Residues of Quarternary Ammonium Compounds (QAC) in Fresh Fruit and Vegetables – Origins and Findings

Ein Bericht aus unserem Laboralltag

Marc Wieland, Anne Wolheim, Dr. Eberhard Schüle, Ellen Scherbaum

 

Summary

Residues of the quarternary ammonium compounds  didecyldimethyl-ammonium chloride (DDAC) and benzalkonium chloride (BAC) were detected in a wide variety of fruit and vegetable samples, the overwhelming majority of which were in excess of the general maximum residue level (MRL) of 0.01 mg/kg. Not only conventionally produced products, but also those from organic cultivation were affected. The residues can be caused either by the application of QAC-containing disinfectants in food processing procedures such as washing and packaging, or via the usage of plant strengtheners that contain these substances illegally. According to the German Federal Institute for Risk Assessment, an acute and chronic health risk is not likely, based on current DDAC residue findings.

 

Introduction

Quarternary ammonium compounds (QAC) are surface-active substances containing a quarternary cationic nitrogen atom and carbon chains (alkyl side chains) of various lengths.

 

Illustration 1: Structure of QAC.

Illustration 1: Structure of QAC.

 

QACs build up in the cell membranes of living organisms and can impair and damage their functions. As a result of these properties QACs are utilized as biocides, pesticides, disinfectants and as additives for technical applications. Furthermore, they are used as ingredients in human and animal medications, as well as in cosmetics.

 

Legal Aspects

Some QACs, such as didecyldimethylammonium chloride (DDAC) und benzalkonium chloride (BAC) were evaluated as pesticidal agents in Regulation (EC) No. 1112/2002. As a result of Decision 2004/129/EG, the majority of QACs were not included in Annex I of Directive 91/414/EWG, which has been rescinded and replaced in the meantime. As a consequence, QACs are not authorized for use in pesticides within the European Union. Only didecyldimethylammonium chloride (DDAC) is authorized for general use as a pesticidal agent, in accordance with Regulation (EC) No. 1107/2009. In some European member states, the use of QACs is authorized.

 

Since no specific maximum residue limits (MRLs) for QAC have been established under Regulation (EC) NO 396/2005, the generally applicable MRL of 0.01 mg/kg, in accordance with Article 18, Paragraph 1b of Regulation (EC) No. 396/2005 is valid for QAC residues in plant- and animal-based products listed in Annex I of this regulation. Whether the residues stem from the application of a biocide or a pesticide is immaterial.

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Analyses

A short description of the analytical methods developed by CVUA Stuttgart can be downloaded under the following link from the website of the European Reference Laboratory (EURL) for Single Residue Methods.

 

 

http://www.crl-pesticides.eu/docs/public/tmplt_article.asp?LabID=200&CntID=670&Lang=EN

 

Results

A total of 333 samples of fresh fruit and vegetables have been analyzed for QAC residues since May, 2012. Nine of the 159 samples of fresh fruit (5.7 %) were found to contain residues of QAC, of which seven samples exceeded the general MRL of 0.01 mg/kg (4.4 %). The highest detected quantity of residue amounted to 0.16 mg/kg DDAC in a banana sample. Six of the 174 samples of fresh vegetables (3.5 %) also contained residues of QAC, all of
which exceeded the accepted MRL of 0.01 mg/kg.

 

Illustrations 2 and 3: QAC Residues in All Samples and in Distinctive Product Groups.

Illustrations 2 and 3: QAC Residues in All Samples and in Distinctive Product Groups.

 

The highest amount of residues detected in fresh vegetables was 0.92 mg/kg DDAC in a sample of parsley. In addition, one out of a total of 11 analyzed samples of cultured mushrooms (champignons, oyster mushrooms and shiitake mushrooms) contained DDAC residues in excess of the MRL of 0.01 mg/kg. Residues in quantities above the legal MRL were mostly noted for the substance DDAC (11 samples); however, there were also exceedances of the MRL for the substance benzalkonium chloride (BAC) noted in three samples.

 

Illustrations 4 and 5: Number of Samples With and Without QAC Residues.

Illustrations 4 and 5: Number of Samples With and Without QAC Residues.

 

Fruit and vegetables from both conventional and organic cultivation were affected by positive findings and exceedances of the MRL. Four out of 46 organic samples contained DDAC residues (2 bananas, 1 rucola and 1 parsley). Residues of QAC were detected in various types of fruit and vegetables with widely ranging countries of origin.

 

Illustration 6: Number of positive samples by country of origin with number of samples > MRL.

Illustration 6: Number of positive samples by country of origin with number of samples > MRL.

 

Conclusion

Compounds containing QAC seem, therefore, to be used on a wider basis. One source of the QAC residues could be the application of biocides in the procedures used in food processing such as washing and packaging.  A further point of entry seems to be the use of plant strengthers.  For this reason, the preparation "Vi-Care" was recently removed from the official list of authorized plant strengtheners by the German Federal Office of Consumer Protection and Food Safety (BVL). It may no longer be distributed on the German market.  Furthermore, the preparation Wuxal Aminoplant, which contains the substance BAC, was also eliminated from list of authorized plant strengtheners by the BVL last week.

 

Artikel erstmals erschienen am 15.07.2014