Mānuka Honey is so famous, we know. But it comes with different rating systems, using numbers and acronyms, that are just so confusing!
What is UMF? What is MGO? What does 10+ or 500+ mean when used in these rating systems for Mānuka Honey. How is it that these different rating systems evolved? Is one system for rating Mānuka Honey better than the other? And, just what do these rating systems for Mānuka Honey actually mean?
In this article, we will answer all your questions about UMF and MGO rating systems and demystify all about the grading of Mānuka Honey.
UMF vs MGO: The History of Rating Mānuka Honey
Professor Peter Molan (centre) with his team at Waikato University in New Zealand. Dr Molan is credited with the discovery of the non-peroxide activity (NPA) of Mānuka Honey in the late 1980s. He pursued a programme of research into the properties and potential applications of Mānuka and other New Zealand honeys, that paved the way for the growth of New Zealand’s honey industry and the phenomenon of Mānuka Honey as one of the world’s most sought-after honeys. Photo Credit: Shane Morton/Fairfax NZ
Mānuka Honey and Non-Peroxide Activity (NPA)
The fame of Mānuka Honey stems from the nature of its antibiotic properties, that sets it apart from other honeys. The main drivers of antibiotic activity in most honeys is hydrogen peroxide, produced when glucose oxidase, which comes from the honey bee, reacts with glucose and water. Other factors in the anti-bacterial effect of honey are high sugar concentration and the low pH acidic nature of honey (see our blog Benefits of Honey in Healing Wounds on these factors).
In the late 1980s, Professor Peter Molan of Waikato University in New Zealand, found that in Mānuka Honey, when its hydrogen peroxide content and other factors in antibiotic activity are neutralised, the antibiotic activity still remains. With this exciting discovery, Molan then ran a programme of research that explored these properties, testing the activity of Mānuka Honey against a range of different bacterial species.[1]
Throughout this research programme, while Molan found that even relatively low concentrations of Mānuka Honey were effective against bacterial pathogens, the specific active ingredient responsible for this anti-bacterial activity was not known.
Without knowing precisely what caused the antibiotic activity in Mānuka Honey, scientists at the time simply dubbed it to be “non-peroxide activity” or NPA.
In those days, NPA was measured using a test in a Petrie dish of agar that compares the honey in antibiotic activity with different strengths of phenol, a well-known anti-biotic. The numbers in the scale for NPA related to the equivalent % strength of phenol, in destroying bacteria grown in the Petrie dish culture, ranging usually between 5+ and 25+. So, NPA 5+ Mānuka Honey has the same anti-bacterial activity as a 5% solution of phenol, and a 10+ Mānuka Honey has the same effect as a 10% phenol solution, and so on.
In this way, the NPA scale became an early system for rating Mānuka Honey. But still, the compound in Mānuka Honey responsible for its anti-bacterial activity remained elusive.
Advent of ‘Unique Mānuka Factor’ or UMF for Rating Mānuka Honey
Whilst NPA was a useful early rating system for Mānuka Honey, it was a descriptive term used by scientists studying the chemistry of honey and it did little for the imagination of the consumer in market. Furthermore, Professor Molan had discovered that it was only Mānuka that exhibited NPA, and so, accordingly, he coined for it the term ‘Unique Mānuka Factor’ or UMF.
The popularity and value of Mānuka Honey grew through the 1990s and in 1998, a small group within the honey industry in New Zealand moved to protect UMF through trademarking. Later, in 2002, users of the UMF trademark came together to form the Unique Mānuka Factor Honey Association (UMFHA).
At that time, UMFHA members used UMF ratings on their labels for Mānuka Honey derived directly from the results of tests for NPA. So UMF 5+ was used for Mānuka Honey testing as NPA 5+ and, UMF 10+ was used for NPA 10+ and so on.
Other producers of Mānuka Honey would simply use the results of their NPA tests as a rating system on their labels. The simple and direct relationship between UMF, NPA and the phenol test is set out in Diagram 1 below.
