Chilling the Bowl Before Creaming Butter and Sugar

A couple of days ago I wrote on the difference between creaming butter and sugar together in a small bowl versus a large one. I wanted to look at the difference chilling the bowl before creaming makes, so I put the small bowl in the refrigerator overnight before I creamed the sugar and butter. Before I report those results, this is what I obtained before, with everything at room temperature (meaning literally room temperature - the butter, bowl, and beaters had all been sitting out overnight):

0 - 314 - 260
1 - 274 - 220 - 18.2%
2 - 253 - 199 - 30.7%
3 - 239 - 185 - 40.5%
4 - 231 - 177 - 46.9%
5 - 225 - 171 - 52.1%
6 - 224 - 170 - 52.9%
7 - 220 - 166 - 56.6%
8 - 217 - 163 - 59.5%
9 - 215 - 161 - 61.5%
10 - 212 - 158 - 64.6%
11 - 216 - 162 - 60.5%
12 - 213 - 159 - 63.5%

For a description of the rationale behind the procedure, see my post from Jan 29, 2010.

The numbers in the left column are the number of minutes from start of creaming, the numbers in the second column are the weight in grams including the cup, the numbers in the third column are the weight of the level cup of creamed ingredients not including the cup, and the right column is the percentage increase in volume from the starting volume of butter and sugar.

For the chilling experiment, as I said, I placed the small bowl in the refrigerator overnight. I can't measure the temperature of the bowl directly, but my inaccurate thermometer says an item in the refrigerator is at forty degrees. I say inaccurate, because it says freezing water is 32, but it says my sixty-eight degree room is actually at sixty degrees. By interpolation, the reading of 40 would mean 41.7 degrees. On the other hand, the nearly unreadable gradations on the dial make my reading of 40 subject to at least that much error. I should just say the bowl was "in the vicinity of 41 degrees," I guess. It sure bugs my scientific nature! Argh.

Anyway, for this experiment I tried to minimize the time I spent doing the initial mixing of butter and sugar, but it didn't mix as easily because the butter cooled from room temperature as it gave up some of its heat to the bowl. By the time I finished mixing the butter and sugar by hand, the ingredients in the bowl showed a temperature of 70.1 F. My "room temperature" fluctuates a little day to day, but that seems to indicate the ingredients were still at approximately room temperature when I started creaming. The creaming results were:

0 - 311 - 257
1 - 244 - 190 - 35.2%
2 - 212 - 158 - 62.7%
3 - 201 - 147 - 74.8%
4 - 209 - 155 - 65.8%
5 - 210 - 156 - 64.8%
6 - 209 - 155 - 65.8%

That pretty interesting!

For convenience, here are the numbers side-by-side for direct comparison. Left column is minutes, center column percent increase with room temperature bowl, right column increase with chilled bowl:

0 - NA - NA
1 - 18.2 - 35.2
2 - 30.7 - 62.7
3 - 40.5 - 74.8
4 - 46.9 - 65.8
5 - 52.1 - 64.8
6 - 52.9 - 65.8
...
10- 64.6 - NA

With the small bowl at room temperature, it took ten minutes to reach the maximum volume. With a chilled bowl, it only took two minutes to reach approximately that volume! And the maximum volume in a chilled bowl was at three minutes, with a 74.8% increase instead of only a 64.6% increase.

I measured the temperature of the butter when I was done - 72.1 F. So the temperature increased from 70.1 to 72.1, a 2.0 degree increase.

In my original experiment with everything starting at room temperature, the temperature started at 69.3 F. and increased to 76.7 F., an increase of 7.4 degrees to a significantly higher temperature.

I don't think those start and end temperature measurements tell the whole story. First of all, the temperature I measured at the start of the chilled bowl experiment is definitely what the thermometer measured, but it doesn't reflect what I saw happen during the experiment. The first few times I took the ingredients from the bowl to measure their weight, the butter was definitely a little stiffer than I'd seen in past experiments with everything starting at room temperature. I had noticed that by the time I had finished mixing the butter and sugar by hand in order to get the initial "time 0" reading, the bowl had lost some of its chill, but it was still well below room temperature. I think that the beating process in the mixer increased the rate of heat transfer to the bowl, so for the first couple of minutes at least the butter continued to be cooled by the bowl. The measurements at 4, 5 and 6 minutes in the chilled bowl had passed the point of maximum volume. I am thinking that cooler butter holds a greater amount of air whipped into it, and that as the creaming continued past three minutes the bowl had fully warmed to room temperature, and the butter and sugar had finally reached "room temperature" and lost the ability to hold that extra air which cooler butter has; then the volume decreased to what room temperature butter can hold.

