ANSES: Reheating food packaging at exceedingly high temperatures increases the risk of substance migration

By Jenny Eagle

- Last updated on GMT

Related tags Microwave oven

A study on food packaging that can be heated in conventional ovens, microwaves or by steam has found while the migration of substances from the packaging to the food is generally low and below the regulatory values, it can increase significantly in the case of non-compliance with instructions for reheating.

The study was carried out by the French Agency for Food, Environmental and Occupational Health & Safety Society (ANSES) and the French Department of Information, Communication and Dialogue in response to changing dietary behaviour and consumption patterns.

Guidelines to advise consumers

To limit the risks of migration, ANSES has released guidelines to advise consumers to follow the manufacturers’ recommendations (degree and duration of cooking) indicated on food packaging.

Judith Nadjar, ANSES, said it also recommends avoiding the use of damaged packaging or packaging showing signs of wear.

As regards acidic foods (tomatoes, recipes using lemon juice, etc.), the Agency reiterates that consumers are strongly advised not to store or reheat such foods in aluminium foil, because the acidity increases the migration of aluminium into the food​,” she said.

In partnership with the French National Consumer Institute, several studies were carried out on different types of packaging (food bags for use in conventional or microwave ovens, bags for steaming or microwave ovens, and trays).

Polypropylene polymer most often used

In the samples studied, regardless of the type of packaged food, polypropylene was found to be the polymer most often used.

In the framework of the study concerning polypropylene food trays designed to undergo cooking in conventional or microwave ovens, the tests conducted under three conditions (ambient temperature, heating in the microwave following the manufacturer’s recommendations, and extreme heating) revealed the presence of POSHs (which can potentially be used as lubricants) in several samples kept at ambient temperature.

The level of POSH increased during reheating, and particularly in the case of extreme reheating (higher temperatures and for extended periods).

According to ANSES, its research and development partnership agreement with the French National Consumer Institute, puts responsibility for the safety of the processes used on the manufacturer, and requires specific instructions for safe and appropriate use be displayed on food containers.

To date, however, little data has been published in the scientific literature on the impact of different reheating practices on exposure of consumers to substances present in packaging materials. 

To make the best use of a microwave oven, ANSES makes the following recommendations:

  • Always check before use that the kitchenware is compatible with use in a microwave oven (this should be indicated by the manufacturer) and in good condition.
  • Do not keep single-use packaging for use as containers for microwaving food (e.g. do not reuse a food tray).
  • Give preference to long reheating times but at low power (e.g. two minutes at 650W is preferable to 50 seconds at 1270W), especially if no specific instructions can be found on a food's packaging.
  • Avoid the use of microwave ovens for reheating infants' feeding bottles: the distribution of temperatures obtained within the food could potentially cause burns to the child.

FoodProductionDaily is organising a one hour debate with four guest speakers on Food Packaging Migration​ today (March 13).

Migration of chemicals from packaging materials is a major concern for manufacturers, suppliers and the regulatory bodies responsible for consumer safety and health.

The extent to which a substance migrates depends on the chemical, the makeup of the material(s) from which it could be released and the food with which it comes into contact. Join us at 4pm CET to hear what our panel of experts have to say on the topic by registering here​ .

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