Diagram 1: Relationship Between Phenol Tests, NPA and UMF (in early 2000s)
| Concentration of Phenol | Non-Peroxide Activity (NPA) | Unique Mānuka Factor (UMF) |
| 5% | 5+ | 5+ |
| 10% | 10+ | 10+ |
| 15% | 15+ | 15+ |
| 20% | 20+ | 20+ |
| 25% | 25+ | 25+ |
All that time, the actual chemical identity of the ‘unique manuka factor’ and the compound causing the ‘non-peroxide activity’ in Mānuka Honey had not been identified.
Discovery of Methylglyoxal in Mānuka Honey
Then, in 2006, scientists discovered that methylglyoxal (MGO) is the compound in Mānuka Honey that is primarily responsible for its non-peroxide antibacterial activity. It appeared that the ‘unique manuka factor’ had finally been revealed.
This major discovery is usually attributed to Professor Thomas Henle and his team in the Institute of Food Chemistry at the Technical University of Dresden in Germany[2] but it was also independently discovered and published at about the same time by a group of researchers at Waikato University.[3]
Studies of MGO in Mānuka Honey showed that levels of MGO related directly to the honey’s non-peroxide antibacterial activity or NPA. That is, the higher the antibacterial activity, the higher the MGO concentration.
The relationship between MGO and NPA is commonly presented in a graph as follows.
Diagram 2: Relationships between MGO and NPA in Mānuka Honey.[4]
From this relationship, and the widening understanding of MGO as the ‘unique manuka factor’ in Mānuka Honey into the 2010s, MGO then became yet another way of rating Mānuka Honey. At that time the relationship between the rating systems was clear, as set out in the table below.
Diagram 3: Pre-2014 Relationship Between Phenol Tests, NPA and UMF
| Concentration of Phenol | Non-Peroxide Activity (NPA) | Unique Mānuka Factor (UMF) | Methylglyoxal (MGO) mg/kg |
| 5% | 5+ | 5+ | 83 |
| 10% | 10+ | 10+ | 263 |
| 15% | 15+ | 15+ | 514 |
| 20% | 20+ | 20+ | 829 |
| 25% | 25+ | 25+ | 1197 |
Mānuka Honey and New Zealand Labelling Standards
By the early 2010s, the range of scales for rating Mānuka Honey were used, and also abused, in product labelling and promotion in a way that created not just confusion, but also scandals, in market. The New Zealand government stepped in to set labelling standards in order “to ensure that mānuka honey products are true to label and not misleading for consumers.”[5]
The Interim Labelling Standard comprehensively covered matters relating to the labelling of Mānuka Honey, and was clear on what ratings scales could be used.
- Health claims could not be made, so that terms such as NPA, peroxide activity, bioactivity or other such terms could no longer be used on honey labels.[6]
- Content information such as for MGO was deemed allowable.[7]
- Grading systems based on parameters which are therapeutic claims or health claims were deemed not allowable.[8]
Of the systems for rating Mānuka Honey in place at the time, NPA was gone and MGO was in. It was simple for Mānuka Honey Producers using the NPA rating scale to change directly to MGO. Others were already using MGO and looked to the new standards as vindication for their approach.[9]
But the Interim Labelling Standard appeared to create an issue for UMF users, as it appeared to disallow the use of UMF as a rating scale on labels for Mānuka Honey. This was not an insignificant matter for the New Zealand honey industry. Many producers of Manuka Honey in New Zealand used the UMF scale and as members of the UMFHA, they had invested a lot into the UMF brand since the association was formed in 2002.
As it turned out, the matter was simply resolved by UMF removing NPA as the basis for its rating scale and adopting MGO, using the correlation between MGO and NPA as set out in Diagram 2 above. Accordingly, the phenol-based NPA tests are now seldom performed for testing and rating Mānuka Honey in New Zealand. Instead NPA (and UMF) are derived from an MGO test of Mānuka Honey, as can be seen in the explanation of results from an accredited laboratory below.
Diagram 4: NPA is derived from the laboratory testing of MGO in Mānuka Honey.
The test for MGO is the main test performed on Mānuka in order to determine its grade, whatever grading system – MGO or UMF – is used. It’s important then to turn to take a closer look at MGO and how MGO is dealt with in the production and grading of Mānuka Honey.
