Mysteries of genoise finally cracked!
Posted: 26 May 2011 01:33 AM   [ Ignore ]
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After cranking out sad, flat genoise, one after another, I am extremely elated to announce today that I finally made a successful genoise—1.5 in. high at the center, 1.25 in. high at the edges, and almost no flour nuts! What’s more, I was able to do all of this without a scale, so yes, it is possible, just cumbersome and perhaps not so consistent.

Since I finally figured out what went wrong with all those failed genoise, I want to share what I learned from the experience. Essentially, most of the factors that can screw over your genoise happens before the cake gets in the oven. The only thing that can really go wrong once the batter is in the oven (assuming it was properly mixed) is wrong oven temperature or opening the oven door before the cake is done. If you are having trouble with the genoise classique, go through this checklist as you are making the cake.

MEASUREMENTS:

The most crucial measurements are for the eggs, since they provide the structure. Weigh yolks and whites separately. The recipe calls for 4 large eggs (200 grams), so you need 120 g whites, 80 g yolks. (30 g/white, 20 g/yolk, 50 g/large egg) If you do not weigh yolks and white separately, you may not be getting enough yolks, which stabilize the egg foam. If you are using volume measurements, you need 3/4 c.+1/2 tsp. eggs (total volume) of which 1/4 c.+2 tsp. must be yolks.

EGG TEMPERATURE:

Temperature is the important. If your eggs aren’t at the right temperature, you won’t have the right volume or stability. MEASURE the temperature of your eggs! Calibrate your thermometers in boiling water if they are not accurate. I have a thermometer that doesn’t go up to the boiling point of water, so I had to calibrate it with another thermometer, taking four data points (reading vs. actual temp.) and doing a linear regression on Excel.

In Shirley Corriher’s Bakewise, the recommendation is to heat the eggs no more than 90 deg F, so that the majority of the beating time will fall in the range of 75-80 deg, which is the optimal beating temperature for the eggs. Rose says to heat the eggs just to lukewarm or room temperature. Talking with some folks on this forum, Julie recommended 110-115 deg; Loopy (who lives in the Bay Area, like me) recommended 100 deg. I think I’ve always had the wrong egg temperature, and it has been frustrating that there isn’t a definitive number out there. Today, my kitchen in San Francisco was 62 degrees, and I tried Loopy’s 100 deg., which worked, so I took some data from this and used Newton’s Law of Cooling (http://en.wikipedia.org/wiki/Convective_heat_transfer) to develop a model for different room temperature and initial egg temperature scenarios.

The results of the model, and the photos of the cake, are here.

http://flic.kr/s/aHsjuHMjPV

I will be happy to send you the Excel spreadsheet so you play around with it as well. Obviously, the model is only as accurate as my temperature measurements, and this model definitely needs testing. If anyone is making a genoise, please test some of my model’s predictions and report back!

To answer the question of what temperature you should heat your eggs to, you need to find an initial temperature to maximize the amount of time the eggs spend in the 75-80 deg range. If you work out the equation, Newton’s Law of Cooling shows that the time spent in the optimal range is independent of your initial egg temperature. HOWEVER, because the beating time is only 5 min, at moderate room temperatures (62, 70 deg), the eggs don’t have the opportunity to pass through the optimal range within 5 minutes if you use high initial temperatures (110-115), so it is best to use 90 degrees maximize the time spent in the optimal range. At lower room temperatures (40, 50 deg), the times are the same for all initial temperatures examined (90, 100, 110, 115 deg). The model shows that a 70 degree room temp and 90 degree initial egg temp. is the best combination (short of having a room temp at 75-80 degrees). (See the figures.)

If your kitchen temperature is 75-80 degrees, theoretically, you can just heat your eggs to room temperature and then beat. Your eggs would then spend a full 5 minutes in the optimal range. If your kitchen temperature is >80 deg, all you can do is heat your eggs to room temperature and beat. The eggs can never cool below 80 if your room temp is >80. Perhaps you can turn on the AC, if it’s worth it.

STAND MIXER

I’ve tried beating a genoise by hand, and it just doesn’t work well. (It takes 20 minutes, and it strains the wrists.) I’m not sure about a hand-held mixer, but the Newton’s cooling model will probably have to be adjusted for that situation. The model results given above are for 5-minutes at HIGHEST speed beating on a STAND mixer. If you have heated your eggs properly, the foam should fill 1/4 to 1/3 of the 5 qt. KitchenAid mixer bowl. That’s what I observed today, and it looks like Rose gets about the same volume if you look on her videos. You can check yourself at this point. If you don’t have the right volume, then you didn’t heat your eggs properly.

