How do bees turn nectar into delicious honey?

Since my first article in this mini-series on honey, food fraud history has been made in Zealand this month with the prosecution of Auckland based company Evergreen Life Ltd. Food Safety Standards uncovered 64 counts of fraud which included manuka honey adulteration involving the addition of synthetic chemicals, including one normally used in sun tanning lotion. Such criminality like this, involving Evergreen Life and other companies, accounts for why far more manuka honey is sold than actually produced naturally by bees.

“How do honey bees make honey naturally?” you may be wondering. Well, firstly, bees collect nectar from attractive plants that lure them to their petals and nectaries with delicious perfumes, sweet nectar and bright colours. Many plants have nectar guides incorporated into the flower structure and some of these are easily seen by humans. Foxglove with its blotchy petals is a good example. However, some nectar guides utilise ultra violet light, invisible to human eyes, but, since the bees have eyes sensitive to ultraviolet light, they can see the strongly reflected light from dandelions. To us the dandelion appears all yellow but to the honey bee the outer ring of florets appears purple and a patch of dandelion looks to a bee like bull’s eyes on a dartboard.

Did you know that honey bees and human beings are the only two species whose members can communicate to one another the location of important resources, such as excellent sources of food? We do this whenever we guide friends to an outstanding restaurant by giving them driving directions. Honey bees do this when they steer their hive mates to rich flower patches by performing waggle dances. Like the Vikings, who used the sun, moon and stars to navigate across the oceans, honey bees also use the sun as a compass. And like the Vikings, bees are aware of the sun’s position changing throughout the day. Honey bees know where the sun is even when inside their dark hives because their eyes recognise polarised light with its intensity and vibrations that depend upon the position of the sun. Since they do not fly after dark, bees have no need to use the moon and stars for navigation.

The waggle dance was first discovered and decoded by Karl von Frisch, a distinguished professor of zoology at the University of Munich around 1914. However, it wasn’t until the summer of 1944 that von Frisch learned that the information communicated by the dance was more than just a message about the type of flowers worth visiting based on sharing floral scents during the dance, but it was also about providing directions to the flowers. He would go on to receive the Nobel Prize for his pioneering work, paving the way for future scientists to study further the waggle dance and to learn how bees also indicate distance to the food source, during the dance, by timing the duration of the waggle phase.

The Waggle Dance and How Bees Find Food Source. Illustration reproduced by kind permission of Professor Tom Seeley

The top part of the picture shows a bee performing a figure of eight dance and waggling its abdomen at a 40˚ angle from the dotted line which depicts the sun’s direction. You can see the other bees attending to the dance and these are the new recruits that will go off to the flower patch and assist with nectar collection. The middle part shows the relationship between the duration of the waggle dance and the distance to the food source. So, if the waggle movement lasts as long as 4 seconds the food source is 5000m/5km/3 miles away.

The lower part reveals the flower source which is at a 40 ˚ angle from the sun.

Honey bee tongues are part of a sophisticated apparatus called the proboscis, comprising several parts which work together like a straw through which nectar is sucked. The proboscis neatly folds away when not in use. Nectar is swallowed and carried in the oesophagus to a flexible, expandable sac called the honey crop, which is attached by a valve to the intestinal tract.

On return to the hive with an average sized 32mg load of nectar, the forager looks around for a house bee to unload the nectar. She accepts the regurgitated liquid and packs it into the cells in the honeycomb, which is held in place by wooden frames made up by the beekeeper for honey storage. The forager then returns to the same flower patch for as long as nectar is being produced there. During the homeward flights, the process of converting nectar to honey starts with the addition of enzymes from hypopharyngeal glands located in the head. Invertase is the enzyme involved in the chemical process of converting the disaccharide sugar sucrose to the monosaccharide sugars fructose and glucose.

Back in the hive, the house bees continue to process the nectar, turning it into honey by evaporating much of the water. This is done by rolling drops of nectar around at the end of the proboscis and also by the fanning of many wings inside the hive and at the hive entrance to move air into the hive and direct moisture- laden air to the outside.

House Bees Packing Nectar into Cells. Photo by Jim Boogaerts

Nectar is a watery solution containing many dissolved substances. The sugar content varies according to the plant species, environment and weather conditions, but the ratio of the average nectar is 80% water/20% sugar and when it becomes honey the water content must be below 19%, in most honeys, so that fermentation will not occur. Various sugars are contained in nectar along with: vitamins; amino acids; minerals; organic acids; pigments; aromatic compounds; antioxidants; and occasionally lipids and proteins.

An astounding 120 kg nectar is needed by the average colony yearly to provide food for brood and adults and to supply energy for keeping the brood nest at a constant temperature. Nectar is crucial for delivering the energy needed to power wing muscles for foraging flights.

When nectar has been converted into honey it is stored in hexagonal wax cells and capped with wax to preserve it and prevent moisture from fermenting the honey. Honey is described as being hygroscopic which means that it attracts moisture and is the reason why honey pots with lids to accommodate spoons are not great storage containers because they are not airtight.

Honey can be stored for years inside the sealed cell and the perfectly preserved honey found in the tombs of the ancient Egyptians bears testimony to the antibacterial properties of honey. Hydrogen peroxide is just one of the ingredients which contributes to honey being a low risk food. However, our food regulations demand that producers give a best before date of about 3 years on a jar of honey for sale in the UK.

A Perfect Honey Comb. Photo by Jim Boogaerts

Putting the Finishing Touches to Capping Honey Cells. Photo by Jim Boogaerts