A short history of the various rating systems for mānuka honey:
TA / NPA / UMF / MGO / MG / MGS / AAH / Pollen Percentage / KFactor / MQS.
By Bruce Roscoe
The Early Years
One honey type, 10 rating systems. And each is followed by a numerical value and a "+" mark, or a percentage sign. What to do? Luckily, we need understand only two of the above abbreviations. The others should then fall into – or out of – place.
Let's begin with the unlocking keys of the two abbreviations TA (total activity) and NPA (non-peroxide activity) and transport ourselves to the Waikato of the 1980s. This brief excursion will help us understand the issues besetting mānuka honey ratings today.
Two United Kingdom emigrants learned in Waikato in the early ‘80s that mānuka honey had uncommon antibacterial strength. One, Kerry Simpson, was a science teacher at Otorohanga College and the other, Dr Peter Molan, a lecturer in biochemistry at the University of Waikato. Although Dr Molan is known as the father of mānuka research, he is more accurately stepfather, for it was Mr Simpson who began the experimentation in Dr Molan's laboratory in January 1980, during the university's summer break.
The scientific method underlying the experimentation could be traced to the 1860s and cradled names such as Julius Petri (the Petri dish), Robert Koch (who isolated the species of bacteria that caused tuberculosis) and Louis Pasteur (who heated beverages to kill bacteria; pasteurization).
A common strain of bacteria would be placed on a glass dish and fed agar, a substance derived from seaweed, so that it would grow. Honey would be placed on the same dish. The area － called "zone of inhibition" － in which the bacteria did not grow would then be observed as proof of antibacterial activity.
Mr Simpson and Dr Molan first conducted this test on mānuka and two other honey types. Mānuka honey was most lethal against the bacteria. This test result had shown the "total antibacterial activity" or TAA of the honey. TAA was shortened to TA. At this stage no numerical values (such as 5+ or 10+) were assigned to the result.
Mindful that nearly all honeys were antibacterial, owing to hydrogen peroxide content, Mr Simpson and Dr Molan conducted a second experiment. They neutralized the hydrogen peroxide content of the three honeys by adding the enzyme catalase. When they then repeated the first test they found that only the mānuka had retained its antibacterial strength.
They had discovered that there was SOMETHING ELSE in the mānuka honey. They described the antibacterial strength of the mānuka as non-peroxide activity, or NPA.
Excitement arose when in repeated tests some mānuka samples showed markedly high antibacterial strength. Too, the possibility loomed that while hydrogen peroxide as a liquid degrades when exposed to heat and light, the unknown active compound in mānuka could retain its strength over time, which later proved to be the case.
Research papers followed － among them the 1983 MSc thesis "Antibacterial properties of honey" by University of Waikato student Kathryn Russell; the paper "A comparison of the antibacterial activity of some New Zealand honeys" (Molan, Smith, Reid) in the Journal of Apicultural Research, 1988; and the paper "Identification of some antibacterial constituents of New Zealand mānuka honey" (Russell, Molan, Wilkins, Holland) in the Journal of Agricultural and Food Chemistry 1990.
A Private Meaning of "Unique"
The UMF Honey Association (UMFHA) registered UMF™, which abbreviates "Unique Mānuka Factor", as a trademark in April 1988. (The association itself would not formally register as the Active Mānuka Honey Association Inc. until September 2002; the name change to UMF Honey Association Inc. was recorded in July 2011.)
SummerGlow Apiaries Ltd as UMFHA member and licensee No. 1001 was present from the dawn. Founders Bill and Margaret Bennett lay claim on their website to having pioneered the "highly-revered and trusted quality trademark UMF" in 1988. Throughout, on the websites of members of the association, the sense in which the word "unique" is used is unexplained. Dr Molan had chosen the word. It was to say, "We cannot identify the compound most responsible for the antibacterial strength of mānuka honey and, until we can, we shall call it 'unique'".
For the next 10 or so years, until two research papers － one German in 2008, one New Zealand in 2009 － identified methylglyoxal as the "unique" compound, UMF licensees would print the trademarked UMF on labels while non-licensees had to settle for NPA. Still other producers or packers settled for the hydrogen peroxide test and labeled their products TA for "total activity".
Dr Molan, in 1995, had established the Honey Research Unit at the University of Waikato, which he would direct until 2013. The numerical values of say 10+ or 15+ that would become mānuka honey ratings were his creation as consultant to UMFHA, which he had joined. Using the bacterium Staphylococcus aureus in the diffusion assay, similar to that used in his laboratory in the summer of 1980, he measured the antibacterial strength of the common antiseptic phenol. He diluted phenol with water, creating solutions for example of 10% and 15%. He then repeated the tests using mānuka honey, and compared the results with those for phenol. If the mānuka result exceeded that achieved with the 10% phenol solution, the mānuka could be labelled UMF10+ (or NPA10+). And so on with 15% and higher phenol solutions which became UMF15+ and higher grades.
