Measuring bread machine baking pan temperature
Spring is here... soon it will be too warm to use the large indoor oven. It's the season for min-ovens (MO) and bread machines (BM) to be used more frequently, often set up out on the porch.
Over the last year or so I've tested dozens of BM's, looking for the ones that do the best job at mixing/kneading, fermenting/proofing, and baking. This thread is about the baking part.
My tests revealed that most BM's are pretty ho-hum bakers, with maximum baking temps in the 255-300ºF range. This is OK for soft crusts and spongy crumbs, i.e. sandwich bread. But most bread recipes call for much higher temps than that.
Communicating with several manufacturers (most notably Zojirushi, Panasonic, and Saki), I learned that the temps that matter are not the air temps inside the oven chamber; it's the baking pan temperature. That's what they design for.
So how best to measure that? It's easy to imagine an elaborate, automated setup with contact probes and computerized logging to do it. But we don't have to go there. I am getting excellent results (i.e. results that match the manufacturer specs) using an infrared thermometer. More on that as we go.
So, what exactly are we seeing when we measure the baking pan temp? We're seeing how the BM's computer senses the temp and controls the heater elements to get the temps they want. The primary technique used for controlling the temperature is changing the on/off cycle times (aka "duty cycle") of the heater element. More time on than off = hotter.
To start things off, we'll look at one of the popular Zojirushi dual paddle breadmakers. Well-built and very versatile, they are probably the most highly-regarded "high-end" BM out there. I've tested all models prior to the "Virtuoso" (which has a 2nd heater in the lid), and they're pretty much identical baking-wise. Let's see how they do as bakers. The unit I'll test is the BB-CEC20, aka "Home Bakery Supreme", a classic that is still being made and sold today.
Zoji is one of the few companies who give pretty accurate time and temp data for their machines' cycles. For the bake cycle, the temp range is 254º (for Light crust) to 290º (for Dark crust). Since we're looking for its maximum baking temp, I'll use Dark mode, and 290ºF is the number to look for.
I've done this test with the stock pan several times in the past. But one of the cool things about the Zo is how easily it accommodates other pans, and Zo users frequently use them in their bakes. So I'll try that this time. The stock pan is aluminum so I chose a standard 9"x5" pan, also made of aluminum. Its weight is about half of the standard pan, so it should warm up more quickly. To simulate the size and mass of the dough in the pan, I used a mix of vermiculite and rice.
Here is the oven chamber of the CEC20. I made a trivet to raise the pan bottom to the same height as the standard pan. Note that the heater element enters on the right and wraps around the bottom perimeter. Also note the location of the temperature sensor on the back wall.
Here's a pic of the setup, showing where to place the infrared temp gun when measuring. Place it at the opposite end of where the heater elements enter the chamber. It needs to point at, and be perpendicular to, an exposed part of the pan. So don't do this with a full-size loaf; leave an inch or so at the top to measure. Oh, and DON'T do it with the lid wide open!! To minimize heat loss, only open it enough to get the gun in and take a measurement. Quick in and out... takes 4-5 seconds max.
Experience shows that 45 minutes is a long enough bake to see the computer's temperature control action. So this is a 45-minute dark mode bake. The list shows the pan temperature at the time remaining, in 5-minute intervals.
:45 Dark bake
:40 145º
:35 199º
:30 216º
:25 248º
:20 262º
:15 275º
:10 291º
:05 298º
:01 293º
The Zo is a very conservative baker and heats up slowly, even with the lighter-weight pan. It took 35 minutes for it to reach it's 290º maximum temp and settle in there. The heater element cycles on and off from the very start, and is never on for longer than about 30 seconds at a time. After about 15 minutes, it settles into "8 seconds on, 22 seconds off", or a 36% duty cycle. Even with a 700-watt element, this is very conservative heater action.
This measurement technique is easy to do and plenty accurate enough to assess the baking behavior of bread makers. In coming installments we'll see how some other machines bake, and maybe find ways to "trick" the computer into letting them bake hotter.
Comments
My old IR thermometer is very temperature sensitive (I mean to the ambient temperature, presumably because the solid-state circuitry itself is temperature sensitive). I imagine that's still true of most of them today. So be careful not to let the body of the instrument heat up, which is most likely if one tries to make several repeated measurements.
TomP
At those "low" temps, it is amazing to be able to bake many different breads and get them to 207F in 50 min.
Thanks for the temp chart/table!
It will be handy for getting a nice cozy rising box in winter.
Really? That's hard to believe in a Zo.
It IS a great rising/proofing box, though. And a good mixer/kneader.
Hi Precaud,
Does it contradict a principle of heat?
