Proofing Box

Franko and Andy,

I considered controlling humidity but didn't for a bunch of reasons.

I don't know what an "ideal" relative humidity is for proofing breads, and whether it is the same for all breads. I didn't have any idea how to do it in a practical (and inexpensive) way. I was concerned about water vapor condensing on the electrical components. I searched TFL for discussion threads. None were relevant, and most were complaints about highly humid weather. One post, in June 2008, specifically asked if anyone might suggest what the ideal temperature(s) and humidity(ies) is/are. There has not been a single response in 2 and 1/2 years. Searching Google revealed (as I suspected) maintaining a constant temperature and relative humidity is a complicated (and expensive) engineering challenge.

So the box is as tight as reassonably possible. I took precautions cutting and fitting the wood joints, all are glued with waterproof glue, the two penetrating holes (for electrical power) are stuffed with cotton wool, and I was especially careful fitting the doors.

Furthermore, with some exceptions, e.g. ciabatta, foccacia, challa, sweet rolls and ryes, I proof the majority of my breads in baskets, between couche folds, or panned. Ciabatta is dusted with flour, focaccia coated with olive oil, challah and sweet rolls glazed with egg wash, and rye breads cornstarch glaze. All the rest, the majority, I cover with dampened towels. I've done this for decades--long before I caught the obsessive bread-baking virus.

The point is, I think the proof box, as built, creates a stable environment, i.e., tight temperature control and an unknown but reasonably constant relative humidity.

A relevant digression: Before I retired I was a system engineer, and, often, a program manager for developing prototypes. I constantly enjoined my engineers not to "over-engineer". Engineers love to create, just because they can. I frequently laughed at myself during this project breaking my own dictum. I think I built it, yes, to "control" my bread-baking more closely, but I confess I had as much fun making the box as baking a loaf.

David G

I recently used the box at 89°F. It worked fine, but only--just like baking--after pre-warming the box. It took about twenty minutes from 70°F In the dough making I set the Desired Dough Temperature at 89°F also. The light doesn't generate a lot of heat energy. It does a fine job maintaining a desired temperature, but won't heat up a large volume of chilled dough rapidly.

David G

I've been ranting lately about Desired Dough Temperature in another thread. It's premise is select it intentionally, and hit it as close as possible, especially if you are using a homemade proof box and temperatures significantly above room temperature.

http://www.thefreshloaf.com/node/21632/desired-dough-temperature-ddt-further-considerations

I've also made the comment here argueing, without specifics, that heat transfer into dough, using air born temperature difference only is very slow, and, because of that, one should raise the DDT to the intended fermenting temperature. A proofing box will be very good at maintaining dough temperture, but a very poor performer changing it.

Yesterday, I took a stab at making Tartine country bread. Robertson makes a big deal out of fermenting at 80°F. My room temperature yesterday ranged from 67°F to 72°F during the 3 and 1/2 hours fermenting the dough, and the subsequent 2 hours proofing the loaves (78°F prescribed). Obviously, I needed some form of proofing "microclimate" (Robertson's word, not mine.).

I've tried using my oven, but have found managing the temperature annoying. Leaving the lights on the air temperature climbs to 110°F within 20 minutes, and boiling water cools to about 8O°F in the same time, through evaporation. The microwave, with the door ajar to keep the light, gives me a constant temperture (~77°F), and the interior is too small to hold anything other than two small bannetons, thus preventlng using hot water (and forget about proofing baguettes longer than 10"). These are the primary reasons I built the proofing box.

I missed the DDT by minus two degrees, and after I'd mixed the dough in a stainless steel bowl, at room temperature, I was down to 76°F before I put it in the proofing box, bowl and all, covered with a towel I'd dampened with hot tap water. The dough weighed approximately 1.8 kg. The proofing box was set at 80°F. The dough's middle temperature after a 45 minute autolyse, and the first turn--a few minutes in the bowl at room temperature--was 76.4°F. I increased the thermostat setting to 82°F (more about this in a moment) After the second, third, and fourth turns--still in the same stainless steel bowl. the dough's temperature was 76.8, 76.8 and 75. 4 !!!. What?

I finally realized that the even though it took only a few minutes to turn the dough, with its low specific heat, the stainless steel bowl was dumping heat rapidly to the cool room. I'd taken a few minutes longer manipulating the dough for the fourth turn feeling that the dough's gluten wasn't developing quite as I'd like.

I quickly transferred the dough to the plastic container I normally ferment dough in usually beginning after the first S&F. My routine doughs are at 68-70% hydration and I find leaving them in the bowl and doing a bowl turn before beginning bench S&F's is less messy. Robertson prescribes bowl turns throughout the fermentation process so I'd figured "Why dirty another container?".

At the end of the 5th turn the doughs temperature was 77.8°F. I still wasn't happy with the gluten development, so I did one bench S&F, felt the resistance I'd wanted, and returned to dough to the proof box. I didn't bother taking the dough's temperature. I shaped the loaves, put them, covered (dry towel) into the proof box still set at 82°F. I chose not to take their temperature preferring not to poke holes, even in the bottom of the loaves

One last comment: I've said before heat transfer into bread dough is a complicated process involving the dough's initial temperature, surface area to volume ratio, and its a physical property known as specific heat. In a proofing box relying entirely on warmed air to carry the heat energy, the air's temperature vs. the dough's temperature is, of course, also a factor. The optimum range for yeast (commercial) development is 68°F to 81°F, with maximum production at 79°F (link 1). Similar curves(Link 2) show similar performance for yeast associated San Francisco sourdoughs.

Link1: http://home.earthlink.net/~ggda/yeast_treatise_frameset.htm

Link2: http://aem.asm.org/cgi/reprint/64/7/2616

I use 90°F as a safe upper limit to ferment dough, and therefore the highest setting I'll heat the air in my proofing box to. Even though the center of a dough mass will remain cooler, the air's temperature will ultimately penetrate an undisturbed dough deeper and deeper toward its center, with yeast growth diminishing in more and more of the fermenting dough. Periodic manipulation, e.g. turns and S&F evens out the dough's temperature distribution, so all temperatures above 82°F will ultimately slow down yeast growth. The consequence is there is only a small differential between usual room temperature and 82°F in which to operate.

Obviously, the way to warm dough quickly, i.e., transfer heat energy into the dough most rapidly, is use a large heat source, at a non-damaging temperature, and manipulate the dough rapidly and continuously. But, of course, we already do that; we call it mixing which puts us right back to the importance of DDT.

David G