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Home , Chocolate, Chocolate liquor, Conching, Dark chocolate, Milk chocolate

Mysteries of Revealed Conching plays an imperative role in the development of and is crucial to the success of a smooth, well-balanced end product.

Carly Meck Blommer Chocolate Company

rom the discovery of the ing chocolate had a smooth texture, mild Fthousands of years ago to the irreplace- flavor and improved viscosity. This led to able treat the world knows today, chocolate more development on a machine known as has been an integral part of our lives. To bet- a longitudinal conche (Figure 1). This ter understand the transformation of choco- machine, shaped somewhat like its namesake late over the years, it is important to explore shell, consisted of a heavy roller repeatedly an important step in the chocolate making moving through a basin filled with liquid process called conching. During conching, chocolate. By adding a small amount of refined ingredients are kneaded under to the thick chocolate mass, the roller is able to glide easily through the basin Carly Meck is senior R&D immense force to create a smooth, well-bal- scientist — product and create a uniform product. While years anced end product. Conching has been development at Blom- shrouded in some mystery over the years. of technological advancements have since mer Chocolate Co. In Looking at what takes place during this step improved the process, this breakthrough was this role, she develops a game changer for the chocolate industry. new chocolate and sheds some light on this important process. cocoa formulas, creates Conching has a long and accidental his- CONCHING STYLES process improvements, tory with chocolate. Until the mid-1800s, All conches are not created equal. Func- provides training and chocolate was mostly consumed in beverage executes technical stud- tionality differences exist between styles form while a few pioneers introduced it into ies. She has been with along with differences in price, cycle time the company since 2010. baked goods. Solid chocolate was not a pop- and floor space requirements. Essentially ular treat due to its coarse texture and unde- all systems perform the same task of knead- sirable sour and bitter flavor. Rudolphe ing chocolate; however, each uses a different changed this in 1879 by inventing the method of doing so. The principle conching conche in . There is no clear story methods or styles are illustrated in Figure 2. on how his invention came to be, but it allegedly happened by accident while leaving Longitudinal Conche a mixer on over a long weekend. The result- As shown in Figure 1 and 2A, the longitu- ➤

72nd PMCA Production Conference, 2018 1 Mysteries of Conching Revealed

The concept behind Longitudinal Conche this style of conche today, but it is not as the melanger is based common as other methods. on the centuries-old mortar and pestle. It Melanger can be used for The concept behind the melanger is based several different on the centuries-old mortar and pestle. It functions including can be used for several different functions grinding nibs into including grinding nibs into liquor and liquor and making making butters. For the purposes of chocolate making, nut butters. it is a refiner conch. The melanger uses Figure 1 Brooklyncacao.com rotating stone wheels which grind the mass dinal conche was where it all began. These against a stone-bottomed bowl reducing conches create improved flavor develop- particle size of the raw materials while ment and texture of the chocolate, but simultaneously conching (Figure 2B). cycle times can be restrictive, often taking All of the ingredients are added at the days to conche a mass. Limitations of this beginning of the process resulting in high conche method include difficulty in filling content while grinding over several and emptying and in temperature control. hours. Significant particle size reduction Formulation can also be a challenge. Com- can be achieved (down to 25 microns); pared to other styles, paste fat is very high however, cycle times can exceed 24 hours. in this machine type, therefore chocolate As with the longitudinal conche, paste is conched in a liquid phase. A higher fat fat is quite high so the ability to eliminate content in the conche equates to less volatiles or moisture is minimal. Melangers cocoa butter savings at the end of the are ideal for smaller confectioners; initial process. Several chocolate makers still use cost is low, and the machine footprint is

Conching Styles

2A. Longitudinal Conche 2B. Melanger 2C. All-in-One or Rotary-Style Refiner Conche

2D. Ball Mill Refiner Conche 2E. Continuous Conche 2F. High-Shear Conche Figure 2 ➤