FOLDING

I can’t offer any advice on this, but today my stable egg foam didn’t deflate very much when folding the flour. So fight hard for a stable foam, and also get the Matfer whisk. My batter filled a 9x2 pan half way, which is reasonable. A 9x2 pan is 8 2/3 c. Eggs are 3/4 c, quadrupled to 3 c, then add 1.5 c of dry ingredients and sugar to get 4.5 c. total volume (very rough approximate, assuming no deflation), which is half of the pan. 

OVEN TEMPERATURE:

I calibrated my oven once with an oven thermometer (calibrated in boiling water) and found that it was 2 degrees off at 350 degrees. Today, it was 9 degrees off! So check your oven with a calibrated thermometer EVERY TIME you bake a genoise. Don’t take any chances! If you notice that your genoise takes longer or less than 25 minutes to bake, then your oven temperature is wrong.

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Posted: 26 May 2011 04:23 AM   [ Ignore ]   [ # 1 ]
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Congratulations on your nice and high genoise!!  Enjoyed reading your comprehensive write-up as well.  Glad you had luck with the 100 degrees too : )

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Posted: 26 May 2011 10:18 AM   [ Ignore ]   [ # 2 ]
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Fabulous write-up!

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Posted: 26 May 2011 01:44 PM   [ Ignore ]   [ # 3 ]
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Congratulations on a job well done!!!  Your perserverance is admirable, and you must have learned so much.  Now you can tackle the world of sponge-type cakes with plenty of skill.  smile

Very interesting write-up.  For what it’s worth, I find the two most important variables are having enough egg yolks and getting the folding right.  The folding is quite hard, because there are only a certain number of passes you can make before you have lost optimal height, and if you haven’t mananged to mix everything by then you’ll have pellets (or end up folding more and loose height).

Wow, your work on the temp of the eggs is amazing.  I usually take the lazy man’s route and just think about an average between the egg temp and the air temp.  I know I heat my eggs more in Winter, when the kitchen is cold, than in summer (though I don’t bake nearly as much in the summer, too hot for the oven!).

Your genoise looks wonderful!  Did you end up syruping it?

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Posted: 26 May 2011 05:40 PM   [ Ignore ]   [ # 4 ]
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Awesome.  What a happy day!  You have taken this to a new level.  I often have a very cool kitchen, esp. in winter and I find Italian meringue to be the most amazing… in spite of a cool kitchen it always takes way longer to cool than stated in the recipe.

I would love any tips re: folding.  I have the Matfer whisk but haven’t been able to get great results—in the K5 bowl it’s a tight fit and I find batter collects inside. 

Kudos!

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Posted: 26 May 2011 10:04 PM   [ Ignore ]   [ # 5 ]
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@Sherrie: I’m no expert folder, and I was surprised that my batter didn’t deflate much when I folded in the flour my usual, unprofessional way. So I guess a very stable egg foam offers some protection. Fight hard to get your egg foam stable. (right proportion of yolk to whites, right temperature, exactly 5 min. of beating on highest speed) The Matfer whisk is a little awkward with the K5 bowl. I find that you have to tilt the bowl a little bit to get better contact between batter and whisk. Also, do turn your bowl with each fold. It helps incorporate the flour faster. The batter does collect in the whisk, so shake it out.

@Julie: I’ve been so busy lately, so I didn’t do anything with the genoise actually—just ate in plain with some tea and coffee. I didn’t even want to eat the genoise really. I just wanted to bake it get 1.5 inches. At last, the battle seems over, but I will have to try it again a few more times in the future to make sure that I have this down and also to test my Newton’s cooling model. The strange thing is that it seems intuitive to heat the eggs more in the winter, but according to the physics, it doesn’t matter what temperature you heat your eggs to. For example, if your kitchen is 40 degrees, you can heat your eggs to 90, 100, 110, or 115 degrees. It won’t matter; they all will spend 0.6 min. in the 75-80 degree optimal range. Winter is definitely not a good time to make genoise. 0.6 min. out of 5 min. is only 12% of the beating time. Besides 75-80 deg, 70 degrees is the best room temperature. Again, I’ll need to do some more experiments with genoise to test the model. It would be so helpful to baking if you can determine the exact temperature you need to heat your eggs to just by punching in the room temperature of the day into an Excel program. And then maybe the model can also be applied to other temperature-sensitive operations like mousseline, or if you wanted to know how long it would take to bring a cake up to room temperature, etc.

