The Fresh Loaf

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Maillard reaction in a 212F/100C oven setting?

lanlanonearth's picture
lanlanonearth

Maillard reaction in a 212F/100C oven setting?

Hello,

I'm experimenting with low temperature (sprouted) bread baking, and I just baked a bread with oven temperature set at 212F/100C (boiling point of water).

The loaf was placed in a cast iron pot with lid. After many hours, the bread came out with a very browned crust. 

Is this the Maillard reaction? Maillard reaction should happen above 248F/120C so does this mean that the outer shell of the bread reached that temperature somehow even though the oven temperature was set way below it?

Does anyone know what exactly happened?

 

mariana's picture
mariana

Hi Ian, 

I know exactly what happened. Well, I think I do. 

What happened is that you placed your loaf in a cast iron pot with lid. After many hours in the oven it got much hotter than 100C. 

Here is why. 

You set your oven at 100C. The oven heats until the oven thermostat tells it that the AIR within is 100C. It then shuts off the gas (or electricity), and starts to cool. The air cools much more rapidly than the CAST IRON pot.

Assume that the oven thermostat has a "swing" of 10C. When the air in the oven drops to 90C, on comes the gas to heat the oven once again. At that moment, the cast iron pot would be significantly hotter than the air. The gas (or electricity) keeps cycling on and off in this fashion for many hours, each time increasing the temperature of the cast iron pot. 

In essence, you had an oven inside an oven. The big oven had been set at 100C, but the cast iron mini-oven with bread inside it got much hotter with time, never cooling enough along with the air around it, but always being heated more and more and more, possibly reaching 200C. That is why you got a very brown crust inside it. 

GaryBishop's picture
GaryBishop

I guess the oven would have to be dominated by radiant heat for this to happen. 

An easy experiment would be to put an oven thermometer inside the pot and leave it in the oven for a while before checking. 

mariana's picture
mariana

Hi Gary

it is not a theory but a method home bakers use to recreate a professional oven at home. If we place bricks inside our oven and heat it long enough (1.5hrs) setting it at 500F, eventually our bricks will reach 700F and we may bake bread and pizzas in the same way as bakers do in old brick ovens. 

Like that

 

or like that

 

Described here, please scroll down to the section: Simulation of a More "Complete" Masonry Oven by Kenneth Sole

http://www.theartisan.net/oven_humidity.htm

An easy experiment would be to check the temperature of a cast iron surface (or bricks) with laser thermometer from time to time. Such thermometers are very affordable and more accurate than oven thermometers. 

GaryBishop's picture
GaryBishop

I'll try tomorrow with a cast iron pan in a 200 degree oven. 

The part I don't understand is the physics. If heat transfer was happening via the air (convection), I think reciprocity would require that the pot would heat the air as much as the air heats to pot and they would be the same temperature. 

But with the heating element directly in the stove (gas or electric) there must be significant radiant heating. I guess the heat transfer away from the pot by convection is less efficient than transfer to it by radiation so its temperature rises. 

mariana's picture
mariana

Gary,

I think it has to do with how oven knows that the air is hot enough. My oven has a small nail-like thermoprobe in the top right corner of the oven. It sticks out and it's the temperature of that thermoprobe that is detected, of this metallic 'nail', thin and not longer than a couple of inches . Across it, in the left top corner of the oven is the opening, where heat vents from the oven. It is not a completely enclosed system, where air circulates and heat cannot escape, and is always transferred back and forth between air and the pan. 

My oven assumes that this little nail's temperature is equal to the temperature of the air in the entire oven (mine is 6.3 cubic feet). This little 'nail' in the distant periphery of the oven cools down quicker than a massive iron pot, when the heating element is off and the heat continues to escape through the vent, and that is why cast iron accumulates heat over time. 

GaryBishop's picture
GaryBishop

brick lined oven

I wonder if the reason the above configuration gets above the set point is the bricks are holding down the temperature around the probe so the oven continues to heat resulting in the middle area getting hotter?

I also keep thinking about radiant transfer. Much like a child's slide getting hot out in the sun. The slide surface can get much hotter than the air temperature because radiant heating from the sunlight is adding energy faster than convective cooling to the air can remove it. 

If the heating elements stay on and glow red, I would expect a similar effect. 

GaryBishop's picture
GaryBishop

I put a cast iron pan into my oven and set the temperature for 210 degrees F. After one hour the highest temperature I could find inside the pan was 205F. After two hours the highest temperature was still around 205F. I see no evidence that the temperature of the pan is exceeding the oven set point. 

From past experience with my oven I know that the set point is the temperature that the heating elements turn off and the swing is about 20F. When set for 110F (fermenting yogurt) and measuring with my bluetooth thermometer in the oven I can see the temperature swing from 90F to 110F with the average about 100F. My bluetooth thermometer is only rated to 140F so I couldn't use it for this experiment. 

