Manuka Honey and Heat: What Really Happens to MGO When You Heat It

Manuka honey and heat get blamed for a lot of things online, usually with a hard rule attached: never let it near anything above 40°C, or you've wasted your money. That rule is mostly wrong. It confuses two very different things: how sensitive honey's natural enzymes are to warmth, and how sensitive MGO (methylglyoxal), the compound that gives Manuka honey its antibacterial strength, actually is. The real picture is more useful, and more specific, than a single temperature ceiling.

Key Takeaways

• MGO is far more heat stable than most online advice suggests, holding up well to temperatures around 90°C rather than the commonly quoted 40°C.
• Antibacterial strength in Manuka honey tracks closely with MGO concentration, so protecting MGO during storage and use directly protects the honey's medicinal value.
• The main damage from heat comes from sustained exposure at high temperatures (think baking or candy making), not from a brief stir into a hot drink.
• Because heat genuinely can degrade bioactivity at the wrong temperatures, honey that is never heat-treated during production, like Biosota's, starts from the strongest possible baseline.

The short answer: it depends on the temperature and the time

Early lab research on manuka honey and heat suggests MGO doesn't disappear the moment it meets warmth. In controlled heating experiments, MGO stayed close to its starting level up to around 90°C, with only modest loss after an hour at that temperature. It was sustained heat well above that point, and especially heat combined with time, that caused the bigger drops.

That single distinction, temperature alone versus temperature plus time, explains why so much consumer advice about Manuka honey and heat is contradictory. A quick stir into a cooling cup of tea and a 10 minute bake at candy-making temperatures are not the same event, even though both technically involve "heating" the honey.

What MGO actually does, and why heat matters

MGO is the compound responsible for most of Manuka honey's non-peroxide antibacterial activity, the part of its effect that doesn't rely on the hydrogen peroxide found in regular honey. Research comparing commercial Manuka honeys suggests antibacterial strength climbs steadily as MGO concentration rises, from an AAV (antibacterial activity value, a separate lab-assay score, not another mg/kg figure) of around 270 at 50 mg/kg MGO up to roughly 647 at 1000 mg/kg MGO. In other words, MGO isn't just a label number. It's doing measurable work, and that work scales with how much of it survives in the jar.

Reviews of Manuka honey's antibacterial mechanism note that MGO accounts for most, but not all, of that activity. Other factors, like the honey's natural acidity and osmotic effect, contribute too, and neutralising MGO alone doesn't fully eliminate antibacterial action against every bacterial strain tested. So while MGO is the headline compound, it's one part of a broader defence system, which is worth knowing before assuming any encounter between manuka honey and heat "cancels out" the honey entirely.

The science: how heat breaks down MGO

Here's where manuka honey and heat get genuinely interesting from a chemistry standpoint. Heat doesn't simply "burn off" MGO the way it might evaporate water. Early lab research suggests MGO reacts with amino acids naturally present in honey, binding to them chemically and converting into new, non-antibacterial compounds. This binding reaction speeds up as temperature rises, which is the real mechanism behind MGO loss during heating.

A related compound called MAP, used as a marker of genuine Manuka honey, is lost through a completely different process: it simply evaporates into the air above the honey as it heats, more so in an open container with more air space above the honey. So MGO is chemically transformed, while MAP physically escapes. Both point to the same practical takeaway: sustained heat changes the honey's chemistry, it doesn't just "warm it up."

The numbers: MGO loss at different temperatures

Manuka honey and heat interact differently depending on exactly how hot, and for how long. To make this concrete, here's what early lab research on manuka honey and heat has measured:

• Around 90°C for 1 hour: roughly 17% MGO loss
• 90°C for 2 hours: more than 55% MGO loss
• 150°C for 10 minutes (similar to candy-making conditions): MGO can fall to around 12% of its original level

The pattern is clear: short exposure at moderate heat causes limited damage, while prolonged exposure at high temperatures causes serious damage. A separate heating study on Manuka honey's ingredients points in the same direction, suggesting MGO held steady up to around 90°C, with a much sharper drop above 100°C, and the sharpest drop of all at sustained temperatures of 120°C and higher. That study's authors recommended keeping processing temperatures as low as possible and heating times as short as possible. It's exactly the guidance a careful Manuka honey user should follow at home too.

