Adventures in Tempering

August 16, 2007

I’m finally getting the bulk of the last two batches, one milk and one dark tempered and ready to send to the crew of guinea pigs that have volunteered to sample some of my early work. I’m learning a great deal about tempering in this process. One lesson is that all thermometers are not made equal. I’ve been using a pistol-style laser thermometer for the last few tempers, which has worked out quite nicely. It only reads the surface temperature, but that seems to be perfectly adequate for tempering, and lets me shoot temperature readings without needing to clean a probe. My wife was kind enough to buy me a fancy probe thermometer, which I thought would be better. The chocolate didn’t feel right at the temps that the probe was supplying, and, indeed, it didn’t temper correctly. I’ll need to calibrate this one if I want to use it in the future.

Wilhelm Wanders of Chocolaterie Wanders in the DC area sent some useful tips about controlling the cooling process after the tempered chocolate is poured. The cooling process determines what the final gloss on the chocolate is going to look like. I’m at the stage where I’m worrying about the temper, so have occasionally thrown the poured chocolate into the freezer to get it to set up correctly. This yields some really funny surfaces and is not recommended. This last batch I let cool at room temperature (at least room temperature on an August night that started at about 76 degrees and fell to 55 or so overnight) and got a very nice result, at least in the batch of dark chocolate that I tempered. Here’s the result after setting up overnight:

Tempered dark chocolate

(Yes, I need to splurge on some bar molds…)

The surface that the chocolate cools on makes a big difference to the final look of the chocolate also. This cooled on aluminum foil that was flattened to the extent I could by hand, and the foil side of this chocolate is mirror smooth. Pro shops will use acetates (this is also how they get printed designs on chocolate), which also yields a super shiny surface. Sort of cheating, but I’m willing to experiment at this point.

Now, the milk chocolate was a different story. I used nearly exactly the same hand tempering process, heating the chocolate to ~115F, cooling to 91F, mushing 20% of the chocolate on chilled marble, then remixing and bringing the mixture to 86F or so. This is milk chocolate, so the melt temperatures I was using are about 2-3 degrees lower than the dark. Here’s the chocolate after the pour, at about 83F:

83F milk chocolate

It’s super shiny, and starting to set up. About an hour later, it’s close to room temperature, about 76F. Still got a good shine, and it’s getting reasonably solid.

setup tempered milk chocolate

Astute observers will note the sample taken from the upper left corner for scientific purposes. I went to bed feeling pretty good about this result, unaware of the nasty surprise awaiting me in the morning:

bloomed milk

Yikes! This is nearly the same result that I got when cooling the chocolate in the freezer. It happened instantly in the freezer, and just took longer this time. I can’t tell if this is straightforward bloom on the chocolate or if some ingredient is reacting badly. The cream power I used had an anti-caking agent in it, so perhaps that accounts for this odd behavior. This was setting up on parchment paper, and the parchment paper side shows some quite pleasant marble patterns:

parchment patterns

I could pretend that I did this on purpose, but this is pure accident. Any chocolate brains out there have any hints on why the milk chocolate might be reacting this way?

The Mysteries of Chocolate Tempering

July 5, 2007

So, the short version of this post is that attempt #2 at tempering milk chocolate worked! The long version, well……tempering chocolate is still a deep, dark mystery to me. The basic idea here is that the fat in chocolate can take (depending on who you talk to) five or six crystalline structures, all of which have different properties. The types, I-IV, increase in stability and melting point as you move up the scale. Type I crystals, for example, melt at 17.3C (63F), and are only stable enough to exist for a few minutes before migrating to Type II crystals, which mely at a higher point. All chocolate is, to some degree, doing this crystalline morphing until it hits the Type VI crystal, which melts at 97F, and has a waxy mouthfeel. Tempering attempts to convert the majority of the crystals in the chocolate to Type V crystals, which melt just below body temperature, are stable enough to stick around for months, and contract when cooled. This contraction makes it possible to mold chocolate and extract it from the mold.