2 72nd PMCA Production Conference, 2018 Mysteries of Conching Revealed small. Furthermore, a significant produc- smaller size footprint. As with the other In some systems, tivity advantage for confectioners is that styles of refiner conches, cycle times and ingredients such as melangers are able to complete several throughput can be a challenge along with cocoa butter or conching steps at once. the higher amount of cocoa butter needed can be dosed to standardize viscosity. as the chocolate All-in-One Conche or Refiner Conche advances through the All-in-one conches, or refiner conches, have Continuous Conche system. gained popularity over the years. A more Continuous conches use a different mech- sophisticated version of the melanger, the anism to treat chocolate than the afore- refiner conche reduces particle size and mentioned styles. With this style, refined conches within the same machine. Forced chocolate is fed through the machine which air can help drive off volatiles, reduce cycle applies intense mixing for a short period time and improve the flavor of the finished of time through a jacketed rotor/stator product. The principal theory behind this (Figure 2E). Shearing and mixing are machine is based off high fat, or liquid applied to the chocolate in one step while conching. That being said, there are several pushing the mass through a temperature- styles of this equipment type. controlled cylinder. In some systems, ingre- The traditional style of refiner conche dients such as cocoa butter or lecithin can consists of a water-jacketed horizontal be dosed as the chocolate advances tank. Ingredients are added and a series through the system. Benefits to this style of angled metal knives scrape the ingredi- of machine are fast cycle times and homog- ents against a grooved metal inner wall enized product in a matter of minutes. Dis- while rotating around a center axis (Fig- advantages are lack of volatile removal ure 2C). Variable pressure can be applied and fat release. A few systems pair the con- to achieve the desired particle size. These tinuous conche with other machinery conches take up minimal floor space and which aids in the removal of volatiles and consume less than other types and moisture before the chocolate is conched. the cost is reasonable for the throughput. High-Shear Conche Drawbacks to refiner conches include long process times and the potential for using High-shear conches are a specific category more cocoa butter for the desired final vis- of equipment based on the theory of low- cosity due to super fine particles formed fat conching. Low-fat conching results in while grinding. the maximum efficacy of moisture and volatile reduction, particle rounding due Ball Mill Refiner Conche to shear, fat release and flavor enhance- A newer style of refiner conche consists of ment. Unlike the other conche styles, these a conche trough attached to a ball mill. The machines run in conjunction with a roll- ingredients are conched first, sometimes refining line. In this process, refined using forced hot air in the temperature-con- is conveyed into the conche. A small trolled trough. After conching, product is amount of cocoa butter is added to create recirculated through a ball mill (Figure 2D) a thick paste. Target fat percentage of the to achieve the desired particle size. Extra refined flake is 22 to 25 percent while the cocoa butter or emulsifiers are added during target fat percentage of the conche is 27 this step as the chocolate thickens and par- to 30 percent. The conches are able to use ticle size is reduced. This all-in-one unit is a specialized paddle design to kneed the another cost-effective option and has a chocolate more efficiently. A wedge- ➤

72nd PMCA Production Conference, 2018 3 Mysteries of Conching Revealed

Milk shaped blade at the end of the paddle mov- Three-shaft high-shear conches have typically reach ing in one direction allows the blade to cut intense mixing capabilities that tend to temperatures into the chocolate mass and thoroughly bring the product into a plastic or pasty between 55° C and mix the product (Figure 2F). This step phase quite quickly. Three interlocked pad- 65° C. This allows for occurs first during conching at high rpm. dles move the mass from one end of the flavor development Next, the conche paddles switch direction unit to the other while continuously expos- without risking the creating intense shear at high rpm scraping ing the product to air to help eliminate the mass between the wedge-shaped pad- creation of scorched volatiles and moisture. About halfway dle and the conche wall. . through the cycle, the paddles automati- During the entire conching process, tem- cally change direction facilitating further peratures are closely controlled through shearing action. Cost, power consumption chilled water flow in the jacket. choco- and footprint make three-shaft systems a lates typically reach temperatures between restrictive option, however this may be 55° C and 65° C. This allows for flavor devel- outweighed by their ability to produce a opment without risking the creation of premium chocolate product. scorched flavors. Dark chocolates can reach temperatures ranging from 70° C to 90° C THREE STAGES OF CONCHING depending on product and cycle time. TRANSFORM CHOCOLATEXXX Different styles of machines exist within Conching occurs in the middle of the the high-shear conche realm (Figure 3). chocolate-making process. While the Two-shaft conches are typically designed conche does wonders to transform choco- to hold the dry phase longer than other late in various ways, the upstream and styles. The paddle design of the two-shaft downstream processes can also have an conche allows for independent movement effect on the final product. After dried around the machine with more paddles cocoa beans arrive at a processing facility, driving sheering action against the walls. shells are removed and the nibs are roasted Louvres at the top of the machine can be to develop a deep chocolate flavor and to opened or closed. Opening allows for mois- ensure a reduction in their microbiological ture and volatiles to be eliminated while load. The nibs are next milled into liquid closing during liquefying contains splatter. then , cocoa butter Capacity of these machines is typically and, potentially, milk powder are mixed quite large, as are the footprint and energy together to form a thick paste as seen in requirement. As with any model of high- the conching steps in Figure 4. This paste shear conche, cost can be prohibitive. How- is sent through a pre-refiner and subse- ever, full automation of these machines quent five-roll refiners to reduce particle makes them a user-friendly option. size to a desired specification and produce a dry flake. Other forms of particle size Two-Shaft versus Three-Shaft High-Shear Conches reduction could be used as well. The flake is added to a conche with a small amount of cocoa butter to create a thick paste to be kneaded. After conching, the product is liquefied with an emulsifier and stabi- lized to a specific viscosity using cocoa but-