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Posted: 26 May 2011 10:08 PM   [ Ignore ]   [ # 6 ]
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Michael, Great posting of your work and your rewards are fantastic! An unadorned, picture perfect cake is a thing of beauty. Thanks for sharing all your research and findings. Isn’t Shirley fascinating? I once called her and she advised me about a recipe I could not get to work despite 24 attempts. A normal person would have given up by the 12th or 13th time, but I’m far from normal. At any rate, I took her advice, had success and rewarded her with a dozen cherry muffins I hand delivered to her while she waited for me in the driveway sitting in her Honda Accord. She wouldn’t let me come in bc of her ‘mess’ as she was far behind with the deadline of Bakewise.
Hope your genoise tasted as good as it looked!

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Posted: 27 May 2011 03:50 PM   [ Ignore ]   [ # 7 ]
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M, I’ll be sure to monitor egg temp both before and during whipping with my next genoise.  I’ll report back here.  smile

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Posted: 28 May 2011 02:00 PM   [ Ignore ]   [ # 8 ]
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Michael, great work.
Others have complained about the time it takes to whip eggs by hand and I am puzzled. Last week out of curiosity I timed my hand whisking. I whipped 5 egg whites to soft peak in 2 minutes. I used the bowl from my K5 mixer and eggs straight from the refrigerator. The kitchen was around 65F.

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Posted: 28 May 2011 08:04 PM   [ Ignore ]   [ # 9 ]
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I agree - excellent write-up. Thank you.

Regarding a stable egg foam - a technique I learned a while back is to beat the eggs until they reach maximum volume and just begin to recede. Then, I lower the speed to medium and beat for another 15 minutes. This also helps to stabilize the egg foam. I learned this while reading “Baking and Pastry” from the Culinary Institute of America. I believe it works well.

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Posted: 28 May 2011 10:54 PM   [ Ignore ]   [ # 10 ]
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@Julie: Yes, please do report back next time you make a genoise. If you are going to monitor temperature, you will need to get the room temperature, initial temperature of the eggs, the temperature at a few points during the beating, and the temperature at 5 min. It would be interesting to plot your data and see if it matches the theoretical cooling curve. However, I’m not sure if you can really stop the beating to measure the temperature and then resume again. I know there are all sorts of high-tech thermometers these days that take seconds to get the temperature. I guess it would be ok if you had those. I have really cheap metal coil thermometers that take up to a minute to measure. Anyway, I will check back in August or so. I will be going to Delaware next week and spending the summer there.

@Gene: Egg whites are really easy to beat. I don’t bother to drag out my mixer if it’s just egg whites. The Matfer whisk can make stiff peaks for a few whites in 3-4 minutes. Whole egg foams, on the other hand, take 15-20 minutes for me, and they are too unstable to be used for genoise.

@honeycheese: I’ve read about the long-beating time at medium speed technique in Shirley Corriher’s Bakewise. Shirley cites a lot of sources that advocate this method, which was why I was surprised that Rose tells you to beat for 5 minutes only at highest speed. I’m still not sure how Rose’s method is able to produce a stable foam. Beating at the optimal temperature range is only one factor, but you also need time to create a stable foam. It might be an interesting experiment to try different beating techniques with Rose’s recipe.

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Posted: 28 May 2011 11:30 PM   [ Ignore ]   [ # 11 ]
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michaelnrdx - 29 May 2011 01:54 AM

It might be an interesting experiment to try different beating techniques with Rose’s recipe.

Offbeat techniques? smile

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Posted: 23 November 2011 08:30 PM   [ Ignore ]   [ # 12 ]
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Just read this aloud to my PM basic pastry class and they loved it!

Thanks for your thoroughness - the pastry science dorks of our classroom world are quite happy and content now smile kat

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Posted: 23 November 2011 08:56 PM   [ Ignore ]   [ # 13 ]
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Kit kat - 24 November 2011 12:30 AM

Just read this aloud to my PM basic pastry class and they loved it!

I would be concerned that the students would be intimidated by that.  My experience is that such precision really isn’t necessary in making a genoise.  If the OP found success, I’d bet it had more to do with getting the folding right rather than in finding the perfect temperature.

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