How Do Bees Make Honey?

The Production of Honey in Four levels

Bees collect nectar from flowers and store it in their honey stomach (“crop”). Enzymes within the crop break down large sugar molecules into simpler structures (glucose and fructose). In honey bees, the forager returns to her hive and regurgitates this partially-processed nectar to a nectar-receiving bee, who continues the conversion process by adding more enzymes. The now processed-nectar is ripened to evaporate excess water and capped with a layer of wax. This capped honey is extracted by the beekeeper or eaten as whole comb.

I’m doing it differently here and explaining the honey production process in four levels of complexity, child, teen, beekeeper and a detailed explanation (complete with equations and all) as the Bee Brofessor™.

There’s a shirt that goes with this article – designed & pressed by Yours Truly.

Child: Bees Make Honey From Flowers

When a bee finds a flower, she goes to where the sugary drink called nectar is made. They use their long tongue to suck up the sweet juice and store it in their special honey stomach. Bees have two stomachs, one for honey, and one for everything else. As they carry the nectar back to their hive, they share it with other bees who chew and mix it with their spit. The spit makes the nectar thicker and is added in until it turns into honey. This honey is added into little cups of beeswax inside their home, where bees begin fanning their wings to make it even thicker.

When the bees think it’s ready, they cover it up with more wax to keep it safe from water and other insects. Now it is ready to eat – either in big bites as honey comb, or by removing the liquid honey from the cups and putting it into jars.

Teen: Honey is How Bees Store Food for Later

All bees make honey. Honey bees make it in large amounts as food for their colony. First, a worker bees visit flowers to collect nectar using a specialised tongue known as the proboscis. The nectar is stored in their crop, a special stomach that produces enzymes that process the nectar. Back at the hive, they regurgitate the nectar to other worker bees, who in turn pass it to other bees. These bees add enzymes from their crop and digestive tract to break down the complex sugars into simpler ones like glucose and fructose. This process also prevents the honey from spoiling.

Eventually, the partially digested nectar is deposited into hexagonal wax cells, where bees fan it with their wings to evaporate excess water. The removal of water concentrates the nectar, making it thicker and less likely to spoil. Once the water content is low enough (around 18%), the substance is officially honey, and the bees seal the cell with wax for storage.

Beekeeper: Honey is the Ripening of Foraged Nectar

Honey making begins with the forager bee collecting nectar from flowers. Nectar is a sugary liquid secreted by flowers to attract pollinators, who (usually) pollinate the plant as they wander within. Foragers use their proboscis to draw the nectar into their honey crop, a second stomach for storing and processing liquids in place of digestion.

Once back at the hive, the forager regurgitates her nectar to a nectar-receiving middle-aged worker bee (“trophallaxis”). The exchange of nectar mixes it with enzymes that process the nectar into more a digestible form. One such enzyme is invertase, which breaks down sucrose into glucose and fructose, and is found in the salivary glands of worker bees.

After several rounds of trophallaxis, the nectar-processing bee deposits this partially-processed nectar into a wax cell. At this point, the nectar is still quite watery, with a moisture content of around 70%. To reduce this moisture and thicken the nectar into honey, workers fan their wings to create airflow over the comb and accelerate evaporation. You can smell this process at dusk by standing next to your hives after a day of good forage.

As the nectar thickens and reaches a moisture content of ~18%, the bees cover the cell with a cap of wax to protect it until its needed. This final product is what we call honey. A low moisture content ensures stability and reduces the chances of spoilage via fermentation, as bacteria cannot survive under such low-water, high-sugar conditions.

At this stage, you can begin harvesting the capped honeycomb (and some of the less-capped ones, because we’re all human). Be sure to leave enough for the bees in the event of sudden dearth, poor foraging conditions, or if this is your final harvest prior to overwintering. Sugar concentrations vary between flower species, as do the micronutrient compounds.

Bee Brofessor™: Honey is the Physical and Chemical Processing of Nectar

In eusocial insects like Apis mellifera, the eldest bees take on foraging duties to collect floral nectar. Nectar is an aqueous solution of sugars (primarily sucrose), secondary metabolites (alkaloids – nicotine, coffee, flavonoids, terpenoids and more), vitamins and minerals. Nectar composition varies depending on the plant species, and it is secreted to reward ongoing plant-pollinator relationships.

As the worker lands on the plant to access the nectary, she may be coated in pollen from the anthers. A. mellifera shows flower specificity, and she will continue collecting nectar from the same plant species, resulting in the transfer of pollen between different flowers. Of course, some workers may choose to keep the pollen for the hive and pack it into their hind legs’ corbiculae.

Foragers use their proboscis to extract nectar and store it in their honey crop, a specialised transport organ distinct from their digestive stomach, to transport the nectar to the hive. As she flies home, the nectar is subjected to enzymatic activity. Most of the activity is conducted by the invertase secreted by the bee’s salivary glands. This protein hydrolyses sucrose into its monosaccharide components, glucose and fructose, initiating the conversion of nectar into honey.

