The sugars in honey

The two that do the work

Nectar arrives at the hive mostly as sucrose — the same molecule as table sugar, a fructose unit joined to a glucose unit. Invertase from the bee splits that bond, and what ends up in the comb is a mixture of the two halves rather than the intact pair. That single reaction is most of what distinguishes honey from concentrated nectar.

The ratio is the useful number

Glucose is far less soluble in water than fructose. Honey holds more glucose than water at that temperature can dissolve, so glucose is permanently on the edge of dropping out of solution — and a honey with proportionally more glucose crosses that edge sooner. The fructose-to-glucose ratio is therefore the single most predictive number about a honey's future texture.

• Ratio below about 1.0 — glucose-rich. Sets fast and hard. Rapeseed and dandelion can granulate in the comb before extraction.
• Ratio around 1.1 to 1.2 — the majority of honeys. Sets over weeks to months, usually with a coarse grain unless it is seeded.
• Ratio above about 1.3 — fructose-rich. Stays liquid for a year or more. Acacia and tupelo are the standard examples.

The ratio in real honeys

The rule above is a rule of thumb until it is checked against measured honeys, and the best check available is the European reference data: thousands of authentic samples of fifteen honey types, analysed by laboratories across the International Honey Commission and described by trained panels. The table sorts them by fructose-to-glucose ratio and puts the panels' own verdict on crystallisation in the last column.

The mechanism holds at both ends. Rape, dandelion and sunflower honeys, with ratios close to 1.0 and glucose-to-water ratios above 2, are the three the panels describe as setting quickly. Robinia — the honey sold as acacia — has the highest ratio in the set at 1.61, and chestnut is next at 1.48; both set slowly. The middle is where the ratio stops being enough on its own: lime, citrus, heather and thyme run from about 1.2 to 1.4 and all set at a moderate pace, because water content, the minor sugars and the particles that seed crystals all contribute.

The minor sugars are the informative ones

The 5 to 10 per cent that is neither fructose nor glucose barely affects how honey tastes, and tells an analyst a great deal. More than twenty minor sugars have been identified across the world's honeys, and several are specific enough to work as markers.

1. 1Melezitose says honeydewA three-sugar molecule produced by aphids rather than plants. Fir and some pine honeydew honeys carry enough of it to set in the comb — the beekeeper's 'cement honey', which will not extract and has to be pressed or left for the bees.
2. 2Trehalulose says stingless beeReported as a major sugar in some stingless bee honeys and only in traces in honey from Apis. Because the same flora yields ordinary profiles when worked by honey bees, the difference points at the bee's own metabolism rather than the nectar.
3. 3Raffinose and maltotriose say plant familyThe oligosaccharide fingerprint varies enough between floral sources to contribute to botanical authentication, though rarely on its own.

Sugar is still sugar