UMF under threat from MGO
The methylglyoxal discovery threw a wallet of multi-sized spanners into the UMF works, and some of those spanners still cruise the air. Methylglyoxal content could be measured in milligrams per kilogram of honey and the lengthy name abbreviated as MGO. In the case of UMF, no one knew the object of measurement. They knew only that it was not hydrogen peroxide, hence the term "non-peroxide activity". It is more convincing to say what something is than what it is not. Too, MGO values easily could exceed 100 or 200 or soar to 800 or top 1,000, all followed by a "+" sign. With the exception of blood pressure and golf scores, consumers would eat up the higher numbers (exam results, bonus payments…).
Some packers, who seemingly did not understand that Mānuka Health New Zealand Ltd had trademarked only a polygon shape enclosing the letters MGO and not the abbreviation itself, out of misplaced fear began to use MG instead of MGO. Parenthetically, the registration by the Japan Patent Office of MGO as a trademark of TCN Co., Ltd, in January 2011 seemed unnoticed in New Zealand. The trademark － No. 5380195 － was renewed in July 2020. TCN is a Nagoya-headquartered importer and online seller of mānuka honey.
If UMF overnight had become less valuable as a measurement, it nonetheless continued to hold value as a widely recognized brand. Offshore companies still sought to become licensees. The logo remained a target of counterfeiters. Moreover, substantial investment in the brand had been made by bona fide producers, importers, wholesalers, and retailers.
UMFHA's response was to cry out for research that would correlate MGO with NPA values so that it could align its UMF10+ or UMF15+ values with MGO near equivalents. Which it did. Except there was a misstep.
Scholars of the University of Waikato responded to the call. Their timing evinced early access to the German and New Zealand papers published in 2008 and 2009. The Chemistry Department of the University of Waikato in November 2007 presented a paper to the journal Carbohydrate Research showing, in graphic and tabular form, a correlation between NPA and MGO values. This paper, "Isolation by HPLC and characterisation of the bioactive fraction of New Zealand mānuka (Leptospermum scoparium) honey", would serve to re-legitimise the UMF rating system and protect the brand.
The speed to publication was breakneck, compared to the glacial pace that is usual in the case of scholarly journals. The paper, which had as many as seven authors, had been presented on 7 November, presented again in a revised version on 11 December, and accepted on 17 December. The authors and peer reviewers should have placed a higher value on sleep. All correlations in the key table matching UMF with MGO values had been miscalculated and required upward revision by a factor of 1.87. The subsequent paper of correction, seemingly disguised by the Latin term "corrigendum", is still cited in reports today by laboratories commissioned to conduct MGO analysis and reverse calculate to UMF (NPA) values.
Dr Molan Deserts UMFHA
As a result of argument over mānuka honey grading methodology Dr Molan, whom the University of Waikato had elevated to professor of biological sciences in 2003, ended his 15-year relationship with UMFHA in December 2008. The argument culminated in Dr Molan giving evidence in support of Watson & Son in the case UMFHA brought against that company in order to expel it from the association over the claim that mānuka honey products it exported to the United Kingdom were not true to their stated UMF rating.
Although UMFHA succeeded in its case, Dr Molan and Watson & Son responded by launching the Molan Gold Standard (MGS) rating system which would compete with UMF. This system comprises the four grades 10+, 12+, 16+, and 20+ which correlate to methylglyoxal content of 300, 400, 600, and 800 milligrams per kilogram of honey.
Dr Molan wrote in his article ‘The true relationship of NPA and MG levels’ in New Zealand Beekeeper (April 2015): "...the NPA rating starts at 8, not zero, a rating of 8 being the minimum level of activity that can be detected in the assay". In that conviction lies the kernel of his dispute with UMFHA, whose members of size had clamoured for UMF grades to begin at 5+.
An Edison investment report (August 2014) on Comvita noted that the UMF5+ grade was the company's "standard honey offering". Then, as now, Comvita was New Zealand's largest exporter of mānuka honey and also largest single source of levy revenue for UMFHA. While Dr Molan would have wished to bend the business to fit the science, UMFHA appeared to have bent the science to fit the business.
UMFHA on its website claims to have “founded the science of mānuka honey 25 years ago”, thus expunging the contribution of Dr Molan over 20 years. Yet the site does place “Professor Peter Molan”, who died in 2015, ninth on a list of 12 “key researchers”.
Within two years of Dr Molan's passing Watson & Son had modified the MGS standard by adding a 5+ rating. Science again appeared sidelined for the sake of business, despite the guide to the standard stating: "If you are looking for the real thing, look for the Molan Quality StandardTM Quality Mark with a rating of at least 10+ and a methylglyoxal content of ≥ 300mg / kg on the label..."