This sounds simple, but there are a number of complicating factors, none of which I completely understand yet. First, most chocolate, even when it seems solid, in fact has a lot of liquid chocolate trapped in the fat matrix. You want to keep some of this liquid chocolate around, or otherwise you end up with “overtempered” chocolate. Second, the size of the crystals in this matrix determine if you get shiny chocolate or not. Crystal size is determined by how you treat the chocolate after tempering. Cool it too fast, and you can get bloom. Cool it too slowly, you get big crystals and no shininess. Third, the surface that it is cooling in makes a difference. Cool it against glass or plastic and you get a smooth, shiny surface. A rough surface will eliminate shine.

So, the last batch of chocolate I made was a milk chocolate, which complicates this even further by introducing milk fat into the mix, which interferes with crystallization (making the chocolate soft, which is good.) Tempering milk chocolate requires working a few degrees cooler than working dark chocolate. My first attempt to temper this chocolate resulted in this:

Poor temper on milk chocolate

The chocolate has no shine at all, is soft at room temperature, and has a sandy texture you can see on the breaks. I was working on too warm a surface, so the needed seed crystals never formed. Interestingly enough, chocolate can be shiny and not bloomed even when it’s not tempered. Here’s some chocolate from the exact same batch, poured directly into a Pyrex dish from the melangeur and cooled at room temperature for a day. The dents are my fingerprints, showing that this chocolate is soft and melts well below body temperature. However, note that it has a good shine, and after a day, is showing no signs of bloom. I have no idea what crystal forms are present here.

Shiny but untempered milk chocolate

At 120F, we’ve melted all of the crystal forms and can start again. The poor initial temper hasn’t damaged the chocolate at all. Here’s what that dull, untempered chocolate looks like when remelted. It’s a nice, thick, shiny chocolate. (And, as my wife will attest, quite tasty!)

Melted milk chocolate

Working with a slightly chilled stone (about 70F), I was able to create some good seed crystals and get the whole mass tempered using the mush method. After cooling overnight, here’s the result:

Tempered milk chocolate

It’s somewhat shinier, though i cooled this in a pan lined with parchment paper, so the surface is somewhat rough. I also made the mistake of putting it in the freezer for a few minutes as it was setting up, causing instant streaking on the surface from overly rapid cooling. (Note to chocolatiers: rapid cooling produces an actually quite pleasant wood-grain looking set of streaks through the chocolate. This could conceivably be used to intentionally create a rather nice, although unconventional, look on some chocolates.) However, this has a uniform texture and set up quickly. It’s tempered, but it’s not a great job.

In contrast, here’s an untempered piece that was slowly cooled in the refrigerator on a smooth plastic surface. It’s got a nice shine to it. Next batch, I just need to get the proper tempering technique together with the proper cooling technique.

Shiny milk chocolate

Also, clearly I need to be doing more library work on exactly how the liquid and solid phases of the chocolate are interacting, and generally getting a better framework for thinking about the multiple processes going on here. (Yes, I could buy a tempering machine, but every chocolatier I talk to insists that having a complete understanding of tempering is critical, if for no other reason than debugging things that go wrong, and judging how to improve results.)

Batch 10 – It’s Milk Chocolate!

July 1, 2007

Given that my first attempt a few months ago to make milk chocolate ended with something like grainy chocolate-colored Play-Doh, I was a little nervous about starting this batch. To successfully make milk chocolate, you need to get a lot of solid ingredients, including a lot more sugar, to flow in a nice liquid, or the melangeur simply won’t work. This means more heat, and adding some cocao butter (and perhaps, gulp, lecithin) to make the mixture flow enough to refine. For some reason, I also decided to make this my biggest batch ever, at over five pounds of chocolate. I followed the method of crushing the nibs to chocolate liquor in the melangeur, since I need to spend time melting cocoa butter and combining the dairy ingredients. The trick to making everything flow was to add cocoa butter, then sugar, then dairy, heat the mixture with a hair dryer, then repeat. The cocoa butter, melted to a liquid at 140F, does an amazingly good job of making the whole mass flow. It took almost an hour to get 1.1kg of sugar, over .5kg of cream powder and dried milk, and the cocoa butter worked into the crushed nibs. Here’s what the mass looked like with everything incorporated:

Unrefined milk chocolate

It’s grainy, and the mixture breaks at the top of the melangeur wheel. Tasting, it has a bunch of sequential, unblended tastes. Looking carefully, you can also see individual cocoa solids as black specks in the lighter overall mass. This mass, more viscous than the dark chocolate I’ve built before, also stablizes at a higher temperature. Dark chocolate runs in the melangeur at around 105-110F, this mass is running at 120-125F with no external heat added. Ideally, I’d like to it to be at 130F, but I don’t have an easy way to continually dump heat into the melangeur yet.