Here is a photo of my experimental setup.

I measured the temperatures with a Kintrex IRT0421 optical thermometer that I have previously compared for accuracy with my Thermapen 5. 

mariana's picture
mariana

Thank you, Gary! Do you bake your round loaves in this cast iron skillet? Is it deep enough for taller-semicircular round loaves? How much does it weigh? 

I will test the same in my oven with a larger cast iron pot, usually used for bread baking. I assume it will retain more heat, but who knows. One is 10 lbs of cast iron, looks like this Lodge, but 2x bigger and deeper, antique

 

another is 16lbs of metal for larger loaves from 1kg of flour. I will place an oven thermometer inside the pot, since it's an empty run anyways. And check its surface temp with a laser thermometer. 

I will post my results here. My oven doesn't have radiant heat, the heating element is hidden underneath the oven flour, so I sometimes bake things straight on the oven flour. 

For the topic starter, if you are reading this: it is also useful to check the accuracy of your oven Temp setting. Sometimes it is up to 20-30 degrees off, not exactly what you ask it to do. Maybe that is the cause of crust browning. This particular bread is full of natural sugars, due to sprouting and the lowest temp of sugar caramelization which makes crust brown is 110C/230 for fructose. If the pan or the oven air reaches this temp, it iwll brown the crust, for sure. 

GaryBishop's picture
GaryBishop

It was just one we have that I thought would serve for an experiment. I bake in Pullman pans from 4x4x4 to 13x4x4. 

I'm very interested to learn your results. I'm not planning to do bake this way but I enjoy learning how things work. 

I've also experimented with low temperature baking in the past after learning that real pumpernickel bread was baked long and slow using the last heat in the ovens. 

Interesting that your stove has the elements hidden. I think I'd really like that. 

Checking their oven temperature is a good suggestion. They can be far off especially at the low end. 

mariana's picture
mariana

Hi Gary, 

I heated a 16 lbs cast iron pot, closed, with oven thermometer inside the pot, for 2 hrs, oven set at 220F.

After a few minutes the oven air reached 220F and shut off the heating elements. At that point top and bottom of the cast iron pot were also 220F, but the sides were cool, at 145F. Oven thermometer inside the pot, measuring the temperature of the air inside the pot, indicated about 210F.  So far so good. No crust browning, for sure. Not right away. 

After 2 hrs sitting at such temp in the oven, it was at 230F top and bottom surfaces of the pot, 220F sides of the pot and ... tadam... 340F inside the pot, given by the thermometer sitting inside the pot, under the cover.

It accumulates heat inside! And that heat has nowhere to escape! Basically it is the same result as with the stones or bricks in the oven. The surface may be the same temp as oven air, but inside they are hotter and they don't cool down as quickly as the air in the oven. 

I guess that is the cause of the browning of the crust inside the pot. Not all heat was transferred from the bread crust to the bread crumb during cooking and it got browned. The bread crumb cannot be hotter than 98-100C, so the excess of heat inside the pot is all staying as hot air underneath the pot cover and as hot bread crust during baking time. 

See if you place your oven thermometer inside your cast iron skillet covered with its cover and if it gives you the same results over time. 

GaryBishop's picture
GaryBishop

OK. I'll try to reproduce that experiment tomorrow at lower temperatures. Our oven thermometer died but I can use my bluetooth thermometer below 140F. I'll set the oven for 110F and see if I can get higher temperatures inside the pan. 

Was your pot directly on the bottom of your oven? Or on a rack? 

mariana's picture
mariana

Gary, it sits like so (still heating, I will give it full 4 hrs, to see what gives). In the middle, on the rack. 

oven thermometer inside the pot

The air inside is hotter than outside

GaryBishop's picture
GaryBishop

I put the pan in my oven set to 110F for 5 hours and the highest temperature my bluetooth thermometer measured was 106F.

mariana's picture
mariana

Gary, thank you. It never even got up to 110F. 5% difference. I don't know if it's significant or not. For biological systems, like sourdough fermentation, yeast gassing power, and the speed of doubling of the microorganisms in the starter, it is. After all 41C fever is bad, but it probably won't kill you, while 43.5C fever will cause brain damage. But for baking 5% difference in temperature is not important.

Did you measure the temperature of the metal, of the cast iron pot top/bottom/sides? Did it reach 110F ever? Did you oven reach 110F at certain point? I guess it's difficult to know without a separate oven thermometer hanging on the rack somewhere. 

