Expensive manuka honey sold as "pure" in Hong Kong has been tested and found to have rogue ingredients including sugar or sugar syrup, the Hong Kong Consumer Council says.
But the New Zealand Bee Products Standards Council says while the result was shocking, testing of manuka honey had produced high levels of false positives to sugar content.
Chairman Dr Jim Edwards said they were aware of the Hong Kong report but did not know how the honey was tested or whether it was checked using a newly created and more reliable test.
"We have been aware of the need to resolve the testing problems," he said.
''We are watching with interests - our reputation is important."
The Hong Kong Government-funded Consumer Council says that when people buy natural pure honey the last thing they expect is syrup.
"This is the shocking revelation of a recent Consumer Council test on 55 samples of honey," it says in a media statement.
"The results indicated that as many as 14 samples, or up to one-quarter of all samples, were adulterated with sugars."
The South China Morning Post published a list of the offending samples and all but one of the manuka brands were from New Zealand.
The Consumer Council says the problem was "more prevalent" with the more expensive manuka honey samples.
The international CODEX Standard for honey stipulates that honey should not have added to it any food ingredient, including food additives, nor should any other additions be made other than honey.
It should be natural and pure.
The Hong Kong Council has referred the findings on sugars-adulteration to the Customs and Excise Department for consideration whether the Trade Descriptions Ordinance has been breached.
Out of the 14 sugars-adulterated samples, 12 claimed they were natural or pure honey and among them seven claimed to be 100% natural or 100% pure.
"While it is not harmful to health, it should not be there in the first place," the council said.
New Zealand manuka beekeepers have been aware for years that their honey was different to others, and something in it made the standard sugar test inaccurate.
A GNS scientist Karyne Rogers has been commissioned by the Bee Council to investigate a 30% false-positive rate in the testing for sugar.
A new test introduced two months ago has dropped this to 6%.
Dr Edwards said the problem seemed to occur with the need of beekeepers to feed their bees during winter. They gave bees a kind of cane sugar known as C4 and bees stored the sugar in the hives to carry them through winter.
"We are finding now that the sugar that is not consumed, we can still detect it later on," Dr Edwards said.
The standard test for detecting added sugar worked well on other honeys, but not with manuka, he said. Scientists did not know why because manuka was an "evolving science".
Sugar was not added to honey itself.
"We ourselves consume cane sugar, so it is not a safety issue but it is a quality issue," he said.
The Standards Council says there is a need to understand the real physiology of the plants and their metabolism. There is a poor understanding of how native plants recycle sugar via bees.
Rogers' analysis of organic samples compared to normal commercial beekeeping samples confirmed that sugar-feeding was an issue. Testing of clover samples were clear while sugar problems were being detected in manuka honey.
The South China Morning Post said the studies had found sugar in the most expensive honey, the 250g Catalo New Zealand Active UMF 10 Manuka Honey, which sells for HK$378 (NZ$62) a jar.
The council was unable to provide specific figures on the amount of sugar in each product as it was a "very small quantity", making it "hard to quantify", council chairman Professor Michael King-man Hui told the Post.
The Hong Kong Consumer Council said that in the case of Catalo it was uncertain whether the contamination was deliberate or occurred during pollination.
"One possibility is when the bees are looking for . . . nectar from the flower, they get it from other sources including syrups and that's why it becomes a mixture in the source of honey," Hui said.
"The other possibility is the manufacturing process. Some kinds of syrups or sugars are being added."
Catalo nutritionist Jase Tsoi told the Post the company disputed the council's method of laboratory testing.
"We are sceptical about the sugar test method used for manuka honey," he said.
"The method they used is an old method by which a high percentage of high quality manuka honey would fail. In comparison, honey with lower quality usually passed the test."
And for the first time, the council analysed the plant species of pollen in the honey samples to determine the geographical origin of the honey. Discrepancies between the origin as analysed and the origin on the label or the product description was found in seven of the samples.
A sample labelled as "Made in Switzerland" was assessed to have its honey originating in China.
In another case, the word Korea in Chinese appeared in the product description but again the honey was assessed to have come from China.