Two-Shaft High-Shear Conche Three-Shaft High-Shear Conche ter. The product can then be tempered and Figure 3 deposited into its desired form. ➤

4 72nd PMCA Production Conference, 2018 Mysteries of Conching Revealed

Conching Stages the chocolate from the conche it must be Simply from the acrid Chocolate is transformed during three dis- liquefied. This is accomplished using an odor observed tinct stages of the conching cycle (Fig- emulsifier, cocoa butter or a combination through open louvres ure 5). The dry phase, plastic/pasty phase of the two. Cocoa butter can then be dosed while a conche is and liquid phase are common terms asso- in order to achieve the desired viscosity running, it is evident ciated with these chocolate conching steps. for the application. After the chocolate is that volatiles are This section will specifically apply to high- liquefied, limited further flavor enhance- driven off during the ment and volatile removal occurs. shear conches which are quite common in conching process. chocolate manufacturing. These three steps occur at different The dry phase begins while the conche times during the conching cycle and no is being filled with chocolate flake and is two recipes are typically the same. Milk Steps in making crucial to help reduce some of the excess chocolate conche cycles can last anywhere chocolate moisture. By continuously mixing the flake from 6 to 16 hours while at a controlled temperature and exposing can exceed 20 hours, depending on the sys- it to air near the louvres, moisture and tem. Dark chocolate cycle times are typi- unwanted volatiles are removed. This cally longer due to the increased chocolate removal is easier to accomplish earlier liquor portion of the formula. Unless the while particles are not fully bound in fat. liquor has been pretreated, a longer cycle The second plastic/pasty phase begins time will help eliminate unwanted volatile Refiner Paste once the conche is filled and additional molecules and produce a less bitter and cocoa butter has been added to help form sour chocolate. a thick paste. The goal of this step is to hold CONCHING BENEFITS the chocolate in this thick paste for as long as possible. By holding the paste in this Reducing Volatiles phase, the intense shear and heat begin to Several studies over the years have shown s release any bound fat and coat the other that volatile organic compounds (voc ) Dry Flake particles in the matrix. Just as in the dry are reduced over time during conching. phase, unwanted volatile molecules are The majority of volatiles being driven off driven off. The plastic/pasty phase is also are which is inherent in choco- responsible for additional flavor enhance- late from the fermentation process. One ment by means of flavor transfer between study shows that 30 percent of the concen- molecules which will be explained later. tration of acetic acid can be driven off by The last phase of the conche cycle is the conching while another study indicates that Conche Paste liquid phase. In order to properly evacuate 57 percent of overall volatiles can be Figure 4

