The following factors have a main influence on the crystallization behaviour of honey:
- sugar spectrum
- water content
- storage temperature
- duration of storage
- presence of crystallization nuclei
- various measures of the honey processing
The starting point for the crystallization of honey are so-called crystal nuclei, microscopically small particles such as tiny glucose crystals, pollen grains, dust particles or air bubbles. The primary crystals grow by attaching further glucose crystals to them.
Tab. 1: Factors influencing crystallization [2]
|
|
no crystallization |
rapid crystallization |
|
glucose/water ratio |
< 1,70 | > 2,16 |
|
fructose/glucose ratio |
> 1,33 |
< 1,11 |
|
(glucose-water)/fructose ratio |
< 0,30 |
> 0,49 |
|
% glucose |
< 27,7 |
> 35 |
|
coeffizient of supersaturation on glucose |
< 1,8 |
> 2,6 |
Honey with high fructose content crystallizes slowly, whereas honey with high glucose content crystallizes quickly.
Processing
Honeys that do not remain liquid for a long time should be specifically crystallized. In the case of fast crystallizing honeys this can be reached by stirring. In the case of very slowly crystallizing honeys these honeys should be inoculated with a fine crystalline honey (approx. 5 – 10%), afterwards the honey is stirred until a fine crystalline, spreadable consistency is present.
If the honey is to remain liquid, it is recommended to clarify it. For this the honey is left at room temperature so that wax particles and air bubbles, which could function as crystallization nuclei, are separated at the surface.
When mixing the honey afterwards this should be done carefully so that no air bubbles get into the honey.
Storage
Low storage temperatures have an inhibiting effect on crystallization, as the increased viscosity of the honey reduces the diffusion rate of the molecules. At higher temperatures honey crystallizes forming coarse crystals. According to Dyce [1], honeys crystallize the fastest at a constant temperature of 14 °C.
Tab. 2: Influence of temperature on crystallization
|
< 4°C |
high viscosity, low crystallization tendency |
|
5 – 7 °C |
Primary crystals form preferably |
|
14 °C |
optimum growth of crystals |
|
> 30 °C |
crystals melt |
Before storing liquid honeys, they should be heated to melt all existing crystals. If immediately followed by rapid cooling to 0 °C and storage at 0 °C for 5 weeks, the honey can remain liquid for up to 2 years if subsequently stored at 14 °C. Honey which is stored directly at 14 °C without a previous cooler storage will be crystallized within 5 weeks. [3]
When the honey is heated, this must be done carefully in order to not heat the honey to such an extent that the natural enzymes have been either destroyed or significantly inactivated. If this is the case the honey, with the exception of baker´s honey, would no longer comply with the provisions of the Council Directive 2001/110/EC relating to honey.
[1] Dyce, E.J.: Crystallization of honey. J. econ. Ent. 24, 597-602 (1931b) und Dyce, E.J.: Fermentation and crystallization of honey. Bull. Cornell agric. Exp. Sta. No. 528 (1931a)).
[2] Bhandari, B., D´Arcy, B., Kelly, C.: Rheology and crystallization of honey: present status. International Journal of food properties, 2 (3), 217-226 (1999)
[3] Austin, G.H.: Maintaining high quality in liquid and recrystallized honey. Can. BeeJournal 61 (1), 10-12, 20-23 (1953)