How do bees turn nectar into honey?
Honey has some amazing health and keeping qualities that have been specifically created by the bees. So how do they do it?
In a nutshell (well, in a honey comb), they collect nectar, add enzymes which change it chemically, and remove excess water, then store it in honey comb. That sounds easy, right?
Let's look at the steps that happen on the way to the finished product:
Plants produce nectar
Plants produce nectar, using photosynthesis. The nectar is stored in nectaries, the bit deep inside the flower usually.
This nectar is mostly sucrose and water, with a few added goodies.
Foraging bees collect nectar
Worker honey bees spend the first half of their lives inside a hive, and the 2nd half of their lives as foragers.
A forager will fly out and gather pollen and nectar. To collect nectar, they suck it into their mouth parts called a proboscis. They can reach deep into long tube shaped petals if required, although flatter flowers are obviously easier.
Bees are 'species constant', meaning a particular bee will visit flowers of the same species on any given foraging trip. This also helps the plants, as the bee will be pollinating between flowers of the same species. So, gardeners - mass planting for the bees please!
The nectar is held in a special sac in front of the bee's stomach. Usually a bee will collect up to 40mg, which is about the size of a large raindrop (just think about this in relation to the size of a bee!). A bee may need to visit up to 500 flowers to get one full crop load.
Bees add enzymes
The foraging bee will add chemicals from her glands in her head.
One of these is invertase. This starts the reaction of turning sucrose into fructose and glucose, or 'inverting' the nectar. This will make the resulting honey easier to digest when they come to eat the honey - we know, for instance, that glucose is an easy, instant energy food. Same thing with the bees.
Nectar is brought back to the hive
The foraging bee returns to the colony. On arrival she will pass over her sacful of nectar to the processing bees. They pass the honey from mouth to mouth. Depending on how busy they are, one foraging bee might pass to many or a few waiting bees.
If she has found an amazing source of nectar she will do a bee dance to let the others know where to go to collect nectar too, so the whole hive can benefit. No individualism going on here, or bonus schemes for good workers, they all share.
The processing bees add more enzymes to the nectar, to continue the chemical reactions required to produce honey. Another of these enzymes is glucose oxidase. This turns the glucose into gluconic acid, which lowers the pH, which helps protect the honey from fermenting while it is still high in water.
Honey ripening begins with evaporation
The hive bees take the nectar and start the ripening process.
Cliff van Eaton, in his excellent book "Manuka, the biography of an extraordinary honey" describes it like this (on page 39): - but this applies to all honey, not just manuka
"Each processor pumps a bit of nectar out of her honey sac, and suspends it as a flat drop on the underside of her proboscis. In so doing, a large surface area of the liquid is exposed to the air....This process is repeated rapidly for 15-20 minutes, and as a result the contents of the honey sac loses approximately half of its water. The moisture content is now between 30% and 50%"
The bees then pack the honey into cells. The cells slope upwards at about 9 degrees so the nectar does not run out when it is still liquid. How clever is that?! They have thought of everything.
Stage 2 evaporation
At this point the nectar has lost a lot of water from being suspended in the bees mouth, but is still too moist to keep.
The next process is to evaporate the rest of the excess water, till the honey reaches about 18 - 20% moisture.
The hive bees initially put a little half ripened honey on each hexagonal cell wall, only partly filling the cells. As it dries out, the bees move it around to fill about 3/4 of a cell each.
While this is happening, the beehive turns into a giant dehumidifier. The bees all form long chains, inside the hive, and fan their wings. This circulates the warm air through the hive and helps evaporate the excess moisture. This happens best at night when the ambient humidity is lower, allowing more water to evaporate.
Packing the honey in cells
Once the honey is fully ripe and at about 18% moisture content, the bees pack it into another cell, and fill it up.
The cells are then closed off with a wax capping, effectively putting a lid on the honey jar so it will not reabsorb moisture from the environment.
If the honey is either not low enough in moisture to start with, or reabsorbs water, it will then start to ferment. And the fermentation will create alcohol, which is toxic to bees.
All this produces honey that has some remarkable qualities:
- it is high in sugar content
- the sugar has been inverted and is easy to digest
- it has low pH i.e. is acidic, which helps it keep and inhibits the growth of micro organisms
- the enzymes also assist with the hydrogen peroxide factor, which is an antibacterial effect present in all honey (not just manuka - which has a special extra feature from MGO) and is a whole other blog post topic
The whole chemical process
So here is the whole chemical process:
- enzymes are added by the bees, including invertase, and glucose oxidase
- the pH is lowered from acids in the bees' stomach
- water is evaporated
- sucrose in the nectar changes to simple sugars of glucose and fructose
- the honey cell is capped off to keep it at it's ideal constituency.
Well, that is a miracle for sure!