Mine was set to 220F and the walls of the pot reached 220F and stayed at it for full 5 hrs, the lid and the bottom of the pot reached 235F, the air inside fluctuated between 320F and 340F. I don't know if it's because I was opening the lid to peak inside, or because the lid is not fully sealed and the temp of the air inside was escaping/inflowing a bit and exchanging heat with the air inside the oven. 

I ordered a different oven thermometer from Amazon today. I will repeat the experiment tomorrow to exclude the possibility that there is something wrong with my old Kitchen Aid thermometer. I am very sure in my laser thermometer, I double checked its accuracy with a Thermapen. 

GaryBishop's picture
GaryBishop

I'd like to get a new one. May I ask what you bought?

mariana's picture
mariana

Gary, I got 2 commercial oven thermometers, they are NSF approved and cover the entire useful range of 60-580F. Seem to be highly affordable and highly rated. I will use one to monitor the air temp inside the pot and another - outside the pot. 

Rubbermaid Commercial FGTHO550 Stainless Steel Oven Monitoring Thermometer

https://www.amazon.ca

https://www.amazon.com

NotBadBread's picture
NotBadBread

Thank you for this educational thread! How can we get a physicist to weigh in?! I am certainly not one, but I think the concept of heat capacity (or "thermal mass") might help explain why you guys are having different experimental outcomes. To sum up, it seems like it depends quite a bit on the characteristics of the vessel you're using in the experiment: 16lb of steel vs 10lb vs 5lb would all behave differently in this experiment, I'd wager. As mariana mentioned, the trick of putting in *extra* mass -- via bricks or stones -- would also have an effect.

So, depending on what pots/stones you're using, you may both conduct similar experiments and come away with quite different data!

GaryBishop's picture
GaryBishop

My son-in-law is a PhD physicist. I checked with him. 

On his advice I have ordered a dual thermocouple thermometer to try the experiment measuring the air temperature both inside and outside the pan.

He thinks the described behavior may defy the 2nd law of thermodynamics

It is impossible to construct a device that produces no other effect than transfer of heat from lower temperature body to higher temperature body

I think the dynamic nature of the situation with lots of different temperatures, spatial separation, air leakage, radiation, etc. makes it very hard to reason about what is happening. 

I'll repeat the experiment with the dual-probe thermometer when it arrives. 

mariana's picture
mariana

The heating elements in the oven will get very hot or red hot, even though they heat air and cast iron only to 100F or 200F, or 400F for baking, let alone the temperature of the gas flames in gas oven. Their temperature is 1000C, 1800F.  So, no problems with the second law. 

I think the best would be for the topic starter to actually measure the temperature of their oven carefully with an independent oven thermometer and the temperature of their sprouted grains bread crust to see if it gets hotter than 100C.

Our experiments with our kitchenware and our ovens do not recreate the situation in their kitchen.

Anyways, if one is sure that their oven is set to 100C and keeps 100C, then it would be enough to cover the cast iron pot not with its own lid, but with aluminum foil with a small vent or two in it, small holes, for air circulation. This way, the bread crust won't brown, provided it is situated far enough from the gas flames with their 1000C.  

lanlanonearth's picture
lanlanonearth

Wow I left my comment (as a newbee) not sure if I will get any response (as I saw previous topics in this thread were from weeks away), and now I come back seeing all these information! I just love you all...

I haven't read through all of them yet, and firstly thank you Mariana and Gary for the explanations and experimentations! I did have a regular thermometer to check the oven temperature so it's not oven fluctuation (the 212F/100C read is from the thermometer inside, not oven knob. However, I have a much smaller oven, and my cast iron pot is sitting directly above the bottom heating element (top heating element is quite close also). So, now, with your explanations, I think it may have a lot to do with that. The pot is more like sitting on a stove instead of only being enclosed with hot air. And as the loaf bakes and dries, its temperature probably got out of control.

I will do an experiment with an empty pot too. Thank you Mariana for suggesting to put a thermometer inside the pot which I just never thought of. I will upload pictures once I make the experiment so you can see what my situation is like. This is so interesting I've read about true pizza needing much higher temperature than home oven and never thought that an work-around existed!

Thank you to everyone else too on sharing your thoughts. I haven't read through everything yet. Will take some time to do so now :-)

 

GaryBishop's picture
GaryBishop

I finally got around to more carefully repeating the pan temperature experiment. 

I used a dual probe digital thermometer in my iron pan starting with a cold oven set to 200F. In my oven the set point appears to be where it turns off the heating elements. 

The maximum temperature inside the pan over a 3 hour interval was 189.7 with an average of 186.4 over the final hour. 

The temperature outside the pan max was 221.2 and the average over the last hour was 195.4.

The traditional oven thermometer placed inside the pan read 190 when I open the pan at the end of the experiment. 

The bottom line is I can't see any heat buildup in the pan in my oven. Rather it stays near the average temperature of the oven as I would expect.