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Conching is a process used in the manufacture of chocolate whereby a surface scraping mixer and agitator, known as a conche, evenly distributes cocoa butter within chocolate and may act as a "polisher" of the particles.<ref name=Afoakwa10/> It also promotes flavor development through frictional heat, release of volatiles and acids, and oxidation. The name arises from the shape of the vessels initially used which resembled conch shells.
When ingredients are mixed in this way, sometimes for up to 78 hours, chocolate can be produced with a mild, rich taste. Since the process is so important to the final texture and flavor of chocolate, manufacturers keep the details of their conching process proprietary.<ref name= McClements2007>McClements, D. Julian Understanding and Controlling the Microstructure of Complex Foods, Woodhead Publishing, 2007, Template:ISBN, page 654.</ref>
The conching techique was introduced in Switzerland in the late 19th century. Conched chocolates were distinguished from ordinary chocolates with the French adjective fondant or crémant.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>
HistoryEdit
Rodolphe Lindt invented the conche in Berne, in 1879. It produced chocolate with superior aroma and melting characteristics compared to other processes used at that time. The Lindt chocolate company states that Lindt (perhaps mistakenly) allowed a mixer containing chocolate to run over a weekend (or possibly overnight, according to other variants of the possibly apocryphal story).<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> Upon returning to the device, Lindt recognised the final product to have a smoother texture and greater shine than conventionally processed chocolate of the time. Lindt's invention made the mass-production of chocolate bars more practical, eventually replacing chocolate beverages as the primary means of mass chocolate consumption.<ref name=Talbot09>Talbot, Geoff (ed), Science and Technology of Enrobed and Filled Chocolate, Confectionery and Bakery Products, Woodhead Publishing, 2009, Template:ISBN, chapter 2.5 Conching.</ref> The adoption of conching also generalized the use of additional cocoa butter in the chocolate production; until then, molded chocolate often simply consisted of cocoa mass and sugar.<ref>Template:Cite book</ref>
The original machine used by Lindt was developed in the early 1800s by an Italian chocolatier named Bozelli.<ref>Template:Cite book</ref> The Bozelli grinding process was based on ancient Mesoamerican practices of grinding cocoa beans on curved stones,<ref>Template:Cite journal</ref> which were called metates.
Lindt's original conche consisted of a granite roller and granite trough; such a configuration is now called a "long conche" and can take more than a day to process a tonne of chocolate. The ends of the trough were shaped to allow the chocolate to be thrown back over the roller at the end of each stroke, increasing the surface area exposed to air. A modern rotary conche can process 3 to 10 tonnes of chocolate in less than 12 hours. Modern conches have cooled jacketed vessels containing long mixer shafts with radial arms that press the chocolate against vessel sides. A single machine can carry out all the steps of grinding, mixing, and conching required for small batches of chocolate.Template:Citation needed
The conching process remained mostly a trade secret until the end of the century.<ref>Template:Cite book</ref> In the 1890s, Cailler launched a similar chocolate.<ref>Template:Cite book</ref> A long conche was manufactured by J. M. Lehmann from 1899.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>
ProcessEdit
Conching redistributes the substances from the dry cocoa that create flavor into the fat phase. Air flowing through the conche removes some unwanted acetic, propionic, and butyric acids from the chocolate and reduces moisture. Even a small amount of moisture greatly increases the viscosity of the finished chocolate, so machinery is cleaned with cocoa butter instead of water.<ref name=RKB97>Ranken, M. D.; Kill, R. C.; Baker, C. G. J. (ed.), Food Industries Manual (24th Edition), Springer-Verlag, 1997, Template:ISBN, pages 438–439.</ref> Some of the substances produced in the roasting of cocoa beans are oxidized in the conche, mellowing the flavor of the product.
The temperature of the conche is controlled and varies for different types of chocolate. Generally, higher temperature leads to a shorter required processing time. Temperature varies from around Template:Convert for milk chocolate to up to Template:Convert for dark chocolate. The elevated temperature leads to a partially caramelized flavor and in milk chocolate promotes the Maillard reaction.<ref name=Afoakwa10>Emmanuel Ohene Afoakwa, Chocolate Science and Technology, John Wiley and Sons, 2010, Template:ISBN, pages 43, 65–66.</ref>
The chocolate passes through three phases during conching. In the dry phase the material is in powdery form, and the mixing coats the particles with fat. Air movement through the conche removes some moisture and volatile substances, which may give an acidic note to the flavor. Moisture balance affects the flavor and texture of the finished product because, after the particles are coated with fat, moisture and volatile chemicals are less likely to escape.<ref name=Talbot09/>
In the pasty phase more of the particles are coated with the fats from the cocoa. The power required to turn the conche shafts increases at this step.
The final liquid phase allows minor adjustment to the viscosity of the finished product by addition of fats and emulsifiers, depending on the intended use of the chocolate.
While most conches are batch-process machines, continuous-flow conches separate the stages with weirs, over which the product travels through separate parts of the machine.<ref name=Talbot09/> A continuous conche can reduce the conching time for milk chocolate to as little as four hours.<ref name=RKB97/>
After conching is completed, the flavor continues to change as it tastes increasingly acidic.Template:Sfnp
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