Chocolate Maker's Series Part IV-Modern Conching
Posted by Jeff Stern on August 17, 2017
The conche revolutionized chocolate making by reducing production times and enhancing flavor, texture, and mouthfeel. In most modern conches, the process now takes place in an enclosed chamber that has controlled ventilation, with single or multiple shafts controlling an axis and set of blades for aerating, stirring, mixing and shearing. And in modern conching processes, we now have three stages, called dry, pasty, and wet conching. There are horizontal and vertical conches, and a wide variety of conche designs in use today.
Source: Beckett, Samuel, Industrial Chocolate Manufacture and Use. United Kingdom: Blackwell Publishing, 4th Edition, 2009, p. 205, 207.
The first conches were called longitudinal conches, and were called such because the area holding the chocolate was often shaped like a shell, thus the name conch. Traditionally, a granite roller attached to a moving arm would sweep back and forth over the chocolate mass, constantly moving it and gently creating heat and shear.
Beckett, p 203.
Because it was open to the air, the heat created would help with the evaporation of water, acetic acids, and other "off" flavors. But it did not have the advantages provided by the three stages of conching that take place in a modern conche.
The dry conching stage is called such because dry chocolate flake (see the post on roll refining) is added to the conche, and it is in a dry, not liquid or wet state. The conche is adjusted to toss and aerate the flake in order to drive off any remaining moisture as well as acetic acids and off flavors. Some conches have blades shaped so that when spinning one direction, they will lift and toss the material, and when spinning in an opposite direction, will create more mixing and shearing of the material.
During this first stage, the conche temperature and blade speed can be precisely controlled via an HDMI (computer interface). These conches have a warm and cold water system that provides cooling and heating to the internal wall of the tank. Forced air can be blown through the conche chamber to aid in the evaporation of moisture.
Beckett, p. 199.
As the flake is tossed, the internal wall temperature of the conche can be raised gradually over a fixed period of time, until reaching a maximum temperature
The material will initially take on a crumbly stage and later a pasty stage, similar to peanut butter or nutella. This process needs to be carefully controlled to prevent the formation of agglomerates. Finally, the fat in the chocolate flake will have melted, allowing the fat to flow freely and surround the solids, allowing for lower viscosity. At this point, the wet conching stage begins. Water will no longer be able to escape from the sugar as the particles become coated in fat.
During this stage, the shearing force of the blades through the chocolate will mix and aid in combining the cocoa solids, sugar, and fat. The originally flat particles in the chocolate flake become more rounded, changing the viscosity and flow properties of the chocolate.
The advantages of using a modern conche over simple stone grinders are many. Shorter processing times, better control over viscosity, and more control over flavor development are the main ones.
Lecithin and fat can also be added during different stages of the conching process. We will cover their use in a future post.
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