The loaf for daily meals is 100% wh grain, total 945gr, and I take it out after 10 min Preheat and 50-55min bake. Preheats hardly do anything to raise the temp of the loaf-it does give it a little more rise.
Even heavy 90% ryes bake to over 200 though I do keep the loaves smaller.
Do you seal your upper window off?
I try for 205-206 but usually it is 207-210F.
The cavity temp is often 400F but as you say there are cycles of fluctuation.
I am using my panasonic for mixing nowadays (almost exculsively ) :)
Hi Jo,
I never got internal temps like that with any Zo I've had. Or any other BM ! ***
I'd like to try to duplicate your results. Is this with a standard program, or a custom cycle? I assume you're using Dark crust.
And what is a 10-min preheat? Bake running for 10 min before putting the pan in?
You get these same internal loaf temps with both of your Zo's? (I know you have 2 different models.)
So far I only put foil on the outside of the glass, not inside yet, I'll do that if I decide to keep it.
*** Here at 7,000 feet, water boils at 199º, so I never see internal temps as high as you do at sea level.
At 6000 ft, water boils at 201 deg. F, and I used to bake my loaves to 197 - 199, those times that I measured them. Those temperatures near the boiling point only mean that much of the free water has been baked out. The actual temperature isn't very significant otherwise.
TomP
is consistent with what I see as well. But what does "baked out" mean? It doesn't disappear.
I'm not conviced that the lower boiling point has no other significance. Water is a great conductor. If it changes state at a lower temp, that would definitely influence transmission into the loaf.
If the interior were to rise above the boiling point, that would only happen if virtually all the water were gone. Otherwise the water would boil and keep the temperature at the boiling point. If there is still water in the loaf and it's being heated, the water near the surface will evaporate and cool the loaf. The more water that is evaporating, the lower the loaf temperature.
By "no significance" I meant that whether the internal temperature is (at sea level) 195 or 200 or 205 or 210, the interior is adequately cooked and will not seem raw or undercooked or gel-like. At higher altitudes the interior may not get above say 197 but it will still be cooked. I think that similar loafs at different altitudes will be cooked similarly at say 5 deg F below the boiling point, whatever that is point is.
But go high enough, where the boiling point is drastically lower, and the situation could change. Near the top of Mt Everest the boiling temperature has been estimated to be 154 deg. F. I don't think your bread is going to seem cooked at that temperature - the interior will still be a gel.
My first model is X20.
I have the final proof done with finger test .
Then I put a light score and in my own pullman pan.
My trivet is 48mm high.
I custom program the Zoji to have a 10 min Preheat and then 70 min bake.
PS My crust is Medium. I put a milk powder/milk wash to get a better color.
(I test dough temp at 53-55 min into the bake. Total time in the BM is 10+55 min).
I put the dough (clas dough which has been fermenting at 33C) in its pan in Zoji.
It sits while the Zoji is preheating.
I have to take my 2nd Zoji to my parents' house so I can bake there. Actually I need to open and use it!
for the details. Your X20 is nearly identical to the CEC20 I tested. They even look the same.
FYI, Preheat on Zo only warms the chamber to ~75ºF. It is to warm up ingredients before mixing, it is not an oven preheat.
Interesting you are doing Medium crust, that would be even lower temp, like 280º.
I wonder, have you checked the calibration on your probe thermometer? Check to ice water (32º) and boiling (212º where you live).
Ok
I boiled some 2 inches of water in microwave- it was 209.5F.
The ice with tap water was put into the freezer- 10 min. It was iced over but the water was is 31.8F
So, yes the temps are a little off, but the therm even registers a loaf at 209+F when I overbake.
Thanks for checking, and sorry for giving you extra work :( Just trying to understand the discrepancy.
If those figures are correct, then we have to say that baking at sea level, heat transfer into the loaf is more efficient than at altitude.
tpassin basically suggested the same thing in his post, but hedged it a bit:
Similarly, yes, but not identical. Especially in a pan bake, where all the moisture can only escape through the top crust.
It's an interesting sidebar to the thread's topic.
Yes, most of my experience in the area of elevation is with baking free-standing loaves. I used to go back and forth between New Mexico (6000 ft elevation) and Virginia (700 ft elevation) twice a year. Spring and fall in NM, winter and summer in VA. In NM I had a gas stove, in VA I had an electric one. So far as I could tell, the same kind of free-standing sourdough loaves baked up the same in both places at the same nominal baking temperatures. Possibly I used slighty higher temperatures in NM, I don't remember exactly any more, but if there were differences they were small. The baking times were the same - within a minute or two which you can hardly notice in the end result anyway. Of course the interior temperatures had the differences we talked about earlier. One other difference would have been the humidity in the air. It NM it is very low, in my air-conditioned house in VA it's higher.