Making Cacao Paste with Volcanic Stone to Modern Grinders

Cacao paste — also called cacao mass, cacao liquor, or cocoa mass — is the product of grinding roasted cacao nibs until the cocoa butter inside each cell is fully released. It contains only the fat and solids that were inside the bean. At warm temperatures it is a dense liquid. At room temperature it sets into a solid, aromatically tempting block.

Where grinding begins

Take a roasted cacao nib between your fingers and press it. It breaks; dry, a little chalky, with a snap. It smells of something between chocolate and roasted nuts, with a faint sourness underneath from fermentation. Nothing about it suggests it will liquefy.

That transformation is what grinding does. A cacao nib is roughly half fat (cocoa butter), but the fat is locked inside cell walls. The structures that contain the butter survive fermentation, drying, and roasting without releasing it. Grinding is the step that breaks those walls open.

What happens inside the cell, from nib to paste

Inside every cacao nib, cocoa butter sits in fat cells surrounded by a fiber matrix. The cell walls contain the fat so effectively that even though a nib is roughly 50% cocoa butter, it behaves like a dry solid; cracking under pressure instead of melting.

Grinding creates enough friction and pressure to rupture those walls. As the butter releases, it coats the solid cocoa particles and the mass transitions from dry crumbles into a paste. Heat builds during grinding, which keeps the butter fluid. The goal is to break those cell walls as completely as possible and distribute the released fat evenly through the increasingly fine solid particles. This continues until the whole mass becomes smooth, dense, and homogenous.

The target particle size for drinking-grade paste is roughly 15–20 microns. Below 20 microns, the texture registers as smooth on the palate. Above it, a cup of drinking chocolate will feel gritty, even if the drinker cannot name why. A micrometer (a simple device with a tapered trench and size markings) is how grinders check. You put a small dollop of paste on the top, scrape it down the trench, and look at where the particles stop appearing.

Stone grinding, from the metate to the melanger

The physics of releasing fat from cacao by pressing it between two stone surfaces is not new.

The metate — a flat slab of volcanic basalt elevated on three legs, worked with a handheld stone called a mano — has been used in Mesoamerica to grind cacao since at least 5000 BC. Grinding plays a part in our knowledge of cacao consumption history in Western Hemisphere. 

Very early chemical evidence of roasted cacao consumption comes from ceramic vessel residue found at Maya sites in Guatemala and Belize from that period. By the time Spanish colonizers arrived in the 16th century, metate grinding was already deeply established across what is now Guatemala, Mexico, Honduras, and Belize.

The practical challenge of grinding cacao on a metate is the same one every grinder faces: as the butter releases, the mass seizes. The solution, documented in Mesoamerica since at least the 17th century, is to heat the stone. Grinders placed a small container of coals under the metate, which kept the butter mobile enough to work. The principle is the same today as it was then: stone on stone, heat, pressure, and time.

In Guatemala, Mayan women have ground cacao on the metate across generations, with the stone passed down as a functional heirloom. In Antigua, fourth-generation artisans like Chocolate D'Taza still grind cacao by hand on a metate using the same method. The metate is not a museum piece. We see it as the living baseline of a process that modern equipment scaled up.

Leidy of Diego's Chocolate demonstrates the traditional Tz'utujil way of grinding cacao in Guatemala. Photo by author.

The modern equivalent is the stone melanger: two granite wheels rotating on a granite base, applying continuous shear force to the cacao mass as it circulates in the drum. Where a metate requires hours of manual labor per kilo and depends entirely on the person working it, a melanger runs unattended for 24 to 72 hours and processes dozens of kilos at a time. The principle is unchanged — stone on stone, friction generating heat, pressure reducing particles — but the scale and consistency are not.

Melangers also do something a metate cannot easily replicate: as the mass circulates over multiple days, volatile acids produced during fermentation off-gas. This is the step known as "conching." The paste that comes out of a long-running melanger has mellowed in ways a quick grind cannot produce.

What makes a good paste

Particle size and fat retention are the two variables that determine how a paste performs.

At 15–20 microns, paste melts smoothly in hot water or milk. Coarser grinds (30 microns or above) produce a texture most drinkers notice, even if they cannot identify where it's coming from. The target depends on intended use: drinking chocolate and bar chocolate both start from paste but may be ground to slightly different endpoints depending on the application.

