A leading north London kosher butcher has been investigated by Barnet Council after an anonymous complaint.

The council confirmed this week that it was talking to the Kosher Deli chain but refused to go into detail about the reasons.

However owner, Albert Ben Dahan, said he was working closely with the council to resolve the issue and revealed that the complaint was about the discovery of sulphur dioxide in a portion of minced chuck steak that the council had bought and had taken away for analysis.

“The amounts we are talking about are infinitesimally small and would not have any effect on anyone,” he said.

Agron Tali, a food scientist who works with Mr Ben Dahan, said that sodium sulphate can be used legally in the production of burgers and sausages and helps extend the shelf-life of such products by two to three days.

“Sodium sulphate keeps out certain bacteria. It also controls pathogenic bacteria such as salmonella.

“What was found was 220ml per kilo of sulphur dioxide, which is created when sodium sulphate comes into contact with oxygen in the meat, whereas the permitted legal level is 550ml per kilo in burgers and sausages.

“So one can see that it was way under what is allowed. We have gone through very carefully why this happened. We believe the explanation is that we make mince in our shops, to ensure that it is as fresh as possible.

“A batch of burgers was made on a mincer and it appears that a minute amount of sulphur dioxide may have been left on the machine after it was cleaned. The chuck steak was minced afterwards and picked up the small amount that was there. It is worth bearing in mind that sulphur dioxide also occurs in water and in the salt with which meat is koshered.”

Mr Ben Dahan added: “If we were putting in an additive, it would have been found in our minced chuck and minced steak. But this was only in the chuck mince. My factory and kitchens are inspected regularly by businesses with which we deal as well as the usual health checks that one must have.”

A spokesman for Barnet Council said: “This investigation has involved discussions with the owner and if, as a result there are any causes for concern, appropriate action will be taken.”