Why doesn’t honey go bad?

This article was reviewed by Pa Li Ze, chief physician of nutrition, member of the Science Popularization Committee of the Chinese Nutrition Society

Archaeologists have discovered ancient honey in Egyptian tombs, and it is edible.

The reason why honey can be stored for such a long time without spoiling is that bees repeatedly perform a series of dehydration actions in the process of collecting and producing honey. In addition, there are some enzymes in honey that can convert disaccharides into monosaccharides and then into acids, which helps honey to form a higher sugar concentration that is not easy to crystallize, and a pH value that is low enough to be unfavorable for the survival of microorganisms, making it difficult to spoil.

The gradual rise of modern beekeeping originated from people's discovery of the usefulness of honey thousands of years ago and the long-standing desire of mankind to collect large amounts of honey.

Cave paintings in Spain dating back 8,000 years have been found depicting humans gathering honey from wild bee colonies. Notably, they did so without the protection of beekeeping suits, suggesting that even in ancient times, honey was irresistible.

What exactly is this sweet, golden liquid, and how do bees make it?

As the name suggests, the production of honey is a characteristic of the species of bees we call honey bees (genus Apis). Some of their close relatives, such as wheat bees and bumble bees, also make a honey-like substance. However, pure honey from honey bees has a remarkable characteristic: it never goes bad.

"Honey is hygroscopic, meaning it can absorb moisture from the air," said Lewis Bartlett, a postdoctoral fellow at the University of Georgia who studies honey bee disease and evolution. "But when the water content increases to a level suitable for yeast growth, it causes the honey to ferment and become smelly." The natural process by which bees produce honey reduces the water content of the honey so much that no microorganisms (including yeast) can survive in the honey long enough to spoil it. As long as the honey is sealed, it can remain delicious forever - which explains why scientists found edible honey in dry ancient Egyptian tombs!

Several factors contribute to honey's unique and delicious chemical makeup. Honey is made from nectar collected from flowers by worker bees, and its main components are sucrose, glucose, and fructose. Once the nectar is brought back to the hive, the bees pass it back and forth between each other's mouths, a process called trophallaxis, which helps reduce the water content.

The worker bees then store the soon-to-be-made honey in the hive's storage chambers, where the high temperatures cause further evaporation of water. Once the water content is low enough, the bees cover the honey with beeswax. "The whole process is very fast, probably less than a week, but it also depends on the biological processes in the colony," Bartlett said.

When it comes to biological processes within the hive, the bees themselves affect the chemical composition of honey in many ways. Bee digestion can break down the sucrose in nectar into glucose and fructose. If it stays at this stage, it will create the best food source for microorganisms such as yeast, which is not conducive to the storage of honey.

But in this case, both because the water content of honey is so low that it limits the growth and reproduction of these microorganisms, and because the bees add an enzyme to the honey that fights microorganisms: glucose oxidase. This enzyme promotes the oxidation of glucose to produce hydrogen peroxide, a compound with powerful antibacterial properties.

All in all, bees use a combination of biochemistry and behavior to turn nectar into honey. But why do they do this? It turns out that bees love honey for the same reasons we do: it’s a long-term food source rich in sugars. With no flowers to forage for in the winter and the weather too cold for them to fly, they need lots of honey to help their colonies survive the winter.

Some beekeepers try to do some of the honey production for the bees, and sometimes this is necessary. For example, when the weather is too humid, the bees may have difficulty reducing the water content of the honey, so beekeepers will remove the honey and try to evaporate the remaining water themselves. However, some people think that the resulting honey is less than perfect. "I don't like it very much," Bartlett said. "I think the taste is different."

Climate change will alter global temperature and humidity levels, making it harder for bees and beekeepers to make the honey they all love.

But given the development of beekeeping from the days of Spanish cave paintings 8,000 years ago to the present day, there is good reason to believe that human ingenuity and action on climate change will produce a solution as sweet as honey.

Source: Science Circle (ID: keyanquan), Discover Magazine

Written by Darren Incorvaia, translated by Yiqing

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