A scientific study could fan the embers of a smouldering New Zealand versus Australia debate for the right to use the mānuka honey name.
Honey producers lost their latest battle in May against Aussie beekeepers to trademark mānuka after a ruling by the Intellectual Property Office of New Zealand.
But the debate continues to roll on, Kiwi producers arguing honey from nectar found in the mānuka species, Leptospermum scoparium, in New Zealand is very different from honey from the nectar of the diverse species of Leptospermum in Australia.
A lot is at stake as mānuka honey is prized for its antibacterial properties, which improve wound healing, and its antiviral, anti-inflammatory and antioxidant qualities, which it gets from an active ingredient called methylglyoxal (MGO) and possibly other components.
As any supermarket shopper can vouch, mānuka honey doesn’t come cheap.
Public awareness of this antibacterial activity, and its MGO content, has greatly increased demand.
Sometimes it’s worth more than double what high-grade honey from other nectar sources fetches and much more than this if it’s exported.
This explains the tussle for the right to use the mānuka label and, separately, the rise of unscrupulous producers fraudulently passing off cheaper honey as mānuka honey.
Now a study shedding new light on the chemical makeup of mānuka honey from both countries could reignite claims and counter-claims.
AgResearch Lincoln senior scientist Dr Alastair Ross and Dr Terry Braggins of Analytica Laboratories have analysed mānuka-labelled honey samples with advanced laser-assisted rapid evaporative ionisation mass spectrometry (REIMS) technology.
This tool hasn’t been used a lot for honey analysis before.
There’s now strong evidence to suggest the geographical origin of Leptospermum scoparium honey, commonly referred to as mānuka honey, has its own distinct molecular composition fingerprint.
Each nation’s samples are believed to have botanical and environmental factors unique to the regions they came from, which influence the honey’s composition.
Dr Ross said they found they could easily distinguish between the nations’ mānuka honey.
"While it’s a legal question about what can be called mānuka and what’s not, from a scientific perspective we were really surprised to find that Australia mānuka-labelled honey is very different to New Zealand mānuka honey, even though they are supposed to come from broadly the same plant."
Honey was more complex than people gave it credit for, he said.
He preferred to remain outside the debate and stick to the scientific results, Dr Ross said.
"Irrespective of whether the Australians call it mānuka honey or whatever, it does suggest that what we’re selling is different to what they’re selling. Stepping aside from whether they call it mānuka or not, this is suggesting that what we are selling and what they are selling is not the same. There may be a myriad of factors there, so it’s not just the fact our mānuka honey is coming from Leptospermum scoparium, whereas theirs could be coming from any one of your 80 different species of Leptospermum. There’s also how the honey’s processed, handled and everything like that."
Dr Braggins collected honey samples over a couple of seasons and while seasonal effects could be seen, the scientists could still tell the difference between an Australian and a New Zealand honey.
Dr Ross said that showed there was consistently a difference between the two.
"It’s really up to people within the honey industry to see if that’s something they want to use as an argument or not. Certainly, we can differentiate them and it’s not a subtle difference based on the chemistry we detected."
Retail honey samples labelled as mānuka or "tea tree" honey sourced from New Zealand and Australia were measured using REIMS in positive and negative ionisation modes.
The machine rapidly analyses hundreds to thousands of small molecules in a sample.
Dr Ross said the instrument measured the weight of electrically charged molecules to identify them.
A laser would "zap" a honey sample and the mass spectrometer would measure the metabolites in the honey vapour within 10 seconds, he said.
The advantage of this was that many samples could be quickly screened, he said.
To be exact, a total of 1637 metabolite features (molecular compounds) were found for New Zealand mānuka honey and 1744 for Australian mānuka honey. The REIMS’ fingerprinting strongly reflected their country of origin even though they had a similar MGO content.
So is New Zealand mānuka honey better than its Aussie cousin?
Dr Ross said they tried to match the honeys for MGO — the component benchmarking the potential antiseptic benefits.
"They are roughly matched for that and even with that being equal we are still seeing this big difference. From what we’ve done we can’t say anything about whether there’s a higher level of bioactive components or not. That’s not something we’ve dug into, so I can’t really comment sorry about whether one’s better than the other. But what we can say is the honey is certainly different and it would be interesting for someone to do that comparison with some kind of assay to look at the bio-activity, but that’s not something we’ve done."
