Saturday 22 October 2011

How do bees make Honey?

I was asked this question at Hanbury Hall last week. Here is a description of the work that the bees do to turn nectar into honey.

These bees are filling wax cells with honey, ready  for sealing like the cells at the top of the photo

The older worker bees (all girls because the boy bees don't do any work!) go out to collect nectar from flowers.  They suck the nectar into their stomach to transport it back to the hive.

As they suck the nectar up, it is mixed with an enzyme called invertase which is produced by a gland in their head.  It is a bit like the way that we mix the food we eat with saliva as we eat it.

Nectar is a sweet liquid produced by plants as a 'bribe' to get the bees to visit.  It varies in sugar content by plant from about 5% sugar up to about 70% sugar.  The majority of the rest of the nectar is water.

When the bee gets back to the hive, they 'unload' the nectar to the younger 'house bees'.  These bees are all female and they do all the work inside the hive, cleaning, feeding the larvae and processing the nectar into honey. 

The returning bee 'sicks up' the nectar from thier stomach and offers it to a house bee.  If the nectar is the sort needed, then the house bee will take some.  The returning bee then offers some nectar to another house bee, and so on until their stomach is empty.  When the weather is hot, bees need water to drink and to cool the hive.  In this case the house bees will prefer to take a more watery nectar, so returning bees with this sort of nectar will 'unload' quicker, so they know they have the right stuff, and will go back out to get more.  Because the house bees don't really want really sugary nectar in hot weather, returning bees with sugary nectar will find it harder to give it to the house bees, so they learn that they should try collecting something else!

Once the house bees have the nectar they have to 'process' it into honey.  There are two aspects to this, a chemical change in the sugars and a reduction of the water content.

Nectar generally contains a sugar called sucrose, which is a disaccharide.  Honey consists of a mixture of fructose and glucose, which are monosaccharides.  Converting from one to the other is a process called inverting, and is carried out by the enzyme, invertase, which the bee added to the nectar when it first sucked the nectar from the flower.  I won't bore you with any more details of this process.  If you want to know more then I recommend the books listed on the page.

The bees also need to reduce the water content in the nectar so that the resulting honey will remain fresh for a long time.  First of all, the house bees 'sick-up' a drop of honey which they manipulate with their proboscis (a sort of drinking straw sticking out of their mouth that they use to suck up nectar).  After a while they swallow the drop again and then do the same again.  While the drop is out of their stomach it can evaporate water, making it a more concentrated sugar solution.

When the house bee has made the nectar a bit more concentrated they will 'paint' the solution onto the inside of a wax cell, so that more water can evaporate.  They move this 'unripe honey' around from cell to cell as it gets more and more concentrated. 

Finally, when they have got the water content below about 20%, the nectar has become honey.  This is then moved from all the half filled cells that were being used for processing into a full cell of honey.  The bees then put a thin wax capping over the honey to protect it.  It will now last unchanged for years and years.