Methylglyoxal – MGO
What is MGO?
MGO, also represented as MG, stands for methylglyoxal, an organic compound with the formula CH3C(O)CHO or C3H4O2.
Diagram 5: The chemical composition of methylglyoxal
MGO is the naturally occurring compound in Manuka Honey that gives it antibiotic and healing properties.
Where does MGO come from in Mānuka Honey?
MGO is formed in Mānuka Honey, from the spontaneous dehydration of dihydroxyacetone (DHA), a compound that occurs naturally in the nectar of Mānuka flowers. Mānuka Honey freshly produced by bees can have low levels of MGO and high levels of DHA. Then over time, the levels of DHA can drop (and the MGO level will rise) as the DHA converts to MGO.[10]
Further, not all Mānuka Honey is created equal. Some Mānuka trees have more DHA in their nectar than others, and DHA and MGO levels in Mānuka Honey can vary greatly.[11]
The rate of conversion from DHA to MGO in Mānuka Honey is not a 1:1 process and depends on a number of factors including age and storage temperature. This conversion process typically slows right down when the ratio of DHA to MGO is 2:1[12] and this stage will often not be reached until the honey is at least 24 months old.
As the graph to the left shows, the MGO in Mānuka Honey will level out at the point when the conversion slows down, at about the 24-month mark. From there, as the Mānuka Honey continues to age the MGO level will actually drop back slightly from its highest point at about 30 months old, even though the DHA is continuing to decrease.
Diagram 7: DHA and MGO Change in Mānuka Honey at Storage Temperature 20°C.[13]
Increasing MGO in Mānuka Honey
The grade and price of Mānuka Honey increases as the MGO concentration increases. So commonly, producers ‘ripen’ or ‘mature’ their honey over time or with gentle warming in order to increase the concentration of MGO. This practice requires expert knowledge of Mānuka Honey’s response to storage conditions to maintain the high quality and properties of the Mānuka Honey. At higher temperatures, the graph of conversion of MGO to DHA in Mānuka Honey has quite a different curve – note how the MGO degrades after a high point at only 12 months old.
Diagram 8: DHA and MGO Change in Mānuka Honey at Storage Temperature 27°C.[14]
Aging or warming of honey also increases the level of 5-hydroxymethylfurfural (HMF) which is potentially a toxic compound in high concentrations, and must stay below 40 mg/kg according to international standards.[15] Therefore, there is a trade-off between storing or warming honey to maximise the MGO concentration and retaining a low concentration of HMF.[16]
Diagram 9: HMF Change in Mānuka Honey at Different Storage Temperatures.[17]
The MGO system for rating Mānuka Honey
As we have seen, MGO is the main determinant of the antibacterial activity of Mānuka honey, and the higher the concentration of MGO, the stronger the antibacterial effect of Mānuka Honey.[18]
So, the MGO rating scale for Mānuka Honey is simple: the higher the MGO level, the higher the grade and the more potent the anti-biotic properties of the Manuka Honey. The grades for Mānuka Honey in the MGO rating system can be any number from 30 (for a blend Manuka Honey blend) to over 1200 (very highest grade of Mānuka Honey). The table below sets out a selected set of MGO grades against potency and suggested uses of Mānuka Honey.
Diagram 10: Antibiotic potency for MGO Grades for Mānuka Honey.[19]
| MGO Grade for Mānuka Honey | Potency & Suggested Usage |
| MGO 50+ | Blend honey suitable for the table and heath maintenance |
| MGO 100+ | Entry grade with some antibiotic effect and general good health maintenance |
| MGO 200+ | Activity level adequate for application as an antibiotic treatment in wound care, oral care and digestive health |
| MGO 400+ | Potent activity level for application as an antibiotic treatment in wound care, oral care and digestive health. |
| MGO 800+ | Superior activity level for application as an antibiotic treatment in wound care, oral care and digestive health. |
| MGO 1200+ | Highest level of activity level for application as an antibiotic treatment in wound care, oral care and digestive health. |
Whilst there has been some trademarking of MGO, the rating system is open to all to use, wherever the producers may be from, so that the MGO system is used by many producers in New Zealand and Australia.