Technology often raised more questions than it gave answers, he said.
To the naked eye some of the Australian honey samples looked much like New Zealand mānuka honey and others resembled thick tar or a Vegemite texture.
The first thing to come out of the data was their country of origin, reinforcing there is something quite clearly imprinted in honey that is related to where it comes from geographically.
Dr Ross said the Ministry for Primary Industry’s (MPI) definition of mānuka honey was based on a different mass spectrometry method.
"That method works well, but it takes a bit of time to prepare the sample and you have to extract it before you run it through the mass spectrometer. With this we basically zap it and the vapour is formed within a few seconds so the mass spectrometer is detecting what’s in that vapour. So it’s a high-frequency throughput method and it’s only been applied once to honey samples. The method itself was actually developed over real-time cancer surgery so a surgeon could detect where the borders of tumours were when they were cutting around a tumour. We have really taken that technology and applied it to food and agricultural products."
This opened up opportunities for future verification of food products, he said.
So far, the technology has been applied to meat to find out what lambs have been eating so scientists can tell the difference between different pastures and work out how stress affects their growth.
The honey study was initiated after the New Zealand mānuka Honey Appellation Society showed interest in the technology and made inquiries with Dr Ross about whether it could be applied to mānuka honey.
Now complete, it was funded by Te Pitau, the operating arm of the mānuka Charitable Trust, which was formed to protect mānuka honey on behalf of iwi, and the government’s Provincial Growth Fund.
Dr Ross said the work showed the technique could be used to identify the origin of honey samples within the fingerprint of measurements by the mass spectrometer.
They were also able to identify some of the components of the MPI’s definition for mānuka honey, he said.
The MPI’s molecular definition for mānuka honey verification included DNA analysis of the mānuka trees’ pollen and specific metabolites such as 2’-methoxyacetophenone (2’-MAP) and 2-methoxybenzoic acid (2-MBA).
The study supported that these markers, unique to mānuka honey, could also be used to determine a sample’s geographic origin.
"Potentially, there’s information that goes beyond just the geographical location or origin and that’s what’s exciting about the technology. Because we’re measuring a thousand or so things in that sample rather than just one or two, you get this really broad-based picture. So when we say we can tell the difference between Australian honey and New Zealand honey, we are not saying here is this magical molecule that differentiates between Australia and New Zealand — it’s based upon a few hundred molecules and how they relate to each other and we’re able to get a lot more detail from a really fast measurement."
The results are also expected to help counter fraud by verifying the chemistry of food claims.
Honey is said to be among the most faked food products in the world.
False labels are a problem and, in some cases, syrup is being added to cheaper honey to mimic the brown colour of mānuka honey in a bid to pass the honey off as the more expensive product. Another ruse is the altering of it by adding MGO and another compound known as dihydroxyacetone (DHA). MGO is created in mānuka honey thanks to the conversion of DHA, a high concentration of which is found in the nectar of mānuka flowers.
Dr Ross said the REIMS technique could be a valuable tool for the honey industry, consumers and regulatory bodies to verify mānuka honey.
"Our study reinforces the idea that the geographical origin of Leptospermum honey is deeply embedded in its molecular makeup. This knowledge can help ensure the authenticity and quality of mānuka honey, protecting both consumers and the industry."
The study found the REIMS features, particularly in negative ionisation mode, correlated strongly with established molecular markers used to assess the quality of mānuka honey, he said.
"We’ve got to be a bit careful about saying what we can prove and what we can’t prove because this is just one study. The MPI definition worked equally well to differentiate between the Australian and the New Zealand honeys. So really what we’ve got is a technology that can do the same sort of thing, but do it faster. What we also found with all the honeys there were no outliers, so we weren’t looking at anything that was fake honey. I guess what we want to do as a next step might be to create some fake honeys and see how well that was picked up."
A study in China found that a honey substitute made of corn syrup and rice syrup was easy to detect because honey was more complex than the syrups.
"So we expect it would be very good for picking up fraudulent mānuka honey. I guess where it gets a little bit controversial is if it comes from Australia does it make it fraudulent? I’m not going to touch that one with a 50-foot barge pole."