After 18 hours of refining, here’s what’s in the melangeur right now:

Milk chocolate nearly done

This is now a very smooth, flowing milk chocolate. It’s about two degrees cooler than it was running yesterday, indicating that it’s thinner with some refining. Preliminary taste testing shows a very clean milk taste with a nice cocoa note. The usual fruitiness of the Ocumare cacao is not easy to pick out underneath all that sugar and milk, but it’s definitely present in a sort of freshness to the taste. I’m going to let this run for another few hours, then it’s tempering time. I won’t age this, as I want to keep the dairy notes clean and distinct.

Batch 10 — Making Milk Chocolate

June 29, 2007

Time to go off the reservation and make some milk chocolate. This is partially a technical exercise, but also I want to build a baseline batch to start modifying into a very dark, vary high cacao content milk chocolate. Think of it as a gateway drug from milk to single origin dark chocolate!

The ingredients here will be:

  • Non-fat dried milk
  • Cream powder (72% milkfat)
  • Sugar
  • Vanilla Extract
  • Salt (this is a Terry Richardson derived recipe, and he’s big on salt in milk chocolate!)
  • Ocumare Criollo Cacao
  • Cocoa Butter

This is a big step from the previous batches of dark chocolate, which were only two ingredients — cacao and sugar. There will need to be more consistency control, since it’s going to be harder to get the refiner to work with all that dry milk and sugar!

The net inputs will be about 1.1kg cacao + cocoa butter, 1.0 kg sugar, and 0.6 kg dried milk + cream powder, bringing it to about 40% cacao content. The cacao will be roasted on a long 25 minute low temp (60C) dry cycle, then a 10 min 100C harder roast. I may extend the last roast cycle depending on how the nibs are turning out.

The Quest for Milk Chocolate

June 20, 2007

As heretical as this notion is to some choco-philes, in addition to working on building a really good dark chocolate, I’m preparing to work on some batches of milk chocolate. It’s significantly more complex, since the process moves from basically two ingredients for dark chocolate (chocolate liquor, which is roasted, ground cacao nibs; and sugar), to at least four for milk (cacao mass, sugar, some form of dried milk, and cocoa butter to control texture.) Controlling texture is much harder, and the materials are harder to source. Cacao beans will last a long, long time in dried form, so are easy to store. Milk products are much less stable, and harder to come by.

To complicate matters, there are at least five different milk foundations that can be used to make milk chocolate. Since milk is mostly water, you need to get that water out before mixing it into chocolate. You also have to control for the amount of milk fat. In general, more milk fat yields a softer chocolate. The methods for getting milk and chocolate compatible are:

  • Milk crumb, which is made by heating condensed milk, adding sugar and some chocolate liquor, then heating the whole mass in a vacuum oven. This partially cooks the milk, resulting in the classic Cadbury caramel notes.
  • Spray dried whole milk. This is what the majority of milk chocolate is made from. If you take milk, and atomize it into a low presure, dry container, it loses moisture and becomes a powder.
  • Roller dried whole milk. You can also dry milk via making it a film on a hot roller. The pressure and cooking here will yield a certain amount of cheesiness in the chocolate. This is a less efficient process, so not used much anymore.
  • Dried skim milk plus anhydrous milk fat (AMF). By removing the milk fat from the milk, and separately removing the moisture, you can get more control over the milk fat content in the chocolate.
  • Cream powder. Yes, you can also spray dry cream! This yields a powder that can be around 75% milkfat, and yields an amazingly silky milk chocolate. In my opinion, this is the Cadillac of milk chocolates. Dried skim milk can also be added.

The sugar, chocolate liquor, and milk product all need to go through the refining and conching process, as they all need to get coated in thin layers of cocoa butter and have their particle size reduced so that the chocolate is smooth.

