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Test gives clean bill of health for disposable take-away food containers and guidelines on proper use - CHOICE # 350

  • 2005.12.15

Eating from disposable plastic food containers is increasingly a way of life for both the rich and poor, young and old, these days. 

Apart from creating a colossal waste disposal problem, these food containers are also a cause of health concern, especially in the wake of recent reports from the mainland concerning toxicity of such utensils.

To assess food safety and suitability of using disposable containers, the Consumer Council in collaboration of the Food and Environmental Hygiene Department have conducted a joint test on the products available to the public in Hong Kong.

A market survey was conducted to obtain information about the use of disposable plastic food containers among the local food establishment in June-July and samples were collected from a diverse range of eateries, convenience or take-away food outlets and school lunch box suppliers in September this year.

It was found that the great majority of these disposable plastic food containers was made of expanded polystyrene (EPS), commonly called foam boxes, followed by polypropylene (PP). The few remainders were of polystyrene (PS), and polyethylene terephthalate (PET).

For food safety, the samples were put to tests, to detect the potential presence of heavy metals and residual styrene monomer (only for EPS and PS containers), the latter is a substance of possibly carcinogenic to humans according to the International Agency for Research on Cancer.

To determine the suitability of the use of the disposable containers, additional tests were conducted to examine the level of overall migration that might take place whilst in contact with different types of food under different conditions.

The test results showed that by and large, the samples tested were in compliance with food safety standards and should, therefore, pose no health risk in the normal usage of the products.

On residual styrene monomer, the level detected ranged from non-detectable to 0.047% (by weight), far below the 0.5% limit stipulated by the US Food and Drug Administration (FDA).

On heavy metals, all samples were found to fall within the safety level of the relevant GB Standards, the national standard of the mainland.

On overall migration, the US FDA standard permits a limit of 0.5 mg per square inch of food contact surface. Substances that might be migrated from the containers when in food contact include stabilizer, filler and plasticizer which are added in the production of the plastic material to improve the properties of the material.

The test was conducted in simulation of different types of food under different conditions as follows:

  • On test condition of 100℃ water and contact time 30 minutes (simulating in contact with 100℃ acidic and non-fatty food), all the samples were not detected with migrated substances.
  • Test condition of 65℃ heptane and contact time 2 hours (simulating in contact with 120℃ acidic and fatty food), one polystyrene (PS) food container was found to have a value of 0.81 mg per square inch of food contact, in excess of the 0.5 limit of the FDA standard.
  • Test condition of 49℃ heptane and contact time 30 minutes (simulating in contact with 100℃ acidic and fatty food), the same PS container was found to have a value of only 0.35 mg per square inch, in compliance of the FDA standard.

The test demonstrates that PS containers are safe for use provided that the food temperature does not exceed 100℃. In reality, the PS container concerned was not used for hot food but for hot dogs or similar food, and therefore, there is no food safety concern.

Consumers and food suppliers are advised to use disposable containers with good heat resistance property such as polypropylene containers to hold acidic and fatty food of temperature 120℃.

In addition, avoid putting hot food into plastic containers too early to reduce the possibility of physical deformity and migration of substances. Discard the food if the plastic container is observed to be deformed.

EPS food containers should not be used in microwave oven to reheat take-away food; microwave oven safe containers should be used instead. Do not reuse a disposable microwave safe plastic container in microwave oven because it may be designed to be used only once.

In the light of the test findings, the Food and Environmental Hygiene Department is to issue guidelines to the food trade on the use of disposable plastic containers.

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