Day Five: All good things must come to an end

The last day of the Chocolate Technology course was short, starting with a chocolate troubleshooting session with Ed Seguine, and a long lab session working on tempering and various ways of modifying chocolate. We also did blind testing of a few commercial milk chocolates, attempting to discern what milk “backbone” was used in each product.

Ed Seguine is the VP of R&D at Guittard Chocolate, and is a world-class expert on chocolate. (He wrote the US standard on measuring chocolate viscosity, and has written a tall stack of research papers.) He’s an inspirational speaker, combining an energetic love of chocolate with a limitless depth of knowledge. His first law of understanding chocolate and troubleshooting problems is: “Think Like the Fat.” Crystallized fat makes up the structure of chocolate, and the root of most chocolate confectionary problems is something disturbing this structure. Bloom is the result of liquid fat leaking out of the structure and crystallizing on the surface. Seized chocolate is a result of moisture altering fat crystallization. “Thinking like the fat” is his key to diagnosing problems in the kitchen or factory.

Most of the morning session was spent on small case studies. Some examples:

* How do you deal with chocolate that has been seized to mud by moisture? Consensus: throw it away. Even if you can save it, water presents more problems that just awful texture and viscosity. Chocolate is a super-safe food, because it is very, very dry. Chocolate has so little moisture in it that nothing can really live on it or in it. If you introduce moisture, this inherent safety disappears. Water entering chocolate causes crystallization around droplets, creating little potential microbial islands.

* How do you establish where problems originated when a customer is getting bloomed chocolate? You have to track possible points of temperature variation (what weather has the truck travelled through? has it sat on a loading dock?) Also, having an organized, temperature controlled program to retain samples of every shipped product can help check the status of the product.

The rest of the day was spent in the lab, with part of the class hand tempering, and the rest experimenting with the effects of various processes on chocolate. Some of the modifications that were investigated:

* Denaturing chocolate by overheating. Heating milk chocolate to 200F significantly alters its viscosity. Dark chocolate also changes, but less dramatically.

* Adding water to chocolate. This is quite dramatic. Adding even a very small amount of water to liquid chocolate makes it grainy, and basically turns the mass to a fudgelike consistency.

* Adding lecithin and PGPR to chocolate. Lecithin is a ubiquitous chocolate ingredient, used to lower the viscosity of chocolate without the need to add additional cocoa butter to get the same effect. PGPR (polyglycerol polyricinoleate) also lowers vicosity, but in a different way. To understand the difference, a short detour into “non-newtonian fluids” is needed. Ideally, fluids are just more or less viscous, that is, they are “thicker” or “thinner”, and some fluids do operate this way. Chocolate (and many other fluids) are different, in that they have some resistance to going from rest to motion (called Yield Value), and some resistance to flowing once they are moving (called Plastic Viscosity.) Lecithin and PGPR alter these values very differently. PGPR is used extensively by Hershey’s and other big manfacturers (look on the ingredient label for a Hershey’s Kiss.)

The last activity of the course was to blind taste three commercial milk chocolates, and attempt to discern if they were made with milk crumb, roller dried milk, spray dried milk, or skim milk powder with added anhydrous butter oil. All of these processes produce dried milk, but with different mechanical and temperature stresses. These different stresses produce different flavors and melting textures. The milk crumb chocolate was immediately evident, as it has a very strong caramel flavor from the heating of the milk sugars. Cadbury is famous for milk crumb chocolate. The Guittard chocolate was spray dried, which has buttery kind of flavor with an even melt. Spray-dried milk is the default way of producing dried milk. The third chocolate was a Dove chocolate, which uses a combination of spray dried skim milk powder with added butter oil. The milk flavor in this chocolate emerges later in the melt, and the butter is more evident. The class overall did a good job at correlating tastes with the different milk chocolate processes.

The notes I’ve blogged are hugely incomplete. Spending five days with noted chocolate scientists is a great way to learn how chocolate works, but also how complex this topic can be. I’ve learned a lot of valuable fundamentals, and also learned the several hundred ways that I was messing up my chocolate. I’m looking forward to getting closer to my goal of a really top-class dark chocolate!

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2 Responses to Day Five: All good things must come to an end

  1. Emil says:

    just browsing your blog as I eat cheap Trader Joes Chocolate…

    The discussion about non-newtonian fluids forced me to leave a comment. Your discription of the viscosity of chocolate sounds like a bingham fluid… most common example is ketchup.

  2. tspyz says:

    It’s something close to ketchup, but the difference between the yield and plastic values are not as dramatic as it is in ketchup. Working with the viscometers, we used a Casson model of the fluid, which fit the measured viscosity data to something like 3 9s, which is a pretty darn good model. (I’m not a mech-e, so I don’t know how common it is to have models that fit that tightly.)

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