Upon arrival at the hive, the forager regurgitates the partially processed nectar and transfers it to nectar-receiving bees via trophallaxis. During this exchange:

• Additional invertase is provided to further convert sucrose into fructose and glucose,
• Proteases break down the proteins and polypeptides into smaller forms, and
• Diastases degrade the larger starch and dextrin sugars into smaller carbohydrates, amongst others.

The nectar-processing bees continue this ripening process over several days, further manipulating the nectar with their mandibles and mixing it with additional enzymes to reduce its water content.

Moisture reduction is achieved through fanning. Bees fan their wings in synchronised patterns to create airflow and drive water loss. The initial ~70% water content, is reduced to approximately 18%, resulting a highly concentrated sugar solution resistant to fermentation and microbial spoilage.  Once the moisture content is stable, the honey is capped with wax to protect it honey from environmental moisture and contaminants, preserving it for future colony needs.

The viscosity and low water activity of honey are key to its long-term stability. Honey’s low water activity makes it difficult for many microorganisms to establish themselves. Paired with a high sugar content, it creates a hyperosmotic environment whereby water is drawn out of microbial cells via osmosis, desiccating the organism. A low pH along with the production of gluconic acid and hydrogen peroxide furthers the antimicrobial activity as it damages cell walls and organelles.

First Step: Converting Complex Sugars into Simple Sugars

Enzymatic hydrolysis is how larger sugars (sucrose and maltose) are broken down into glucose and fructose by diastase and invertase enzyme activity (reviewed in Alaerjani et al., 2022). invertase breaks down sucrose at its glycosidic bond (i.e. bonds to a sugar molecule), resulting in the formation of glucose and fructose. This is a two-step process:

1. Glycosylation, whereby the enzyme cleaves the carbon bond into glucose and an enzyme-fructose intermediate.
2. Deglycosylation, whereby a water molecule is added to the intermediate, releasing the fructose and regenerating invertase to start another reaction cycle.

Depending on the nectar source, the resulting product ends up with “the typical sugar composition of honey”: 30–40% fructose and 25–35% glucose. Fructose is the sweeter tasting of the two, and is less likely to crystalise than glucose. A high fructose:glucose honey is therefore sweeter and will remain liquid for a longer period than one with the opposite ratios.

Why Can’t Honey be Made with Complex Sugars?

What if honey was produced with sucrose or larger sugar molecules? Monosaccharides have a lower risk of microbial degradation than sucrose as their presence creates an antimicrobial environment.

Sucrose is a larger molecule made up of one glucose molecule and one fructose molecule, and microorganisms can break this bond using enzymes like sucrase (one of the most common enzymes around – after all, sugars are pure, raw energy!). On their own, glucose and fructose are directly absorbed and metabolised, however there is an additive effect from having high concentrations in the honey.

This “hyperosmotic environment” leads to low “water activity” – a value for measuring the water availability in a substance – and prevents many microbes from accessing the necessary water for growth. Sucrose’s larger molecular size makes it less effective at lowering water activity compared to an equivalent mass of simpler sugars because it dissociates into fewer molecules when dissolved in a solution. In other words, adding 100 grams of sucrose and 100 grams of glucose/fructose into a liquid would result in more of the latter being dissolved than the former.

Further, acidic conditions are created by gluconic acid as glucose is broken down by glucose oxidase. This enzyme also produces hydrogen peroxide, another antimicrobial agent. Sucrose does not interact with glucose oxidase, nor does it have its own “sucrose oxidase” analogue. Thus, the simple sugar glucose indirectly contributes to honey’s antimicrobial activity.

You can obtain honey containing complex sugars if you harvest frames of uncapped honey. The product would be closer to nectar than what we can legally call “honey”, and you’ll see that it tastes faint, crystalises faster and develops odd tastings after a while. My first “harvest” was like this, I was impatient and wanted to show off to the family, and so I gifted them this uncapped “honey” that went bad after a month… mistakes were made.

Fructose Contributes to Honey’s Antimicrobial Defence by Reducing Water Availability

Fructose is more soluble than glucose (and most other sugars) due to the multiple hydroxyl (-OH) groups within it. If you recall chemistry class, hydroxyls form strong hydrogen bonds with water molecules, leading to a “hydration shell” whereby water is strongly bound to fructose, reducing the available water (“water activity” mentioned above). Further, the ketone group in its structure promotes its existence in its cyclical isomer- this exposes multiple hydroxyl groups to the surface and forms more hydrogen bonds with water molecules (for technical reading, see Dholariya & Orrcik, 2022).

Second Step: Converting Glucose to Gluconic Acid and H₂O₂ by Glucose Oxidase

Glucose oxidase is secreted from the worker bee’s hypopharyngeal glands and catalyses the reaction to form gluconic acid and hydrogen peroxide from glucose and water.