The UMF system for rating Mānuka Honey
UMF is the rating system for Mānuka Honey that is set up for use by honey producers who are members of the Unique Manuka Factor Honey Association (UMFHA).
As we have seen, whilst UMF was once backed by an NPA test, it is now based on tests for MGO, as well as leptosperin, DHA and HMF (hydroxymethylfurfural).
The UMFHA website[20] sets out 5 grades for Mānuka Honey defined as follows:
Diagram 11:
| Grade | MGO | Leptosperin | DHA | HMF |
| UMF 5+ | 83 mg/kg | >100 mg/kg | >150 mg/kg | <40 mg/kg |
| UMF 10+ | 261 mg/kg | >150 mg/kg | >250 mg/kg | <40 mg/kg |
| UMF 15+ | 512 mg/kg | >200 mg/kg | >400 mg/kg | <40 mg/kg |
| UMF 20+ | 826 mg/kg | >200 mg/kg | >500 mg/kg | <40 mg/kg |
| UMF 25+ | 1197 mg/kg | >200 mg/kg | >500 mg/kg | <40 mg/kg |
Leptosperin
Leptosperin is a compound found naturally in the nectar of mānuka flowers, and testing for this compound provides evidence that the honey tested is Mānuka Honey. The levels of Leptosperin required for the UMF rating system start at >100 mg/kg (for UMF5+), increasing to >200 mg/kg (for UMF 15+). For grades of Mānuka Honey higher than UMF15+, the Leptosperin levels required do not change beyond >200 mg/kg.
DHA
As we have seen, DHA is found in the nectar of the manuka flower and is known to slowly convert to MGO in Mānuka Honey, depending on age and storage temperature. In the UMF rating system, DHA is presented as an indicator that “in correct amounts ensures that the MGO levels will remain as tested throughout the life of the product.”
HMF
HMF can be harmful to humans at high levels and is found naturally in honey. HMF increases under long periods of storage or excessive heating, and so can be used as an indicator of excessive aging or heating of honey that can be undertaken to optimise levels of MGO in Mānuka Honey.
he UMF system sets its standard for HMF to be 40mg/kg, for all UMF grades. This standard is the same as an international standard set for HMF by the Codex Alimentarius Standard Commission.[21]
Is UMF or MGO Better – a Critical Review
UMF vs MGO: what’s the difference?
Our review of these rating systems has found that MGO and UMF are both commonly-used systems for grading Mānuka Honey. Both systems provide assurance to consumers on the antibacterial potency of Mānuka Honey because they both measure MGO content.
The key differences lie in UMF using indicators in its scale other than MGO – leptosperin, DHA and HMF.
“UMF is based on MGO anyway”
As we have seen, the level of MGO is the main determinant of the UMF grade. That is, if the MGO is high then the Mānuka honey can attract a high UMF rating. The other indicators do not determine the UMF grade. For example, a high rating in Leptosperin or DHA does not gain a high grade in UMF, if the MGO is low.
So, it can be argued that UMF rating system can be boiled down in essence to just MGO.
UMF ratings for DHA in question
A review of the DHA to MGO ratios in the table below for the UMF rating system shows the ratio starting at less than the commonly found 2:1 ratio, and reducing further through the grades. This suggests that the DHA levels for these grades are set way lower than common industry practice, and are not actually providing assurance to the customer on shelf-life as claimed.
Diagram 12: DHA:MGO Ratios for UMF Grades
| Grade | MGO | DHA | DHA to MGO Ratio |
| UMF 5+ | 83 mg/kg | >150 mg/kg | 1.8:1 |
| UMF 10+ | 261 mg/kg | >250 mg/kg | 0.95:1 |
| UMF 15+ | 512 mg/kg | >400 mg/kg | 0.78:1 |
| UMF 20+ | 826 mg/kg | >500 mg/kg | 0.61:1 |
| UMF 25+ | 1197 mg/kg | >500 mg/kg | 0.41:1 |
Further given the graphs in Diagram 7 presented earlier suggest that, for instance, the DHA level of 500 mg/kg is associated with levels of MGO much lower than those presented in the UMF ratings.
