Tragedy of Forager Bees - Chemistry in Honey
This is a documentary shot by a bee lover, to record the sacrifice of a bee.
Haha, don't take it serious! Enjoy the video!
Tragedy of Forager Bees
Forager bees are responsible for harvesting nectar from flowers and transfer it back to the hive. However, due to natural occuring ethanol fermentation, sugars in nectar may ferment to form ethanol. Bees may be affected when consuming excess ethanol, they may die in flying accident or be punished by their fellows (chewing off its legs or force them to leave the hive) so that the drunk bees will not affect the norms of the hive community.
Ethanol fermentation
Glucose is commonly found in nectar, which may ferment under the reaction of yeast or other microorganisms. Below is the overall reaction which you probably know in secondary school Chemistry:
C6H12O6 → 2 C2H5OH + 2 CO2
Chemistry in honey
The forager bees will store the honey they harvested into a special stomach with enzyme. Sucrose in nectar is then digested by hydrolysis.
Sucrose + water → fructose + glucose
C12H22O11 + H2O → C6H12O6 + C6H12O6
It is then passed to house bees who re-drinks the nectar to further digest the large sugar molecules to monosaccarides.
Finally deposit it to honeycomb. When water evaporates, it will be found as raw honey!
Normally honey won't spoil because of its low water content (it dehydrates bacteria by drawing water away from the cell).
Also, bees secrete gluconic acid which is a dominant acid in honey giving it a low pH of between 3 and 4 to inhibit bacterial growth.
Question:
Why does bee secrete gluconic acid into honey? What is the reaction involved?
Hint: The molecule on the left is D-Glucose and the one on the right is D-Gluconic acid.
*under the reaction of glucose oxidase, glucose can be oxidized to carboxylic acid
However, honey is hygroscopic. When unsealed and exposed to air, it absorbs moisture from the air, thus it no long holds low water content environment.
Yeast may be able to grow and carry out ethanol fermentation may cause honey to spoil.
1. Ethanol fermentation (glucose → ethanol)
2. In presence of oxygen, ethanol → acetic acid (vinegar) + water
Spoiled honey give unpleasant flavours and several observable physical changes.
Gas bubbles are produced by yeast as they grow in sugar solution.
The bubbles make the dextrose sugar crystals visible by pushing them away from sugar solution (See the light areas which are the sugar crystals).
So when next time you observe gas bubbles or special smell in honey, you must watch out!
For further information, you may check it out here:)