Conching Stages

Dry Phase Plastic/Pasty Phase Liquid Phase Figure 5 ➤

72nd PMCA Production Conference, 2018 5 Mysteries of Conching Revealed

The majority of decreased. Simply from the acrid odor Average Results of Hourly PID Readings volatiles are released observed through open louvres while a of Volatiles Exiting a Conche during the filling and conche is running, it is evident that volatiles dry conching phase are driven off during the conching process. when the mass is To demonstrate and quantify the timing thick, the temperature of volatiles exiting the conche, the author conducted a study of headspace volatiles is elevated and the during conching. A photoionization detector energy input is high. (PID) was used to measure the total VOCs exiting the conche. Various recipes of dark and were tested hourly in a production setting while a dark chocolate Figure 6 made in a tabletop melanger was also stud- cent during conching. This reduction in mois- ied. An average of the results is shown in ture causes the product to have an improved Figure 6. as well. In addition to the release As expected, the majority of volatiles of free fat, the moisture reduction helps thin are released during the filling and dry the chocolate. conching phase when the mass is thick, the temperature is elevated and the energy Improving Texture and input is high. Dark chocolate had a higher Although particle size is not reduced in volatile output due to the increased choco- traditional conches (excluding refiner late liquor portion of the formula. Even conches or melangers), sharp edges are though a dark chocolate formula was made rounded off creating the illusion of finer in the melanger, hardly any volatiles were particles and a superior mouthfeel. A driven off during the cycle. recent study analyzing particle shape and size through the use of an environmental Reducing Moisture scanning electron microscope showed Moisture is driven off in small amounts conched chocolate particles to be more during conching, particularly during filling round in shape and less densely packed and dry conching. Interestingly, this hap- into their crystalline network compared pens at temperatures below the boiling to samples taken early in the chocolate point of water. Water removal occurs as making process. This is shown in Figure 7. the chocolate mass is continually mixed Another aspect of texture improvement Particle Shape and Size and exposed to the surrounding air. from conching is in fat distribution within Ensuring proper filling rate enables the the chocolate matrix. By releasing the fat moisture to be driven off in adequate bound in refining, particles will contain an time. Filling the conche too quickly can even fat distribution which helps them to to grit or agglomeration if the mois- better glide across a consumer’s palate. ture is not removed. Having any louvres Pre-refined Particles or ventilation open on the conche during Improving Flow Characteristics this process aids in moisture removal. Conching has the ability to release fat that Chocolate is fundamentally a low moisture has been encapsulated during the refining . Since chocolate and water are not mis- process. A properly conched mass will yield cible, any reduction in moisture content will a thinner chocolate once stabilized. To

Conched Particles yield a better finished product. Beckett sug- demonstrate the effect that conching has Figure 7 gests that moisture can be reduced by 30 per- on viscosity reduction, the author con- ➤

6 72nd PMCA Production Conference, 2018 Mysteries of Conching Revealed ducted an experiment using a 400 lb, high- strated that a longer conche cycle does not Numerous scientific shear conche to make milk and dark necessarily mean a superior product. It studies over the years chocolate. Samples were taken at 2-hour should be noted that these are shortened have attempted to intervals and stabilized to a targeted vis- cycle times compared to production identify the cosity. Figure 8 indicates the amount of machines and the data is not directly trans- mechanism behind added cocoa butter needed to stabilize latable. Chocolate formulation, conche flavor improvement samples to the specification. While this is style and processing constraints should also occurring during only a small study to quantify viscosity be taken into account when determining conching, and some reduction, released fat is a proven charac- a cycle time for optimum flavor enhance- of the results teristic of a well-conched chocolate. This ment. Figure 9 displays a spider graph of contradict one viscosity improvement ultimately to an unconched dark chocolate verses a dark another. cost savings in end product since less cocoa chocolate in a 22-hour conche cycle eval- butter is needed to standardize the choco- uated by a trained sensory panel. late. This study also demonstrates that Another factor of flavor enhancement there is a plateau in viscosity improvement. is the redistribution of those flavors over Enhancing Flavors various molecules. By collecting cocoa but- ter from the mass using a centrifuge before Flavor enhancement is another benefit of and after conching, a gas-chromatography conching, but it seems to be the least under- and mass spectrometry analysis was carried stood. Numerous scientific studies over the out to determine overall volatile com- years have attempted to identify the mech- pound content. It was discovered that a anism behind flavor improvement occur- ring during conching, and some of the significant portion of the flavor volatiles results contradict one another. To observe surrounding the fat and cocoa molecules how flavor improves over time, the author Flavor Change on Unconched versus conducted an experiment in a 400 lb, high- Conched Dark Chocolate shear conche. Samples of milk and dark chocolate were taken at 2-hour intervals during a 10-hour conche cycle and stan- dardized to the same viscosity. The samples were then evaluated by a trained chocolate sensory panel. While some preferences dif- fered, the majority felt that the flavor of the milk chocolate stopped improving after 6 hours while the flavor of the dark choco- late stopped improving at 8 hours. This small-sample experiment demon- Figure 9

