Known as nature’s sweetener, honey is adored worldwide for its golden tint and viscous consistency. Making honey actually involves a lot of chemistry; and far from being a man-made substance, it’s the bees that are the real chemists.
Now that spring has sprung, you may have noticed that our beloved bees are making their first 2018 appearance. Bees are integral parts of our planet and, by converting nectar into honey, one of nature’s most efficient chemists. But before we look at how they do this, we must first look at the composition of honey.
Honey is the result of complex chemical processes and it contains over 181 compounds. Chemically, it is a supersaturated solution because it contains more dissolved material (glucose and fructose) than the solvent (water) can dissolve.
Supersaturation is achieved by adding heat, enzymes or chemical agents to a solution. Because of this, honey has very low water content (15-18%) and this is why it is so viscous.
Before we get honey, nectar undergoes several chemical processes to be converted into a supersaturated solution. Unlike its gooey cousin, nectar is very thin with an 80% water content. Nectar is also less sweet because it is composed of different sugars.
Sugars in Nectar and Honey
Honey and nectar contain different sugars. Nectar is mostly composed of the complex sugar sucrose, which bees convert into simple sugars when making honey:
- Sucrose is mostly found in pure cane sugar. It is formed when 2 simple sugars are combined. This makes it a disaccharide. In nectar, sucrose is made up of fructose and glucose.
- Fructose and glucose are the simple sugars found in honey. As monosaccharides, they are each one sugar even though they have the same chemical formula (C6H12O6) – but that doesn’t mean they’re exactly the same. Fructose actually tastes sweeter than glucose because of the difference in their atomic arrangement.
Sucrose is more easily recognised as the table sugar in your kitchen. Comparatively, fructose is much sweeter and is also the dominant sugar in honey. This is why honey is a lot sweeter than normal table sugar.
How is Nectar Converted into Honey?
When bees collect nectar, they chemically change it by using enzymes to bring about supersaturation. In bees’ salivary glands, the enzyme invertase is produced. This is what the bees add to nectar to kick-start its transformation into honey.
Like all scientific processes, the bees’ method requires a collective effort and several precise steps. In a nutshell:
- Worker bees collect the nectar and store it in their honey stomach
- Bees add the enzyme invertase to the nectar as they carry it
- Invertase breaks down sucrose and converts it into fructose and glucose
- The worker bees transfer the nectar to the house bees, who add more enzymes to it
- House bees spend the next 20 minutes regurgitating and re-drinking the nectar. This breaks down the sugars even more by adding more enzymes to it
- The nectar is then deposited on the honeycomb
- The bees fan the deposited nectar with their wings to dry it out by encouraging evaporation
- When the water content is between 17-18%, the bees stop fanning it
- The resulting honey is then moved to a storage location
- Through evaporation and the use of enzymes, our buzzing chemists have creates a supersaturated solution
Use of Enzymes
Enzymes are important organic compounds that are produced by all living organisms. They help accelerate biochemical reactions and are crucial to all metabolic processes.
When bees make honey, there are several enzymes that they add:
- Invertase catalyses the hydrolysis of sucrose into simple sugars
- Amylase catalyses the breakdown of starch (amylose) into glucose
- Glucose oxidase is produced in the bees’ honey stomach and catalyses the oxidation of glucose into hydrogen peroxide and gluconic acid
- Catalase catalyses the decomposition of hydrogen peroxide into water and oxygen
Why Doesn’t Honey Go Bad?
The oldest sample of honey has been dated back to Ancient Egypt, with an approximate age stamp of 3,000 years – and it is still edible. So what keeps honey preserved for such a long time?
There are several factors that play into this sweet treat’s immortal powers. The combination of hydrogen peroxide, low water content, low water activity and an acidic pH provide a protective barrier against bacteria that will help honey last forever.
The presence of hydrogen peroxide adds an antimicrobial barrier to honey. This, as well as its soothing properties, is also why honey can be used to treat wounds.
Hydrogen peroxide is produced by the enzyme glucose oxidase, which is also known at Notatin. Glucose oxidase has proven antibacterial activity, and when coupled with hydrogen peroxide behaves as an effective defence against bacteria.
Low Water Content
With an average of only 17% water, honey has less water content than bacteria or fungi. Bacteria loves moisture because they need it for growth. Honey’s lack of water discourages bacterial growth because it creates a hostile environment.
Honey also has low water activity. This is a measurement of the amount of water needed to support microbial life. Measured on a scale of 0 – 1, bacteria are unable to grow on anything with a water activity below 0.75. It’s good to know, then, that honey’s water activity is around 0.6.
Despite its sweet taste, honey has a relatively acidic pH. This is because of the presence of gluconic acid, hydrogen peroxide, and other weak acids released during the chemical process. With an average pH of 4, this acidity also prevents against spoiling because bacteria prefer more neutral conditions.
When it comes to honey, there are just some things that nature does better. At ReAgent, we’re constantly looking into the science and chemistry behind everyday things. Why not sign up to our newsletter to keep updated on our latest findings? It’s free!