How Is Chocolate Conched? The Step That Sets Texture
Conching is the long, warm stirring step that turns gritty chocolate crumb into a mass that flows and melts cleanly, and it is where most of a chocolate's texture is decided. Rodolphe Lindt invented it in 1879, and a 2019 paper in PNAS by Blanco and colleagues put its main physical job in plain terms: conching turns an inhomogeneous mixture of particulates into a flowing suspension by breaking up aggregates and reducing the friction between particles.
Most writing on the subject treats conching as a flavour ritual and quotes a number of hours as if the number were the point. It is mostly a mechanics problem with a flavour side effect.
What is physically going on inside a conche
After grinding, chocolate is a powder of sugar and cocoa solids held in a limited amount of fat. The Blanco paper describes the particles as sitting in the granular range, roughly 10 to 50 micrometres, with the laboratory crumb having a mean radius of about 10 micrometres and a polydispersity above 150 per cent. That is a jammed solid, not a liquid. It will not pour.
The authors call the fix jamming engineering. Prolonged mechanical action plus the staged addition of dispersants raises the volume fraction at which the mixture jams, so a stiff paste becomes a pourable suspension at the same solids content. Their phrase for it is a solid to liquid transition.
One limitation of that paper. The group ran their rheology on sunflower oil rather than cocoa butter, so they would not have to heat the samples. The jamming physics carries over. The melting behaviour does not.
The three stages, and what each one is for
Industrial conching runs in stages, and a 2024 study in Current Research in Food Science by Guckenbiehl and colleagues gives a worked example at scale. They conched a 60 per cent dark chocolate, built from 45 parts cocoa liquor, 40 parts sugar and 15 parts deodorised cocoa butter, in a 200 kg single-shaft conche.
| Stage | Conditions in that study | What it is doing |
|---|---|---|
| Dry conching | 30 minutes, 50 °C, 500 rpm | Working a powder. Coating particles, driving off moisture and volatile acids |
| Plastic conching | 1200 rpm at 60 °C or 80 °C, sampled hourly from 1 to 6 hours | The stiff phase. Shear is highest here and most of the aroma change happens |
| Liquid conching | Cocoa butter added, then 50 °C and 2400 rpm for 15 minutes forwards and 15 backwards | Thinning to final viscosity |
What conching does to acidity and aroma
Fermented cocoa carries acetic acid, the sharp vinegary note that sits underneath a young chocolate. Guckenbiehl's team measured it across the run and found concentrations from 2590 to 7520 parts per billion, falling throughout conching. Over one to six hours the drop was 42.3 per cent at 80 °C with a pre-charge of fat, 40.1 per cent at 60 °C with backwards rotation, and 31.9 per cent at 60 °C forwards. Without the pre-charge it was 22.7 per cent.
Here is the part the marketing copy leaves out. Conching does not selectively remove the bad notes. In the same study, individual odorants fell by as much as 78.0 per cent in the fat phase, the largest loss being linalool, a floral compound, at 80 °C with pre-charge. Tetramethylpyrazine, a roast-derived note, fell 70.7 per cent under the same conditions and only 10.6 per cent in the gentlest run. Hotter and longer strips out the aroma you wanted along with the acid you did not.
That is why bean-to-bar makers and industrial makers conch so differently. One side is protecting origin character; the other is making a consistent mass from variable beans. For how that split started, see our note on the bean-to-bar movement.
Why the hours quoted on a wrapper mean very little
A conching time is a number with no unit of quality attached. It tells you nothing about shear rate, shaft speed, batch size, fat content at each stage, temperature or rotation direction, and the Guckenbiehl results show all of those changing the outcome at a fixed duration. Six hours at 80 °C with a pre-charge and six at 60 °C forwards without one gave acetic acid losses of 42.3 and 31.9 per cent.
Viscosity behaved the same way. It fell as conching continued, and the batches run without a pre-charge stayed thickest throughout. Duration mattered. Configuration mattered at least as much.
What conching cannot fix
It cannot undo alkalisation. A 2022 review in International Journal of Molecular Sciences by Goya, Kongor and de Pascual-Teresa gathers the figures: Dutch processing has been reported to remove over 60 per cent of total polyphenols, roughly 98 per cent of epicatechin in one study, and theobromine above 20 per cent, rising with the degree of alkalisation. Nothing downstream puts those back. For the longer version, read why Dutch-processed cacao is a different ingredient.
