Why Crush Spices Instead of Chopping Them? Cells Opened by Force

Aromatic compounds in spices, herbs and garlic are held inside cells and in small structures within the tissue, and getting them out requires rupturing those structures. A blade cuts through tissue, opening the cells it passes through and leaving the rest intact. Crushing applies pressure across a whole mass, bursting cells throughout, smearing their contents together and mixing them as it goes. The result is a far more complete release and a genuine combination of what has been released, which is why a paste made this way tastes different from the same ingredients chopped and stirred together. Heat is also relevant, since a fast-spinning blade warms the material and drives off the most volatile compounds first.

The choice of material determines what the tool is good for:

• •Granite and other rough stone, heavy with a coarse surface that grips
• •Marble, smooth and handsome and comparatively poor at holding material
• •Wood, light and absorbent, which takes on flavours permanently
• •Ceramic, with a deliberately unglazed rough interior
• •Brass and bronze, used traditionally in several regions for spices
• •Volcanic rock, porous and rough, used across Mexico and Indonesia

A paste made by pounding has a specific quality that machines produce badly, and cooks who use both notice it immediately. Pounding breaks material down unevenly, leaving a range of particle sizes rather than the uniform slurry a blade produces, and that variation gives a paste body and a texture that coats rather than runs. Fibrous ingredients such as lemongrass and ginger are crushed and separated into fibres rather than chopped into pieces, which releases their content without leaving chips of tough tissue. Emulsions form more readily, which is why sauces built on garlic and oil are traditionally made this way. And the cook can stop at any stage, judging by feel, which a machine does not allow.

Comparing the tool with its electric replacements shows what each is actually for rather than settling which is better. A blade grinder chops repeatedly at high speed, producing an uneven result and warming the material, which suits dry spices in quantity and handles wet pastes poorly. A burr grinder crushes between two surfaces at a set gap, which is genuinely closer in principle and produces a consistent particle size, and it is the right tool for coffee and for large quantities of dry spice. A food processor chops, which gives a watery result with herbs because the cells are cut rather than crushed. A powerful blender with a small jug comes closest for wet pastes and still cannot be stopped and assessed the way a hand tool can.

The technique looks self-explanatory and is not, and using it badly is why many people abandon the tool. The motion is a firm press and twist against the side rather than a hammering from above, since grinding does the work and pounding mostly makes noise. Material is added in small quantities rather than all at once, working each addition down before adding more. Hard items are broken first and softer ones added later, with the order mattering considerably in a paste of several ingredients. Salt is added as an abrasive, which is the single most useful piece of advice, since it grips slippery material and grinds it. A new stone tool is seasoned by grinding rice to remove loose grit.

Crushing bursts cells throughout a mass and mixes what they release, while a blade opens only the cells it passes through and warms the material as it spins. Stone, ceramic, wood and volcanic rock each suit different work. Uneven particle sizes give pastes body, fibrous ingredients are separated rather than chopped, and salt added as an abrasive is the single most useful technique.