Food Contact

Food Contact Science and Testing: What Are OML, SML and QM?

Little Pro on 2018-09-03 Views:  Update:2018-09-03

The migration of a hazardous substance into the food stuff is the main safety concern for food contact materials (FCMs). The compliance of FCMs  is often verified by migration testing. Suppliers of food contact materials need to demonstrate that their products comply with relevant overall migration limits (OML), specific migration limits (SML) and/or maximum permitted quantity (QM). In this article, we will give you an overview of what are OML, SML and QM and compare their differences.

Overall Migration Limit (OML)

The overall migration limit (OML) is the maximum permitted total amount of non-volatile substances that can migrate from a food packaging material or food container into food. The overall migration is determined by exposing the item to a chemical food simulant for a specified and appropriate length of time, after which the extracted residue is dried and weighed.

  • It measures the inertness of a food packaging material or article. 
  • It is usually expressed mg as per food contact surface area (mg/dm2)
  • For FCMs for infants and young children, it is expressed as mg per kg food (mg/kg).

Regulation (EU) No 10/2011 on Plastic Materials and Articles has set out OMLs for plastic food contact materials and articles.

  • For general plastic FCMs, the OML is 10 mg/dm2.
  • For FCMs for infants and young children, the OML is 60 mg/kg food.

Note: OML only measures the inertness of a FCM. It is not a safety limit.

Specific Migration Limit (SML) and SMLT

The specific migration limit (SML) is the maximum permitted quantity of a specific substance that can migrate from a food packaging material or food container into food. It is a safety limit derived from toxicological studies. Reliable analytical methods are needed to identify the presence of these substances in food (or food simulants).

  • It is usually expressed as mg/kg food.

The annex I of Regulation (EU) No 10/2011 on Plastic Materials and Articles has set out SMLs. If no SML is set, default limit 60 mg/kg food can be used for individual substances.

Sometimes, total specific migration limit (SMLT) can be set for a group of similar substances. Its unit is also mg/kg food.

Maximum Permitted Quantity (QM) and QMA

The QM is the maximum permitted quantity of a type or group of residual substance in a finished material or article. It is usually expressed as mg per kg food contact materials. We measure the level of the residual substane in food contact materials, not in food or food simulants. 

When expressed as mg per 6 dm2 of the surface in contact with foodstuffs, QM is also called QMA.

Comparison of OML, SML and QM

Type Unit How to Measure
OML
  • mg as per food contact surface area (mg/dm2)
  • mg per kg food(mg/kg) for FCMs for infants and children

The overall migration is determined by exposing a food contact material or article to a chemical food simulant for a specified and appropriate length of time, after which the extracted residue is dried and weighed.

It measures the total amount of all non-volatile substances that can migrate into food. 

SML
  • mg per kg food (mg/kg) for FCMs for infants and children
The specific migration is determined by exposing a food contact material or article to a chemical food simulant for a specified and appropriate length of time, after which the content of the specific substance in food or food simulant is determined by appropriate analytical methods. 
QM
  • mg per kg food contact material (mg/kg
The residual content of a specific substance in a food contact material or contact can be measured directly by using appropriate analytical methods.

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 Tags: Topics - Food ContactFood Contact Regulations

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