I’m aiming to mess with making a high-cacao content cream powder milk chocolate. The next step is finding cream powder in sub-semi truckload quantities. I seem to have found one source and am pursuing options with some local dairy suppliers. More milk chocolate progress updates coming later…

The Mysteries of Roasting

June 19, 2007

The three big processes that determine the flavor of chocolate are fermentation, roasting, and conching. These are the steps where the art of chocolate making really lies, and also the steps that seem to be the least understood in the scientific literature on chocolate. Fermentation has to happen nearly immediately after the cacao pod is harvested from the tree, so is a hard variable to control for, unless you are a huge chocolate company, or a committed chocolatier willing to spend part of your year on a plantation like Steve DeVries. Perhaps some day I’ll be able to experiment with this process, but for now, I have to content myself with tweaking roast and conching to develop chocolate flavor.

S. Beckett’s encyclopedic tome “Industrial Chocolate: Manufacture and Use,” despite it’s forbidding title, actually has some interesting clues for small batch producers. Buried in section 5.8, R.F.M. Heemskerk mentions two interesting studies that sound like good jumping off points for tweaking my next batch. The first is a study by Zeigleder and Oberparleiter in 1996: “Aromaentwicklung in Kakao. Auswirkung der feucht-thermischen Behandlung.” The upshot of this study is that steaming nibs to add about 15% water, then doing a slow pre-roast at 40-60C to reduce the moisture, followed by a full roast at 98-100C develops more cocoa flavor precursors, and yields a chocolate with a more intense taste. Having water present seems to facilitate the sugar/amino acid reactions that form chocolate flavor during the roast. This is yet another scientist proposing using water, chocolate’s natural enemy!

The other study mentioned by Heemskerk is Mohr, et. al., 1978, in “Uber die Grundlagen der Aromaveredelung von milchfreien und milchhaltigen Shokoladen-massen.” The finding here is that optimal development of chocolate flavor is accomplished by a slow pre-roast, lowering moisture in the cacao bean to about 3% before rapidly increasing the temperature to the final roast temperature.

Both of these ideas seem simple enough to try, though it’s going to be an incredible pain to build some parallel batches to compare the taste of the final product under different roast conditions if I’m going to go all the way to completed chocolate.

Like Water for Chocolate?

June 5, 2007

Artisan chocolate, made by hand, with exacting attention to the cacao bean is what motivates this blog. At the same time, it’s fascinating to look at how far science and industrial production can drive the frontiers of chocolate. Chocolate making is a gigantic industry, and like any gigantic industry, there are millions of dollars poured into advanced research and development, all with the hope of gaining some competitive edge.

Side Note: For a peek into how brutal the candy industry is at the top levels, check out Joel Glenn Brenner’s “The Emperors of Chocolate“, which details the rivalry between Hershey’s and Mars. It’s a 35 year old slugfest that makes Coke vs. Pepsi look like 3rd graders squabbling in a playground. Even more remarkably, Mars and Hershey’s used to work together closely, with Hershey’s supplying raw chocolate to Mars. As a side effect, while the first M in M&M’s stands for Mars, the second stands for Murrie, the president of Hershey’s at the time!

Patent 7,186,425, just issued on March 7th, shows how this kind of research can turn centuries of technique upside down. In traditional chocolate making, rule #1 is “water is the enemy.” Even a small amount of moisture in chocolate can render it lumpy, granular, and can make it sieze up, destroying machinery. Almost every step of the conventional chocolate making process is about driving out moisture, and the end product has less than 1% water. This patent shows how, paradoxially, to make chocolate that contains up to 30% water! The motivation is to create a lower calorie chocolate that can also contain nutrients that are only water soluble. The trick seems to be to premake chocolate, then very gently mix in a suspension of water in oil (using lecithin or PGPR to emulsify.) The mixture keeps the water from forming a continuous phase, preventing it from affecting the cocoa fat matrix and screwing up the chocolate. Various other inventors have proposed processes for this trick, but none have gotten to this level of water content.

According to the patent, with proper handling through the conching process, and careful tempering, this watery chocolate will form bars with classic chocolate texture that will not bloom for a long time. The primary inventor of this process is S.T. Beckett, the author of the encyclopedic “Industrial Chocolate: Manufacture and Use” and the introductory “Science of Chocolate.”

I don’t think I’ll be heading to the store for any watery chocolate anytime soon, but I have to admire the pure mad scientist aspect of this technique!