It's worth being precise about what this research does and doesn't show. These figures come from lab measurements of MGO concentration itself, not from a direct test of antibacterial activity after heating. Because antibacterial strength tracks so closely with MGO level, a large drop in MGO almost certainly means a real drop in antibacterial potency. But that's an inference from the MGO-activity relationship. It's not something these particular heating studies measured directly.

The myth: "never let it near anything hot"

Most confusion about manuka honey and heat comes down to a single mixed-up rule. This is where a lot of well-meaning advice goes wrong. Many sources online recommend keeping Manuka honey below 40°C at all times, warning that anything hotter destroys its benefits. That advice isn't really about MGO. It's about honey's natural enzymes, like glucose oxidase, which are genuinely more heat-sensitive and start losing activity in that lower temperature range.

MGO is a different molecule with a different tolerance. Conflating enzyme sensitivity around 40°C with MGO's actual stability up to around 90°C leads to overly cautious rules that don't match what the chemistry shows. A broader study on heating honey (not limited to Manuka) found that even gentle heating, around 45 to 65°C for an hour, left antioxidant markers largely unchanged while still reducing antimicrobial activity somewhat, a reminder that different bioactive components respond differently to the same amount of heat. The practical upshot: a cup of tea that's cooled from boiling for a minute or two sits well within MGO's stable range, even if it's warm enough to start affecting some enzymes.

How to use Manuka honey without wasting its potency

Given what the research on manuka honey and heat actually shows, a few practical habits protect MGO without requiring you to eat Manuka honey straight off the spoon at room temperature forever.

For hot drinks, letting boiling water cool for a minute before stirring in honey keeps you well within MGO's stable range. For cooking and baking, save your highest-MGO, most expensive jars for uses where they aren't exposed to sustained oven or stovetop heat. Drizzle it over warm, not hot, food instead, or add it right at the end of cooking. If a jar has crystallised, a gentle warm water bath, kept well below 40°C, softens it without meaningfully affecting MGO. For everyday guidance on getting the most from your Manuka honey, see how to use Manuka honey for the best results. For more on storage conditions and shelf life, see does honey crystallisation, temperature, or shelf life impact the medicinal qualities of Manuka.

This is also part of why Biosota takes manuka honey and heat seriously at the production stage: the honey is never heat-treated, pasteurised, or sterilised. Since heat is the one variable proven to degrade bioactivity, avoiding it at the production stage means every jar starts from its full natural MGO strength. That's before it ever reaches your kitchen. To find the right MGO strength for your needs, explore Biosota's Manuka honey guide, or browse the full range of Biosota Organics Manuka honey.

References

1. Kato, Y. et al., "Methylglyoxal binds to amines in honey matrix and 2'-methoxyacetophenone is released in gaseous form into the headspace on the heating of manuka honey", https://doi.org/10.1016/j.foodchem.2020.127789 (2021) (preliminary, in vitro lab chemistry study)
2. "Thermal stability of manuka honey's characteristic ingredients", Cookery Science journal, https://www.jstage.jst.go.jp/article/cookeryscience/54/4/54_186/_article/-char/en (2021) (preliminary, in vitro lab chemistry study; author not independently confirmed beyond abstract access)
3. Green, K.J., Lawag, I.L., Locher, C., Hammer, K.A., "Correlation of the antibacterial activity of commercial manuka and Leptospermum honeys from Australia and New Zealand with methylglyoxal content and other physicochemical characteristics", https://doi.org/10.1371/journal.pone.0272376 (2022)
4. Johnston, M. et al., "Antibacterial activity of Manuka honey and its components: An overview", https://doi.org/10.3934/microbiol.2018.4.655 (2018)
5. Mat Ramlan, N.A.F. et al., "Application of Heating on the Antioxidant and Antibacterial Properties of Malaysian and Australian Stingless Bee Honey", https://doi.org/10.3390/antibiotics10111365 (2021) (general honey study, not Manuka-specific)