Well-tempered chocolate

November 21, 2019 4:52 AM

Nina Notman discovers that controlling crystal structures and emulsions is the key to good chocolate.
posted by exogenous (12 comments total)

Somewhere I have a file folder of reprints of chemistry and food science journal articles on the physical chemistry of cocoa butter, particularly concentrating on the thermodynamics of the transitions between the half dozen possible crystalline phases. Because I was a chocolate enthusiast with a chemistry background and newfangled civilian access to the Internet. I tracked down the guy who had authored the comprehensive review articles and asked if he had reprints.

I've made quite a few batches of tempered chocolates, working with up to a kg at a time, and have never used a marble slab. I've always used metal bowls, and slow controlled cooling with lots of stirring. This is basically imitating commercial tempering equipment at bench scale in the kitchen. IDK how much the P Chem influenced my technique but it explained what I was doing, spending all that time stirring. Did I mention there was a lot of stirring?

If you are in North America and thinking about making chocolates for Christmas, it's the time of year when you can order a kg or 6 of couverture and get it delivered to most places without having it melt on the way.
posted by Aardvark Cheeselog at 5:38 AM on November 21, 2019 [1 favorite]

If you are ever in Asheville, North Carolina and wish to learn about this process and more, you can't do better than a stop by the French Broad Chocolates factory. They are dear friends that I worked with for years, from humble beginnings in their house to a growing chocolate empire. The factory is special because all of the machines in the line are in glass walled rooms with video screens and other stuff explaining what is happening. They also do tours and have a classroom for even more education, especially regarding ethical sourcing and many important issues in the often problematic world of cacao.
posted by lazaruslong at 5:59 AM on November 21, 2019 [4 favorites]

Highly related - watch Metafilter favourite Bon Appetit editor Claire Saffitz’s ongoing fight to temper chocolate starting with making her own KitKats.
posted by inflatablekiwi at 6:26 AM on November 21, 2019 [5 favorites]

I've successfully tempered chocolate a few times with this pretty easy method. I've also read that sous vide makes it effortless, but haven't done sous vide myself. It's apropos for holiday baking, as tempered chocolate is much nicer for dipping cookies (say, for your fellow MeFites), etc. Interesting note in the article that, "Tempered chocolate takes several weeks to fully crystallise" -- I'd never heard that! I'd be interested to test the difference between just-tempered vs. tempered and rested chocolate, myself.
posted by daisyace at 9:23 AM on November 21, 2019 [1 favorite]

I met a Russian immigrant years ago, who had run a television picture tube factory back in Moscow. When he came to the U.S., we had already moved beyond CRT technology, and he ended up using his expertise in emulsions to get a job at... a chocolate company.
posted by PhineasGage at 9:47 AM on November 21, 2019 [2 favorites]

The article doesn't say, but makes me wonder. Are the type VI crystals (bloom) just undesirable because they're unsightly? Or is there anything else bad about them?
posted by rikschell at 10:55 AM on November 21, 2019

I've noticed the cocoa butter crystals when I top my rice krispie treats with chocolate. I wondered if I could prevent this.
The way I see it is I can do all that work... or just eat them faster.
posted by Nauip at 11:30 AM on November 21, 2019

Are the type VI crystals (bloom) just undesirable because they're unsightly? Or is there anything else bad about them?

Type VI crystals have a higher melting point, and form macroscopic domains that exclude the cocoa solids that remain emulsified when Type V crystals predominate. Mouthfeel and flavor of the product are both negatively affected.

The densities and mechanical properties of the various crystal phases are also different, leading to things like differential shrinkage of coatings as they anneal.
posted by Aardvark Cheeselog at 12:01 PM on November 21, 2019 [1 favorite]

Since the chef uses a palette knife to handmake glossy chocolate, I wonder if there's a simple way for home cooks to control the crystal size and alignment to glossier tempered chocolate as well? I didn't know about the resting period either, that'd be interesting to see at home as well.
posted by polymodus at 6:19 PM on November 21, 2019

Who knew photographic film and chocolate were so closely linked?
posted by constantinescharity at 9:42 PM on November 21, 2019

I was trying to find a phase diagram for chocolate. This is the best I managed:
http://soft-matter.seas.harvard.edu/index.php/The_Science_of_Chocolate:_interactive_activities_on_phase_transitions,_emulsification,_and_nucleation

There's a temperature dependence, and time-to-form dependence, but I would like to see some pressure or other variables (including ratio of various ingredients). Where can I find a good chocolate phase diagram? (I want to understand why sous-vide should help -- is it just controlling temp more precisely, or is there another reason?)
posted by nat at 11:26 PM on November 21, 2019

watch Metafilter favourite Bon Appetit editor Claire Saffitz’s ongoing fight to temper chocolate starting with making her own KitKats.

Creatively paraphrased from memory: "Damn it do I have to temper chocolate again? Really? I don't want to have to temper chocolate again! BRAAAAAD!"


I've worked with some pro bakers and pastry chefs. If you ask them how they're doing and they say anything like "I have 10 pounds of chocolate to temper" possibly while snarling like a mean dog I highly recommend staying the hell out of their way unless you fancy being ground up and baked into a gingerbread person.
posted by loquacious at 1:42 AM on November 22, 2019 [1 favorite]