The Fresh Loaf

News & Information for Amateur Bakers and Artisan Bread Enthusiasts

Enzymes and microwaves?

  • Pin It
nicodvb's picture
nicodvb

Enzymes and microwaves?

Recently I'm exploring the microwave oven world, sometimes with surprisingly good results. I was wondering  how microwaves affect enzymes: do  theyget denatured or even destroyed? or are they only affected by the temperature increase implied by the microwaves? I mean, are microwaves "neutral" to the enzymes without considering the temperature increase?

davidg618's picture
davidg618

Bear with me, the answer gets a little "nerdy"

Some molecules--water is a good example--form a dipole. A dipole is a simple antenna, sensitive to particular radiation bands of radio frequencies. For example, TV "rabbit ear" antennae are dipoles, sensitive to the TV VHF band.  A microwave oven contain a radio frequency generator (a magnetron) that transmits energy from itself to foodstuff just like the TV broadcast station sends energy to the TV antenna. However, Microwave ovens are "tuned" to the radio band that can best transmit energy to foods that contain molecular dipoles, e.g., water, oil, etc.

Simplistically, if an enzyme contains even weak dipole structure, or are surrounded by water molecules it will absorb the oven's emitted radiation energy, i.e., heat up.

That said, I suspect food enzymes heated in a microwave, will denature at the same temperature as they would heated on a stove. For example, alpha-and beta amylase denature at about 168°F, and will do so regardless of where the heating energy comes from. Of course, in a Microwave oven, it will reach those temperatures faster because of the oven's efficiency. It's specifically, designed to heat food molecules quickly. Our gas and electric stoves, are  merely modern renditions of our ancestors' cave fires (and, admittedly, a bit more efficient, though not that of a microwave oven).

I think the complete answer requires examining every enzyme of concern at the molecular level. Some may be particulary sensitive to specific microwave radiation, i.e. "resonant", and denature instantly when exposed, while the surrounding food molecules are still warming.  Perhaps this research has been done by the food or oven industry scientists. A quick Google search didn't reveal any, but my search was far from exhaustive. The only reason I raise this caveat: I think we all have experienced bread, thawed or heated in a microwave oven, seems to have a "rubbery" mouthfeel. This has to be caused by the microwave energy permanently changing  something within the bread's molecular structure.

I wouldn't worry about it:-)

David G

 

 

 

flournwater's picture
flournwater

Excellent explanation David  ...  I'd have said "if it's alive and if it contains water, it's gonna die in the microwave".  Somebody should include your explanation in a chapter on bread making. 

Ford's picture
Ford

That was a good explanation.  I scald my milk in the microwave oven, but I would not bring my starter and or raw dough up to temperature for just the reasons you mentioned.

Ford

davidg618's picture
davidg618

Until I built my proofing box, I fermented my levain builds in the microwave oven with the door propped ajar to keep the light on for warmth. I was constantly reminding my wife not to use the microwave without removing the levain container, fearful it would get turned on with my levain still inside. Yeast dies at about 140*F; it would take less than a minute to kill everything in the levain's small volume.

David G