Amount of Added Cocoa Butter Needed to Stabilize Milk and Dark Chocolate

Figure 8 ➤

72nd PMCA Production Conference, 2018 7 Mysteries of Conching Revealed

There is no perfect transferred to the sugar molecules during Flavor Distribution Before and way to conche the course of the conche cycle. All - After Conching chocolate. Every cules present in the mass then contained method has positives similar flavor levels which lead to a well- and negatives rounded chocolate flavor profile with a associated with it, be decreased sweetness perception as indi- it from a cost, energy, cated in Figure 10. cycle time or flavor Malliard reaction may be responsible perspective. for some of the flavor development in milk chocolate but research on this is limited. The temperatures in milk chocolate conch- ing would likely be too low to deliver much Figure 10 flavor change. However, if any flavor devel- opment or browning did occur from the That being said, chocolate transforms in a Malliard reaction, it would be between the unique way inside a conche. Moisture is reducing , i.e., lactose and free amino reduced, volatiles are removed, flavor is acid groups. enhanced, viscosity is lowered and mouth- feel is improved —all within one machine. Harnessing Chocolate Supplier There is still much to learn about the Knowledge to Fit Application aspects of conching and the mechanisms As mentioned earlier, there is an optimum by which it alters chocolate. n cycle time for viscosity reduction as well as for flavor development. It is up to the REFERENCES time-tested expertise of the chocolate man- Albak, F., and A.R. Tekin. “Variation of Total ufacturer to find the ideal cycle time for Aroma and Content of Dark flavor delivery while maximizing the avail- Chocolate During Three Phase of Conching.” Journal of Food Science and Technology, vol. able free fat for each individual formula- 53, no. 1, 2015, pp. 848–855., doi:10.1007/s tion. This would not only save on energy 13197-015-2036-4. usage to produce the product, but on cycle Beckett, S.T., et al. Becketts Industrial Chocolate Manufacture and Use. John Wiley & Sons time as well since many varieties of Inc., 2017. conches are batch processes. Beckett, S.T. The Science of Chocolate. RSC, Certain recipes may require a longer cycle 2011. Glicerina, Virginia, et al. “The Influence of Dif- time and will likely cost more due to ingre- ferent Processing Stages on Particle Size, dient requirements such as a high cocoa Microstructure, and Appearance of Dark mass dark chocolate. On the other hand, Chocolate.” Journal of Food Science, vol. 79, no. 7, Mar. 2014, doi:10.1111/1750-3841.12508. some may be quite short, such as a milk Hoskin, Jeanne M., and Paul S. Dimick. chocolate with a low developed milk flavor “Volatile Fatty Acid Changes During the Conching of Chocolate.” 33rd PMCA Pro- profile. Work with your chocolate supplier duction Conference. 1979. to select a chocolate that is right for your Muntener, Kurt. “Conching: Back to Basics.” product line, customer base and price range. 64th PMCA Production Conference. 2010.

CONCLUSION There is no perfect way to conche choco- late. Every method has positives and neg- atives associated with it, be it from a cost, energy, cycle time or flavor perspective. ➤

