows symbol, usually stamped on the bottom of a container. The polymer often presents as opaque or slightly translucent, giving it a milky-white appearance. Its molecular structure gives it a high strength-to-density ratio, resulting in a stiff and durable material. Common food items made from HDPE include milk jugs, juice bottles, butter tubs, and cereal box liners. While it is also used for non-food items, only virgin-grade HDPE that meets specific purity standards is approved for food contact.
The Chemical Stability of HDPE
The safety of HDPE for food contact is primarily due to its unique linear polymer structure. This arrangement results in strong intermolecular forces, making the plastic highly stable and resistant to chemical degradation. This structure creates a dense, non-porous material that prevents the migration of substances from the plastic into the food it contains. HDPE is considered non-leaching and biologically inert, meaning it does not react with a wide range of contents, including acidic or fatty foods. This chemical resistance is a primary reason it is approved for food contact by regulatory bodies such as the U.S. Food and Drug Administration (FDA). The presence of Bisphenol A (BPA) and phthalates is not an issue with pure HDPE, as these components are not used in its manufacture.
Consumer Guidelines for Safe Reuse
While HDPE is safe for food storage, consumers must follow certain guidelines when reusing containers due to its physical properties. The plastic has a relatively low melting point, softening around 120 to 130 degrees Celsius (248 to 266 degrees Fahrenheit), meaning HDPE containers should never be placed in a microwave, as high heat can degrade the polymer structure. Avoid putting these containers through the high-temperature cycles of a dishwasher, as repeated exposure to heat can compromise the container’s structural integrity. Scratches or cracks can harbor bacteria, making thorough cleaning difficult and unsanitary. Consumers must also refrain from reusing HDPE containers for food if they originally held non-food items like cleaning chemicals or motor oil; for safe, long-term reuse, containers should be gently cleaned with mild soap and water to limit surface damage and ensure proper sanitation.