The enzyme binds glucose to glucose oxidises its aldehyde group (-CHO) into a carboxylic acid (-COOH), forming gluconic acid. The electrons removed during oxidation are transferred to molecular oxygen, producing hydrogen peroxide¹.

Gluconic acid is the largest contributor to the acidity of honey. Other organic acids (acetic acid, formic acid, citric acid etc..) are present in low quantities as their concentrations depend on the floral source. Hydrogen peroxide disrupts microbial cell walls and organelles. Heard about honey in wound healing? It’s hydrogen peroxide in action.

Use of Honey in Wound Healing: Hydrogen Peroxide 

Recall the formation of gluconic acid above. In concentrated honey, hydrogen peroxide production is limited due to low water activity. When honey is diluted by fluid (e.g. wound exudate), glucose oxidase becomes more active, producing gluconic acid to reduce microbial growth at the wound site, and hydrogen peroxide to damage existing microbes². The compound damages microbial cell walls, proteins, and DNA through the generation of reactive oxygen species, and has broad-spectrum antimicrobial activity (reviewed in Tashkandi, 2021).

The low-level oxidative stress induced can stimulate wound repair (our bodies grow by being broken and rebuilt). The controlled release of oxygen free radical stimulates fibroblasts and keratinocytes for tissue repair and wound closure and promotes the formation of new blood vessels (“angiogenesis”) to enhance oxygen and nutrient delivery to the wound site.

Would you use honey in lieu of modern medicine on a wound? Probably not. If you’re in the middle of a forest and honey is all you’ve got? Well, it’s better than nothing.

 &

Non-Enzymatic Reactions: Hydroxymethylfurfural, Methylglyoxal

There are other, non-enzyme mediate reactions that take place in honey. An exhaustive description is too great, and I conclude this post with five examples. It is these reactions that give honey its individual taste profiles.

• The Maillard reaction is a non-enzymatic browning between the sugars (glucose and fructose) and amino acids or proteins in honey. These are flavour compounds and contribute to the darkening of honey over time, or when it is exposed to heat (“caramlisation”).

• When high concentrations of sugars are exposed to oxygen, they undergo autoxidation (self-oxidation), forming various acids and carbonyl compound. The acid production contributes to taste and antimicrobial resistance (recall the other organic acids mentioned above), as well as flavour
• Hydroxymethylfurfural (HMF) is a compound formed through the dehydration of sugars and is a marker of honey quality- the higher the concentration, the more likely it’s adulterated or (poorly-stored) old honey.

• Redox reactions take place between the various phenolic acids and flavonoids derived from nectar and pollen. These are thought to give honey its antioxidant capacity and you guessed it… contribute to taste.

• Organic phosphates like ATP or phosphate esters break down into simpler phosphates, whereas polysaccharides like amylose are also broken into simpler sugars through hydrolysis. More simple sugars means more gluconic acid and water-binding properties (fructose).

“Four Levels of Honey Production”

I tried a new approach; how’d you find it? I enjoyed it, so I’ll attempt another concept in the same manner. I also toy with the idea of writing in “zoomer brainrot” on the hopes of reaching a larger audience of sigmas…. Perhaps that’s best left to a visual medium…. Gen Z is not known for their literacy skills.

Read the whole post and found puns, typos mistakes? Voice your displeasure with a strongly-worded message to admin@tgbee.com.au, or by filling this form.

Postscript: What about Manuka Honey???

I didn’t want to write about manuka because… it’s manuka, the Donald Trump of honey- everyone talks about manuka this, manuka that, manuka priced like this. And hey, like Trump, it may be good for you. Here’s my friend Chad Jippe Tee’s take on Manuka:

Manuka differs from regular honey because it does not rely on hydrogen peroxide to exhibit antimicrobial activity. Methylglyoxal (MGO) is formed from the natural conversion of dihydroxyacetone (DHA) in the nectar of Leptospermum (tea trees), and when honey is made using this nectar, it has higher levels of DHA and thus MGO. The “unique manuka factor” (UMF) is a measure of the MGO content, hydrogen peroxide activity and other bioactive components in the product you’re buying.

Footnotes

1. For those wondering, oxygen (O2) has an infinite supply. Forming carboxylic acid from an aldehyde group involves the addition of oxygen (from -CHO to COOH) to glucose. Two electrons are transferred to the O2, producing O2 with a 2- configuration (peroxide). At this point, the negatively charged peroxide ion interacts with two protons (hydrogen ions, H+) to form hydrogen peroxide. The protons are found freely in the aqueous solution that is nectar. The addition of two protons neutralises the negative charge, resulting in electrically-neutral hydrogen peroxide. ↩︎
2. The hydrogen peroxide in commercial formulations is at a higher concentration is harmful to all cells. In honey, the controlled production of the compound by glucose oxidase releases it​ slowly and at low concentrations, limiting its cytotoxic effects on healthy tissue, but ensuring antimicrobial activity. ↩︎