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January 8, 2006
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Engineers hope their chocolate conching system can simplify the process and encourage gourmet chocolatiers to engage in automated processing.

Harry Way, technical director, Netzsch Fine Particle Technology, Exton, PA.
Chocolate making is a process shrouded in mystique, where art seems to trump science, at least in terms of understanding. Engineering holds it is more chemistry than alchemy, and engineers in South America and North America have developed a compact conching system and quantified processes to produce chocolate of the intelligent designer's choice.



Brazil's Flavio Abaurre, owner of Meller SA, developed a distinctive conch and integrated it with a ball mill from the German firm Netzsch Fein Mahltechnik GmbH to create a compact, enclosed system that accelerates the process of making couverture and chocolate bars and provides a means for specialty confectioners to automatically create gourmet chocolates. In the last two years, Abaurre has worked closely with the Netzsch Fine Particle Technology division in Exton, PA, to refine the system and improve batch repeatability. Fabrication of systems that can output 53,000 lbs. of commodities such as milk chocolate is proposed, a commercial scale that would compete with high-shear mixers and other equipment designed to accelerate mass production. But compact units to produce high-end couverture and bars can turn artisans into small-scale chocolate manufacturers.

Directing the US collaboration is Netzsch Technical Director Harry Way, who holds a BS degree in mechanical engineering from the University of Pittsburgh. He has been involved with Netzsch's R&D lab since joining the company 21 years ago.

FE: How did Netzsch's partnership with Meller SA of Brazil come about?

Way: (Owner) Flavio Abaurre's firm makes sugar-free chocolate. He's also a mechanical engineer who builds melters and other cocoa and chocolate equipment. About four years ago he used our ball mill in a system he was integrating. It worked really well, and that led to the engineering collaboration for the system we call ChocoEasy.

A number of systems have been built for manufacturers in Brazil. Based on the success, we struck an agreement two years ago, where he markets the system in South America and we market in North America and Europe, where our parent company was founded in 1873. We've built two commercial systems for Europe since April.



Netzsch Engineer Jonathan Nicol loads the raw materials of chocolate into a conch designed to accelerate the process. Small batch sizes and compact design bring chocolate manufacture within the reach of a new category of processors. Source: Netzsch Fine Particle Technology.
FE: How does the system differ from other chocolate machinery?

Way: Traditionally, manufacturers mix the sugar, vanilla and other ingredients, grind them to a small particle size, then do a dry conch with cocoa butter and cocoa liquor, followed by a wet conch. It's a long process that typically requires big and expensive machines and high labor costs.

Flavio rethought the process to come up with a method that combines wet conching and grinding in one step. The chemical reaction between the ingredient components occurs quickly in part because we're able to screen out the fines when the ingredients are recirculated through the ball mill. If we eliminate fine particles early in the process, we reduce the amount of cocoa butter 1%-5% and accelerate the process. The largest particles that are left are smaller than is typically found, so the overall size distribution is much more narrow than with conventional processes. That's what nanotechnology is all about.

FE: Is it primarily a matter of finer milling, then?

Way: The conch itself also is a departure. Besides its compact size, the moisture removal that occurs is more efficient. Typically, hot air blows across the surface of the liquid to remove water during wet conching. We have tubes directed into the mixture to blow 65?C air (149°F) down into the mass, with enough air volume to create bubbles in the mixture. The whole scheme is much better. Why didn't anyone do it this way before? I don't know, but as far as we can tell, no one has.

FE: By accelerating the process, are some essential chemical reactions between the ingredients short-circuited?

Way: In the wet conching step, grinding and chemical reactions between the components are occurring, and the chemical reactions occur quickly. Once all the materials are brought together, modern technology figures out ways to make the particles react more quickly while also getting rid of the off flavors.

FE: Some major confectioners incorporate continuous conching with high-shear mixing to accelerate production. Does that trump your chocolate process?

Way: I don't think you can get the same quality with a continuous conching process. You have to drive off the aromatics that are generated, and I don't see how continuous conching removes undesirable elements such as moisture and volatiles.

FE: For gourmet chocolate, what particle size is desirable?

Way: They are below 20 microns, compared to 30 to 40 microns for conventional chocolate. The smaller the particles, the smoother the product. By recirculating the ingredients for an extended period, makers of gourmet dark and white chocolate can avoid using soya lecithin and other emulsifiers and still achieve very smooth texture. This system shortens the recirculation time significantly.

The process parameters are the same as with coarser grinds, but the time spent recirculating the material is greater, and perhaps there is a larger pumping motor, which typically runs as fast as possible. The industry's most common measurement of particle size is with a micrometer, with maybe nine measurements. We're able to grind to 13 microns, so we use a light scattering method for measurement. The very tight size distribution of particles also means high quality.

FE: Why are you able to combine wet conching and refining in the penultimate process step?

Way: Disk mill agitation is the key. The rotor spins at relatively high speed, so the energy density is much greater than with conventional mills. We use small grinding balls, and we're not regrinding the small particles. If you recirculate the chocolate, you want to do it as quickly as possible and allow homogenization to occur quickly. Instead of taking 72 hours to make a gourmet chocolate, we're talking about a conch time of four hours.

FE: Does the mill differ from units you fabricate for paint and other applications?

Way: There are some geometrical changes and slight modifications to the agitator, but it's a fixed design. Every installation is tweaked to the user's specific needs, of course.

Chefs and chocolatiers who knew how to make confections but hadn't manufactured chocolate before accounted for our first two-dozen installations. A PLC manages the recipes and controls time and temperature and other aspects of production automatically. It's basically a one-button operation.

FE: How cocoa fats and solids achieve a particular flavor and texture remains a mystery. How can an engineered system quantify those dimensions?

Way: We can't quantify flavor and texture, but we can quantify the operating parameters and take the mystery of duplication out of it. We can measure moisture content, we can quantify time and temperature. A lot of variables affect the finished product; we're reducing those variables and quantifying the speed of agitation, the number and size of the balls in the mill and other parameters so that once the recipe is set, the equipment can recreate it.

Knowing how different aspects of the raw materials impact the finished product is something that traditionally wasn't well understood and made chocolate making an art. Nobody checked the moisture content, for example, but an article I found by a German chemist named Franke demonstrates moisture's affect on crystallization of the sugar. Science is enhancing understanding of the process.

FE: What barriers exist for the chocolate purchaser who wants to become a manufacturer?

Way: One of the biggest problems in the US is the raw materials supply: people who make cocoa butter and cocoa liquor don't want to sell in lot sizes under 1,000 lbs., which basically is a pallet load. If lots could be broken down further, it would encourage more people to consider these systems. There's also the mindset that you've got to make 4 million lbs. a year if you're going to make your own chocolate. We have to make believers out of people that this is feasible, and it can be done in a small space. Our 300 kg batch unit only requires three to four square meters of floor space-about 9 by 12 feet. We're building an even smaller system that only produces 100 lbs. a day.

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