From nectar to honey
PHOTO: G. KARTHIKEYAN
How do bees convert nectar from flowers into honey?
KRISHNAMOORTHY
Warangal, Andhra Pradesh
The conversion of nectar in to honey by honeybees involves both physical and chemical changes. Nectar obtained from the flowers by bees is composed primarily of the disaccharide sugar, sucrose, and the monosaccharide sugars, glucose and fructose.
The concentration and composition of these sugars in the nectar vary from plant species to species. Other constituents that have been identified in nectars include amino acids, vitamins, secondary metabolites such as alkaloids and flavonoids and even some minerals. The taste and colour of honey is affected by all these constituents in the nectar.
Honey bees collect the nectar from flowers and deposit it in the hives where it is converted to honey. This process involves converting the disaccharide sucrose into its monosaccharide sugars, glucose and fructose and part of the glucose into gluconic acid (chemical changes) and reducing the water content of the nectar (which ranges from 30 – 90 per cent) to about 18 per cent (physical change).
Bees produce an enzyme (invertase) that converts sucrose into glucose and fructose. Part of the glucose is converted to gluconic acid and hydrogen peroxide by another enzyme (glucose oxidase). Gluconic acid reduces the pH of honey to the acidic range and makes it inhospitable for microbes. Hydrogen peroxide might also provide temporary protection against certain microbes.
Water content in the nectar is reduced by evaporation. Bees achieve this by placing small droplets of the nectar in the cells of the hive and fanning with their wings for air flow. The high osmotic nature (low available water content) of honey also helps inhibit the growth of microbes.
SENTHIL SUBRAMANIAN
www.knowplants.org
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