Honey produced by bees of the species Apis mellifera (the honey bee) can be derived from two distinct honey sources: nectar or honeydew. Nectar, which is usually the main source of honey, is the sweet liquid secreted by glands, known as nectar glands, found on many plants.
Honey plants and foraging bees
A large number of plant species produce nectar or pollen, but not all of them attract bees and are less interesting to a beekeeper. The beekeeping value of a plant depends on certain criteria: it must produce nectar or pollen that is attractive to bees, the nectar must be accessible (because of the depth of their corollas, the flowers of some plants, such as red clover, can only be visited by bees with long tongues), it must also become good honey, and finally, the plant must be common (the flowering area must be large enough).
The foragers collect the nectar and honeydew by adding their saliva, which is loaded with the enzyme invertase (or saccharase), which starts the transformation of sucrose into a mixture of glucose and levulose.
Back in the hive, they distribute their harvest to the other workers, who pass it on to each other several times by trophallaxis, in order to continue the transformation of sugars by the workers' saliva.
The workers then place the honey in the cells and take it back several times to help the water in it evaporate.
Maturation of nectar into honey
The ripening of nectar into honey consists of a transformation of sugars and a decrease in water content. On average it lasts from 2 to 5 days. It depends on several factors: the initial water content when the honey is stored in the cells, the amount of honey in the cells, the temperature and humidity of the air inside the hive, and the space available to the bees in the hive.
The characteristic sugars in mature honey are formed by various enzymatic reactions. Enzymes supplied in the saliva (in particular invertase) hydrolyse sucrose into glucose and fructose. An enzyme called glucose oxidase catalyses the oxidation of some glucose molecules into gluconic acid, which gives honey its acidity. During this reaction, hydrogen peroxide is also produced. The dehydration of the nectar during maturation is due to the fact that its hygroscopic degree is higher than that of the hive. The bees maintain a high temperature (close to 35°C) which reduces the humidity level.
This is followed by the passive water evaporation phase, which lasts 1 to 3 days, during which the bees ventilate the frames with rapid wing movements to bring the water content to about 18%, which is the ideal level. When the honey is mature and has reached a low moisture content, glucose oxidase becomes inactive and the product stabilises. The wax bees seal the honeycomb with a thin, airtight layer of wax, which allows the honey to be stored for a long time.
The honey in the hive can then be harvested by a beekeeper, while the bees keep their reserves for the winter.
