Name: Tom K.
When you put honey in the microwave, after the honey is
heated a then cooled the property's of the honey changes. Why does this
process happen? Dose this process happen in other things too?
Without knowing what properties you are speaking of, let me try to answer
your question. Microwaving honey should have not effect on honey that
heating it in another fashion would not have and any changes are a function
of the temperature to which you heat it.
Honey contains volatiles substance from the source nectar that give honey
its unique taste. These will be released from the honey as temperature
increases thereby changing the taste. Honey also contains enzymes produced
in the glands of the honey bee. These too are diminished by the heating.
Those who eat honey for its health benefits (as compared to just for
sweetness) find this unacceptable.
Much commercial honey is already heated to 160-180 degrees to discourage
crystallization. "Raw" honey is generally not heated above 100-120 degrees.
This temperature will reliquify crystallized honey.
When the bee stores honey, the hive is kept at a temperature in the mid
90's. That has lead some to consider the heating to 100 degrees to be only
a slight compromise on the "real" product.
If you are concerned about these changes, heat your honey gently, or
consider eating crystallized honey (creamed honey) or buying your honey in
Water is well heated by microwaves because it has lots of Hydrogen atoms bonded to Oxygen atoms.
The Hydrogen being relatively positive and the Oxygen being relatively negative,
there is a strong electric dipole moment for the electric field in the microwaves to yank on, to make heat.
Well, Honey is sugar and water, and sugar is mostly repeated (HCOH) groups, linked together between carbons.
So there are plenty of -O-H groups
to absorb microwaves and transfer their motion to the rest of the molecule.
If the honey has already grown some sugar crystals, they will first dissolve with just a little heating,
because more sugar can dissolve in hot water than in cold. That makes foggy honey clearer.
Being better dissolved, the honey may have lower viscosity and be slightly more pourable.
The next thing that happens to honey when it is heated is, it dries out a bit.
Loosing some of the water makes it a thicker liquid,
and eventually solid crystals of sugar will grow in the syrup.
Sugar is heavier than water, and the amount of sugar dissolved in water can be
characterized by measuring the specific gravity of the honey.
The dried out honey will be a few percent heavier per unit volume.
It will also be slightly darker if you look through a given thickness of it,
simply because there is now less water diluting the white/clear sugar and the minority brown stuff,
so the concentration of the brown stuff is a little higher.
Other things that happen with more heating is:
- the sugar molecules lose -O-H here and -H there, making water which boils away.
The remaining molecule becomes a bit more like plastic or char than like sugar.
- the sugar oxidizes from air contact, and browns,
and can even burn if you microwave it long and hard enough.
On the stove, these two things together are called carmelization, in their early stages.
In a microwave, it is possible to heat the middle of the batch without stirring,
so there may be less air contact.
So perhaps it is a little different than on the stove.
But mostly it is the same process.
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Update: June 2012