MGO is Simpler
Producers that use the MGO system would argue that this system is simpler and more straightforward to use, and easier for customers to understand. They say that MGO is what really matters in Mānuka Honey, and this test measures clearly and simply for the customer to easily understand what they are buying.
In contrast, the UMF rating system can be confusing for customers because of its complexity:
- UMF has four factors as the basis for its rating.
- The levels of each factor do not consistently change as you move through the grades.
- The UMF scale is not intuitive. UMF 20+ is not twice as strong as UMF 10+ – it is 4 times as strong.[23]
MGO Adulteration
It has been found that MGO can be added to Mānuka Honey to increase its grade, so it is argued that the UMF rating system guards against this kind of deception.
Only one case of MGO adulteration is known of, being brought before the courts in 2019.[24] So it appears that although this MGO adulteration is possible, it is not common at all in Mānuka Honey production in New Zealand.
Further, MGO adulteration is a risk to the integrity of both MGO and UMF scales.
Conclusion: MGO is better than UMF for rating Mānuka Honey
I can only conclude from this review that the MGO system comes up as a simpler and more direct way of grading Mānuka Honey, and UMF is over complex and confusing, even misleading, for that purpose.
But then, I acknowledge that my conclusion is reflected in the choice that we have made at Manawa Honey NZ for rating our Mānuka Honey, so the reader may interpret this view as biased. So, I acknowledge that there will be proponents of the UMF system for rating Mānuka Honey – producers and customers alike.
In the end, it is up to you, the customer, to assess the robustness and meaningfulness of each system as it presents for you. You will firstly want assurance with regard to potency that you gain through MGO that sits in both MGO and UMF systems. Then you might want assurance on other aspects of Mānuka Honey, depending on your specific needs, as provided in the UMF scale.
Whatever the case, you will need to get to know your honey producer so you know you can trust that your Mānuka Honey is actually what it is claimed to be, no matter which rating system is used. Consumers need to know that their honey has been produced to quality standards without adulteration and without production practices that can affect the quality of the Mānuka Honey.
Think about:
- Who owns the company that’s producing the Mānuka Honey?
- What’s their ultimate purpose or raison d’etre?
- What are their operational drivers?
- Where is the Mānuka Honey produced and packed?
- Where does the Mānuka Honey come from and how is it produced?
In the end, logos, trademarks, tables and ratings cannot replace the integrity of a business in producing Mānuka Honey that is high quality and true to label.
Yes, that’s my ultimate conclusion here. Find the Mānuka Honey producer that you can trust.
Brenda Tahi draws on a range of areas in her diverse experience for her writing. She has an MBA in Strategic Management from Henley College (UK) and has had careers in public sector management and governance in New Zealand. Brenda has also published research in topics ranging from public sector management policy to Māori history and traditional knowledge. Brenda is a trustee for the Tuawhenua Trust of Ruatāhuna, and, drawing on her hobby beekeeping, she was part of founding Manawa Honey NZ, of which she is now CEO.
[1] Non-Peroxide Antibacterial Activity in Some New Zealand Honeys
P. C. Molan & K. M. Russell Pages 62-67 | Received 20 Aug 1987, Published online: 24 Mar 2015
[2] https://pubmed.ncbi.nlm.nih.gov/18210383/: Mavric E., Wittmann S., Barth G. & Henle T. (2008) Identification and quantification of methylglyoxal as the dominant antibacterial constituent of Manuka (Leptospermum scoparium) honeys from New Zealand. Molecular Nutrition and Food Research 52(4):483‐9.
[3] https://pubmed.ncbi.nlm.nih.gov/18194804 Adams C. J., Boult C. H., Deadman B. J., Farr J. M. et al. (2008) Isolation by HPLC and characterisation of the bioactive fraction of New Zealand manuka (Leptospermum scoparium) honey. Carbohydrate Research 343(4):651‐9.
