The Consumer Council on Thursday urged manufacturers to ensure the quality of sesame products after its tests found a majority of samples contained contaminants.

The consumer watchdog tested 35 samples of sesame oil, powder and paste often found at markets, and found that 27 of them contained contaminants.

Among them, four samples were found with plasticisers exceeding the "action level" set by the Centre for Food Safety, one of them by up to 79 times.

"We know that plasticisers are mainly affecting the hormones in human beings, and also long-term excessive consumption of plasticisers may affect the development of the reproductive system of experimental animals and damage the health of organs such as liver and kidney," said Kyrus Siu, who chairs the council's publicity and community relations committee.

The council's chief executive, Gilly Wong, said traders should look into the manufacturing process to try to trace the source of the plasticisers.

"Because the manufacturing process covers different aspects, including how it's manufactured, what kind of container they are using, what kind of pipes they are using in the plants, and also how it's getting transferred and how it's stored. All the different points would affect or have the reason to cause the plasticisers," she said.

"We really advise the manufacturer to look into the manufacturing process to find out the exact answer. They have to go through step by step, every checkpoint, to find out exactly in what area (things) went wrong."

Separately, the watchdog tested 30 Chinese sausage samples and found that six of them have colouring substances banned in Hong Kong and Europe.

One product by the Kam Wong Medicine Company in Mong Kok was detected with food colour “Red 2G” which could be carcinogenic.

Wong said consumers can soak the sausages in water to minimise the impact.

"If you wash it in advance and also chop off the string at the head of tidying up the sausage, it will also help you to reduce the risk," she said.