It would be interesting to measure the temperature of the butter after two minutes of mixing - I would expect to see a somewhat cooler temperature, but maybe no. It would also be very interesting to see this in the large bowl. The size of the bowl is larger, and would draw heat from the ingredients more rapidly; but the amount of ingredients would be doubled. Which would win out in the temperature battle? I may try it. However, I mentioned before that these experiments are flawed, because they involve pauses to measure volume in the middle of the creaming process. That pause is especially harmful when there are potentially significant temperature changes occurring during the process, as in this experiment. So if I do this again, I think it needs to be a much more time-consuming and more costly experiment with chilling the bowl again and starting from scratch for each measurement; and then doing each one three times to get average values. I really should do it, but I'm short on bucks so I have to plan that. I don't have to do it all at once; maybe I can just do one time point a week or something until I have the full data.

It's worth mentioning that sometimes people recommend chilling the beaters in addition to the bowl. My beaters definitely get warm, quite warm, while beating for a length of time. The beaters are a conduit for heat directly from the motor into the ingredients. That's not so great. I wonder if new mixers, or better mixers, do a better job of insulating the ingredients from the motor heat than my 40-year-old Sunbeam Mixmaster does? At some point maybe I'll check to see how much difference it makes to chill the beaters before mixing. Off hand I'd guess it doesn't really make that much difference when the beaters are a direct conduit from the motor, because metal is such a good heat conductor and so they warm up very quickly from the motor. Plus their volume is quite small compared to the bowl, and so the effect of cool metal beaters would be much less than the effect of a cool bowl. But only the numbers tell the true story.

My mixer has glass bowls. The glass is pretty thick. My impression is that they probably remove more heat from the butter than modern stainless steel bowls would, but I'm not at all sure of that. It would be interesting to know. If you, reader, have stainless steel bowls, you would probably want to know the results on your own mixer before drawing any hard conclusions from numbers from this experiment.

I have an initial impression from this, though. Chilling the bowl is a great idea if you want to get maximum volume quickly, or if for some reason having the butter warm above room temperature causes a problem with the recipe. Or if it's a hot day and your butter is simply too warm. The chilled bowl does keep the temperature down significantly, and if the butter was warm it would cool down rapidly. However, I have read that if you cream for too long, the butter gets too much air in it and the cookies go flat. With the chilled bowl, the butter gets to the maximum amount of air quickly. It seems like that would make it easier to go past the point where you're creaming too long. In addition, the rate at which air is incorporated is dramatically increased. From the standpoint of reproducibility, if you want to aim to always get the same amount of air whipped into your butter, you have to be a lot more accurate in your timing and procedure if you start with the chilled bowl, because the rate at which air gets added is so much higher.

To clarify my last point - the small chilled bowl seems to have a rate of volume increase of about 31% per minute for the first couple of minutes. The small bowl at room temperature has a rate of volume increase of about 16% for the first couple of minutes. Suppose you were aiming for a volume increase of 30%, plus or minus 2%, in your dough. In the chilled bowl, you would cream from .9 minutes to 1.03 minutes, or from 54 to 62 seconds, to get your dough to where you wanted it. In the room temperature bowl, you would cream from 1.75 minutes to 2.0 minutes, or 1' 45" to 2 minutes, to get it to where you wanted it. With the chilled bowl, you have a leeway of 8 seconds; with the room temperature bowl, your leeway is 15 seconds. As humans, it's hard for us to do something that takes a while and be sure to end within an eight second window, but a fifteen second window is definitely easier. I guess I should speak for myself! But I would be lot more comfortable with the idea of following a procedure correctly if it has a 15-second leeway than an 8-second leeway for error.

Whether those numbers are relevant to anything is unknown right now. The next sort of question to ask along these lines is, how much volume increase do we want to aim for in cookies, and how much difference does it make if we get more or less than that? And then finally, what exactly should we do to get that amount of volume increase? For us home bakers, I don't know if we can aim for precision like a professional baker might -I think it's kind of difficult to aim for always having everything at exactly the right temperature and do things for exactly the same amount of time. But some people actually are pretty good at that, and mostly it just takes extra effort to get there. My goal is to find out what makes a difference, how much difference it makes, and what happens if things are varied by so much, and then I and others can decide how exacting they want to be in their efforts.