[4] https://export-x.com/2014/05/29/manuka-honey-mgo-umf-ratings-compared/
[5] https://www.mpi.govt.nz/news/media-releases/manuka-honey-guide-released/
[6] https://nelsonhoney.com/wp-content/uploads/2015/10/interim-labelling-guide-manuka-honey.pdf Paragraph 20
[7] https://nelsonhoney.com/wp-content/uploads/2015/10/interim-labelling-guide-manuka-honey.pdf Paragraph 37
[8] https://nelsonhoney.com/wp-content/uploads/2015/10/interim-labelling-guide-manuka-honey.pdf Paragraph 22
[9] https://www.scoop.co.nz/stories/SC1407/S00062/methylglyoxal-in-guidelines-for-labelling-manuka-honey.htm
[10] https://pubmed.ncbi.nlm.nih.gov/19368902/ C. J. Adams , M. Manley-Harris and P. C. Molan , The origin of methylglyoxal in New Zealand manuka (Leptospermum scoparium) honey, Carbohydr. Res., 2009, 344 , 1050 —1053
[11] S. Williams , J. King , M. Revell , M. Manley-Harris , M. Balks , F. Janusch , M. Kiefer , M. Clearwater , P. Brooks and M. Dawson , Regional, annual, and individual variations in the dihydroxyacetone content of the nectar of manuka (Leptospermum scoparium) in New Zealand, J. Agric. Food Chem., 2014, 62 , 10332 —10340
[12] https://pubmed.ncbi.nlm.nih.gov/22960208/ Atrott J, Haberlau S, Henle T. Studies on the formation of methylglyoxal from dihydroxyacetone in Manuka (Leptospermum scoparium) honey Carbohydr Res. 2012 Nov 1;361:7-11. doi: 10.1016/j.carres.2012.07.025. Epub 2012 Aug 8. PMID: 22960208
[13] https://www.analytica.co.nz/media/psacama2/manuka-2020-forecasting-the-change-in-3-in-1-results-for-manuka-honey_nz-beekeeper-july-2020.pdf
[14] https://www.analytica.co.nz/media/psacama2/manuka-2020-forecasting-the-change-in-3-in-1-results-for-manuka-honey_nz-beekeeper-july-2020.pdf
[15] https://www.fao.org/fao-who-codexalimentarius/sh-proxy/es/?lnk=1&url=https%253A%252F%252Fworkspace.fao.org%252Fsites%252Fcodex%252FStandards%252FCXS%2B12-1981%252FCXS_012e.pdf
[16] http://hdl.handle.net/10289/9323 Grainger, M. (2015). Kinetics of Conversion of Dihydroxyacetone to Methylglyoxal in Honey (Thesis, Doctor of Philosophy (PhD)). University of Waikato, Hamilton, New Zealand.
[17] https://www.analytica.co.nz/media/psacama2/manuka-2020-forecasting-the-change-in-3-in-1-results-for-manuka-honey_nz-beekeeper-july-2020.pdf
[18] E. Mavric , S. Wittmann , G. Barth and T. Henle , Identification and quantification of methylglyoxal as the dominant antibacterial constituent of Manuka (Leptospermum scoparium) honeys from New Zealand, Mol. Nutr. Food Res., 2008, 52 , 483 —489
[19] This table has been derived from a range of published tables setting out grades and suggested usages for Mānuka Honey. See https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7693943/ for relative anti-biotic effects of different grades of Mānuka Honey on a range of microbes. Also see https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3220139/ for effects of Mānuka Honey in oral care.
[20] https://www.umf.org.nz/
[21] https://bmcchem.biomedcentral.com/articles/10.1186/s13065-018-0408-3#ref-CR6
[22] https://www.umf.org.nz/unique-manuka-factor/
[23] https://researchcommons.waikato.ac.nz/handle/10289/9277 Molan, P, The True Relationship of NPA and MG Levels, New Zealand Beekeeper, April 2015, pp 14-18. In this article Molan explains that he considers that MGO
[24] https://www.rnz.co.nz/news/country/381426/manuka-honey-producer-charged-in-landmark-case