Why doesn’t honey go off?
Asked by: Terry Priest, West Sussex
Honey can last for thousands of years in sealed pots – it’s even been discovered in Ancient Egyptian tombs. The secret to its long life lies in the bees’ honey-making process.
Forager bees collect sugary nectar from flowers and transport it back to the hive. Here, the bees transfer the nectar to other worker bees, which repeatedly drink and regurgitate the liquid, reducing its water content. During this process, an enzyme in the bees’ stomachs breaks down the nectar’s glucose into gluconic acid – which helps to make honey acidic (pH of around 4) – and hydrogen peroxide.
Once the nectar is deposited in the honeycomb, the bees fan it furiously with their wings to speed up the water’s evaporation. The honey’s low water content and high acidity are the two main reasons it doesn’t spoil – the bacteria that cause food to go off can’t thrive in these conditions. The hydrogen peroxide also has antibacterial properties. So the honey stays fresh for the bees during the cold winter months – and for much longer inside our jars.
Dr Emma Davies is a science writer and editor with a PhD in food chemistry from the University of Leeds. She writes about all aspects of chemistry, from food and the environment to toxicology and regulatory science.
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