Fat retention is what separates cacao paste from cocoa powder. Press the butter out of paste and you get two products: cocoa butter and defatted cocoa powder. Cocoa powder has roughly 10–22% fat; whole paste has around 50%. Ceremonial cacao depends on the fat. Cocoa butter carries fat-soluble flavor compounds, creates the mouthfeel that makes drinking chocolate feel round and full, and allows the paste to emulsify into liquid. A defatted powder cannot replicate that behavior regardless of what is added back.

The other thing grinding cannot repair is what came before it. Paste ground to 15 microns from under-fermented cacao will be astringent and flat. Fermentation quality determines the ceiling that grinding can reach.

How Kampura's cacao becomes paste

Kampura is an organic cacao operation in Izabal, Guatemala that has regenerated former cattle pasture into a productive agroforestry system. This land produces cardamom, sustainable timber, and fine-flavor cacao that is transformed at origin into ceremonial cacao products.

Kampura's control over the cacao runs from the first day of fermentation to the last pass through the grinder. The cacao is grown within the agroforest in Izabal, fermented on-site in wooden boxes, dried in a covered high-tunnel structure, and roasted to Kampura's specifications. Grinding is also done in Guatemala to Kampura's quality parameters: we set all target particle size, fat retention, and batch consistency before any run begins. 

High-quality, ethically-sourced cacao paste is also used as "ceremonial cacao." This is a drink made from pure cacao paste that has been fermented, dried, lightly roasted, and ground. Unlike cocoa powder, it contains the full natural cocoa butter of the bean and is typically melted into hot water or milk to create a rich cacao beverage.

FAQ

What is the difference between cacao paste, cacao mass, cacao liquor, and cocoa mass?

They are all the same ingredient. Cacao paste, cacao mass, and cocoa mass describe the product of grinding roasted cacao nibs until the cocoa butter is fully released and the mass becomes liquid. Chocolate liquor (sometimes written cacao liquor) is the American industry term for the same thing. Despite the name, it contains no alcohol — "liquor" refers to the liquid state the paste takes when warm. Which term appears on a label comes down to regional convention and industry context.

Why does cacao paste taste so bitter?

Bitterness in cacao comes primarily from polyphenols — specifically flavanols — and from theobromine. Well-fermented and properly roasted cacao has had much of its harshest astringency reduced during processing, but the remaining bitterness is intrinsic to the bean. Most ceremonial cacao preparations balance it with honey, cane sugar, or spices.

What is the difference between cacao paste and cocoa powder?

Cocoa powder is what remains after cocoa butter has been pressed out of cacao paste. It typically contains 10–22% fat, versus roughly 50% in whole paste. Because it lacks most of the cocoa butter, it cannot melt into hot liquid the same way paste does, and it carries fewer of the fat-soluble flavor compounds. Ceremonial cacao is made from whole paste because the fat is integral to both its taste and texture.

Can you grind cacao at home?

Yes, with realistic expectations. A high-speed blender or heavy-duty food processor can break down nibs into a rough paste. A small stone melanger (sold for home chocolate making) can reach fine particle sizes given enough time. A traditional metate works with proper technique, much patience and the right stone. None of these will produce paste as fine as commercial equipment, but home-ground paste is functional for drinking chocolate.

Does grinding affect the nutrition of cacao?

The grinding process itself does not meaningfully reduce polyphenol or mineral content. Some volatile flavor compounds can off-gas during long grinding runs, which is partly why experienced grinders monitor the mass over time rather than just setting a timer. Nutritionally, the finished paste is close to the roasted bean it was made from. The bigger variables are fermentation and roasting degree, both of which happen before the grinder is loaded.

What cacao does Kampura use for its paste?

We only use what we grow. Kampura grows cacao in Izabal, Guatemala in a certified organic agroforestry system on land converted from former cattle pasture. 

Learn more

• Chocolate liquor — Wikipedia — The terminology behind cacao paste, cacao mass, and chocolate liquor, and why none of them contain alcohol.
  
  
• Metate — Wikipedia — History and anthropology of the Mesoamerican volcanic grinding stone.
  
  
• The Science of Stone Grinding Cacao — Caldera Cacao Roasters — A bean-to-bar maker's account of the 3–4 day grinding process, particle size measurement, and what over-grinding does to flavor.
  
  
• Watch the Ancient Art of Chocolate-Making — National Geographic — Artisans in Antigua, Guatemala still grinding cacao on the metate.
  
  
• Cocoa Production and Processing — deZaan — Overview of cacao processing from bean to finished products.