The same review is honest about conching itself being contested. One group reported volatile polyphenols down around 80 per cent during conching; others found no significant change, with variation of about 3 per cent.
Conching also does not set the snap. That is tempering, a separate crystallisation step. Mishra and colleagues, writing in Journal of Food Engineering in 2021, identify form V as the polymorph tempering aims at, and report melting peaks for their own cocoa butter samples at about 32.4 °C and 34.3 to 35.3 °C. Body temperature sits in that window, which is why a well-tempered button goes from solid to liquid on the tongue rather than in the hand.
What is in a Chaski tube
Chaski Cacao is a 600 g tube of 77 per cent dark chocolate buttons, with four buttons as the daily dose stated on the pack. The cacao is single-origin from Peru and Ecuador, from a farm our founder has visited, and it is ground at low temperature. The sweetener is coconut sugar. There are no emulsifiers, no seed oils and no palm oil in it, so no lecithin is doing any of the viscosity work described above, and every batch is tested for lead, cadmium and pesticides.
It also carries Lion's Mane as a fruiting body extract and Cordyceps sinensis mycelium. The Ginkgo Biloba component is being replaced by 200 mg of Tremella fuciformis, a 10:1 fruiting body extract, per daily dose, and tubes are currently in that transition. The button shape changed in mid-2026 with the recipe unchanged. Full ingredient list on the Chaski Cacao product page, and the rest of the library in our guides.
To taste what conching is for, hold a button still on your tongue and do not chew. For how that compares with a drinking preparation, see what ceremonial cacao tastes like.
Frequently Asked Questions
How long is chocolate conched for?
There is no standard. The 2024 Current Research in Food Science study by Guckenbiehl and colleagues ran a 30 minute dry stage at 50 degrees Celsius, a plastic stage sampled hourly from one to six hours, and a 30 minute liquid stage split between forwards and backwards rotation. Commercial figures quoted on wrappers range from a few hours to several days. Because shaft speed, temperature, batch size and fat addition all change the result at a fixed duration, the number of hours on its own tells you very little about the chocolate.
Does conching remove acidity from chocolate?
It reduces acetic acid, which is the vinegary note left by fermentation. In the Guckenbiehl study, acetic acid concentrations ran from 2590 to 7520 parts per billion and fell throughout conching, by 42.3 per cent over one to six hours at 80 degrees Celsius with a fat pre-charge, and by 22.7 per cent without one. The same conditions also stripped other volatiles, with some odorants down by as much as 78.0 per cent in the fat phase. Acid removal and aroma loss happen together.
Is conching the same as tempering?
No. Conching is prolonged mixing that sets flow and aroma. Tempering is a controlled heating and cooling cycle that decides which crystal form the cocoa butter sets into. Mishra and colleagues, in Journal of Food Engineering in 2021, identify form V as the polymorph tempering protocols aim for, and report melting peaks for their cocoa butter samples at about 32.4 degrees Celsius and 34.3 to 35.3 degrees Celsius. Snap, gloss and a clean melt come from tempering. Smoothness and the absence of a vinegar edge come from conching.
Can conching fix badly processed cocoa?
Only within limits. The 2022 International Journal of Molecular Sciences review by Goya, Kongor and de Pascual-Teresa collects figures showing alkalisation removing over 60 per cent of total polyphenols in one study, with roughly 98 per cent of epicatechin lost in another, and theobromine losses above 20 per cent. Conching happens after that and cannot reverse it. The same review notes that studies disagree about conching itself, one reporting volatile polyphenols down about 80 per cent and others finding changes of around 3 per cent.
Sources
- Blanco E, Hodgson DJM, Hermes M, Besseling R, Hunter GL, Chaikin PM, Cates ME, Van Damme I, Poon WCK, Proceedings of the National Academy of Sciences, 2019;116(21):10303–10308
- Guckenbiehl Y, Morales Romero AM, Haug H, Ortner E, Rothkopf I, Schweiggert-Weisz U, Buettner A, Gola S, Current Research in Food Science, 2024;9:100909
- Goya L, Kongor JE, de Pascual-Teresa S, International Journal of Molecular Sciences, 2022;23(22):14365
- Mishra K, Kohler L, Kummer N, Zimmermann S, Ehrengruber S, Kämpf F, Dufour D, Nyström G, Fischer P, Windhab EJ, Journal of Food Engineering, 2021;305:110598