8 72nd PMCA Production Conference, 2018 Mysteries of Conching Revealed

Questions and Answers Q: At what point in the process is work with every recipe but some flavor added? Specifically, how is might have that flexibility. If you are Q: Can the volatiles be recycled extract added (in regard to working with a refiner conche, a and used for chocolate flavors and moisture)? step you could take would be to how? A: It depends on the conche sys- increase the forced hot air flow or A: Theoretically they could but I tem used but in the vast majority of widen the range of particle size tar- don’t know of anyone who is doing cases, vanilla extract is added in sta- get. As with any cycle time reduc- this in practice. There are over 400 bilizing which is the very last step of tion, a trial should be conducted to flavor molecules in chocolate, many the process. This is after the product ensure the change does not have of which are undesirable (i.e., acetic is refined and conched. Since any negative side effects to the final acid). To select, segregate, and bot- vanilla extract has such a high alco- chocolate product. tle a few individual flavor molecules hol content, you would want to add would likely cost more than it it when the chocolate is thinned Q: How does the addition of would be worth. out and cooled down to avoid lecithin in paste mixing affect roll flashing off the flavor. Adding this refining and conching? Q: Can you briefly discuss conche A: In some cases, lecithin can aid in optimization techniques? before the conching step would result in driving off this flavoring in the refining of a product. Care A: There are a few things you could should be taken to minimize any do. If we are talking about high-shear the form of volatiles,which would lead to very expensive waste. lecithin needed as this will affect conches, which are very common in conching. Adding lecithin too early the chocolate manufacturing indus- Q: How many different conche in the process can do one of two try, it is important to have the proper times and processes is it feasible for things. 1) it could start to liquefy the target fat percentages at the different a manufacturer to have? chocolate before it has a chance to stages of the process. If the flake con- A: The various conche times would fully conche and 2) it could denature tains too much fat when entering be seemingly endless. If you have under the high heat and cause you the conche, then little shearing an automatic system, your pro- to need more emulsifier or cocoa action will occur. Additionally, if the gramming would need to have butter to standardize to viscosity. fat is too low, then the proper flavor enough space for the different development will not occur. Other recipes but that is essentially your Q: How does particle size and dis- steps can be taken like increasing the only roadblock. Each individual tribution affect fat release and vis- temperatures slightly which could chocolate formulation should have cosity reduction? help reduce the cycle time. Many a separate conche recipe to maxi- A: Particle size will always affect the styles of conches have the ability to mize the available free fat and flavor viscosity of a product in terms of report out data during the conching development. Conche recipes and any additional cocoa butter needed process in the form of a graph which processes are not one size fits all and to achieve a desired viscosity. A contains valuable information such really depend on the flavor, smaller particle size will need more as temperature and amps. This is a throughput and cycle time you cocoa butter to standardize to the tool you can use to make sure the need to achieve. same viscosity than a larger particle conche is running efficiency for each size. individual formulation. Q: How do you determine optimal conching time? Trial and error? Are Q: What causes grit if a conche is Q: Have you utilized pulling a par- there ways to decrease conche time precharged with butter and tial vacuum on a conche to more or increase throughput? bypasses the dry and plastic phases? precisely control volatile removal A: Trial and error is a good method A: Grit, or agglomeration, will be and reduce conching time? to begin with when you are first caused by moisture in most cases A: I haven’t specifically tried this, starting up. Once you have several with the exception of severely but in theory, it could be a good recipes established, then any new burnt/scorched product. When by- technique (and there might be formulations can be offshoots of passing the dry and plastic phases, some folks out there in the industry those existing recipes. Each type of moisture does not have a chance to currently doing this). You do want conche would have a way to escape from the chocolate matrix to be careful not to remove too reduce cycle time. In a high-shear before it is enveloped in fat. many volatiles or you will have a fla- system, for instance, you could vorless chocolate. increase the temperature slightly to reduce the cycle time. This won’t ➤

72nd PMCA Production Conference, 2018 9 Mysteries of Conching Revealed

Q: Can you describe the impact of increasing particle size on conching? A: The larger the particle size, the less surface area. This correlates to less time needed to fully envelope the particles in fat from the matrix. This would lead to a shorter cycle time but you have to consider any negative sensory affects that coarse particles would have for a product. Q: What leads to the release of cocoa butter during plastic phase? A: During high-shear conching, heat and shear/friction lead to the release of fat. By controlling the fat percentages during refining and dry conching, you can maximize the ability of the machine to release all of that bound fat. If the incoming flake contains too high of a fat con- tent, then the product will immedi- ately start to liquefy in the conche and little release of any bound fat will be seen. Q: Why isn’t more moisture and organic acids driven off in roasting rather than doing this in a conche? Moisture and organic acids are driven off in great numbers from cocoa beans or nibs in the roasting process. However, the resulting chocolate liquor still has a sour and bitter flavor. Some systems exist that can pretreat the chocolate liquor before conching by means of thin film evaporation. This would help to eliminate moisture as well as volatiles (with the added benefit of reducing conche cycle times). The conching process helps to alleviate moisture from other adja- cent processes. Milk powder, for instance, can contain 3 to 4 percent moisture so this must be removed from the chocolate as well.

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