Pepper mill

A burr mill, or burr grinder, is a mill used to grind hard, small food products between two revolving abrasive surfaces separated by a distance usually set by the user. When the two surfaces are set far apart, the resulting ground material is coarser. When the two surfaces are set closer together, the resulting ground material is finer and smaller. Often, the device includes a revolving screw that pushes the food through. It may be powered electrically or manually.

Burr mills do not heat the ground product by friction as much as do blade grinders ("choppers"), and produce particles of a uniform size determined by the separation between the grinding surfaces.

Food burr mills are usually manufactured for a single purpose: coffee beans, dried peppercorns, coarse salt, spices, or poppy seeds, for example. Coffee mills are usually powered by electric motors; domestic pepper, salt, and spice mills, used to sprinkle a little seasoning on food, are usually operated manually, sometimes by a battery-powered motor.

The uniform particle size achieved using a burr grinder can be desirable for coffee preparation. However, some methods of brewing may be more tolerant of the range of particle sizes produced by a blade grinder; this may be the case for percolated coffee. Regardless, burr coffee grinders are more suited for keeping the flavor and aroma of the coffee beans intact. This is because burr mills produce less heat from friction compared to blade grinders; this is especially important for coffee aficionados looking to get the most flavor from the freshly ground beans, as heat from friction lessens or taints the natural flavor. Burr grinders create less friction and require lower motor speeds, which reduces potential flavor loss due to heat.

Burr grinders obtain these lower speeds through two mechanisms. The lower cost models generally use a small electric motor to drive a series of reduction gears, while better constructed and more costly examples use a larger commercial motor and a belt, with no gear reduction to spin the burrs. The latter example is termed "direct drive". The reduction gear versions are noisier and usually do not have the lifespan of the direct drive units.

Electrical powered burr grinders are available in many variations. Some grinders are "stepped" meaning that they are fixed by the factory into a set series of adjustments while "stepless" varieties use a worm drive or other mechanisms to offer an infinite number of adjustments within their grind range. Other variations include grinders that are equipped with dosers and others that are "doserless". Dosers function as a catch bin to collect the ground coffee and by using a lever, users are able to dose a set amount of coffee. Doserless versions remove the bin and dosing function, and the grinder outputs the ground coffee directly into an espresso machine portafilter or into another container. The doserless examples normally feature additional functions such as weight based or advance time based grinding in order for a barista to grind for an exact amount of grounds required for a specific espresso shot.

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Wikipedia