The Regulator Intervenes
Mānuka honey ratings were conflicted from the outset. The numerical values indicated degrees of antibacterial strength which implied efficacy against medical conditions. But, unlike pharmaceutical products that in clinical trials had proved curative effect, mānuka honey was a food. A regulatory hammer would fall on both sides of the Tasman, but it fell hardest on New Zealand honey producers as each country unilaterally interpreted a bilateral standard.
Under standard 1.2.7 (see Section 8) to the Australia New Zealand Food Standards Code introduced in 2013, the Ministry for Primary Industries (MPI) ruled in July 2014 that claims such as "Non-Peroxide Activity", "Total Peroxide Activity", "Peroxide Activity", "Total Activity" and "Active" were to be removed from labels and advertising by January 2018 at latest.
UMF ratings, too, were viewed as non-compliant. Labels could show information only about the content of the honey. Which left no alternative than to bring MGO to the fore as methylglyoxal was expressed in milligrams per kilogram of honey.
For a time rumours were rife that MPI would outlaw the UMF rating system. MPI agreed to a UMFHA request to provide a letter confirming that the ratings could remain. "I write to confirm that the revised UMF grading system which is outlined on the UMFHA website...is in line with the 'Interim Labelling Guide for Mānuka Honey' and the legislation the guide is based on", Jenny Bishop of MPI's Food Science and Risk Assessment Directorate wrote to then UMFHA general manager John Rawcliffe on 9 April 2015. In addition to methylglyoxal, the association had added two compounds (dihydroxyacetone and leptosperin), whose content could also be measured in milligrams per kilogram of honey, to the UMF grading system.
Australian “manuka” honey producers faced no regulatory constraint in using words such as "Active", "Activity", or "Bioactive" on product labels or in advertisements.
Outliers
Airborne Honey Ltd manuka product labels in the past have carried the abbreviation "AAH" followed by a numeral and a plus mark, which represented a hydrogen peroxide measure of antibacterial strength. Airborne most recently abbreviated AHH as "Airborne Active Honey", though one edition of the company's website stated AHH as "Antibacterial Antioxidant Honey". The now abandoned New Zealand trademark registration recorded only "Airborne AAH". In response to MPI's interpretation of Standard 1.2.7 Airborne discontinued its AHH ratings and introduced manuka pollen percentage values ranging from 30% to 85%.
MQS abbreviates "mānuka quality system" which is operated by Avatar Honey NZ Ltd. MQS combines MGO with pollen analysis. The latest laboratory reports posted to the Avatar website are dated August 2017 and the pollen type tested is recorded as "mānuka / kanuka".
KFactor™ is a brand operated by Wedderspoon Organic USA LLC. When followed by the numeral 12 the product is labelled as multifloral mānuka honey, while the numeral 16 is used on monofloral mānuka labels. Wedderspoon’s website does not elaborate on the meaning of KFactor and the company has not responded to a query about its meaning. Without sighting a batch-specific laboratory report, it is not possible to understand what if any meaning KFactor may have beyond denoting a corporate brand.
Websites dedicated to the MGS and MQS ratings are inactive. MGS is used by perhaps no more than three brands whose underlying producers are undisclosed.
Bees Keep Secrets
MGO dominates mānuka honey ratings. UMFHA brand guidelines accommodate dual UMF and MGO ratings on labels. The size and positioning of MGO values has changed from small lettering on the back of the labels to larger lettering on the front. In many cases, if not most, when UMF licensees export bulk monofloral mānuka or retail pack product for private-brand use, the labels will show MGO values as UMF values cannot (or should not) be used by non-licensees.
Food testing laboratories now only rarely, if ever, use the agar diffusion method for measuring the NPA of manuka honey. Hill Labs first tests for MGO content. In reports Hill Labs states both MGO values and correspondent NPA values which it calculates according to corrected published research. UMF licensees rename the NPA values as UMF™, while non-licensees use them under the same NPA abbreviation. Analytica Laboratories reports similarly state MGO and NPA values while noting that the calculated NPA values are not accredited by International Accreditation New Zealand. Awanui Scientific reports confirm that “NPA is calculated as % phenol equivalent from the measured MGO concentration in the honey”. Analytica adds that the peroxide activity (PA) test is still commonly used for high activity, non-manuka honeys such as kanuka, jarrah, and marri.
Methylglyoxal was described as the "dominant" antibacterial constituent of mānuka (Leptospermum scoparium) honeys from New Zealand in the 2008 paper produced by faculty of the Technical University of Dresden.
Scholars reporting to the American Laryngological, Rhinological and Otological Society in 2011 concluded that MGO was "only partially responsible for the antibiofilm activity of mānuka honey". There is still "something else" in the mānuka. Something unique. That "something" remains a secret to bees.
"The Early Years" section of this report owes much to Cliff Van Eaton's excellent book Mānuka － the biography of an extraordinary honey (Exisle Publishing, Auckland 2014).
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