Slow Cooker

A slow cooker, Crock-Pot (a US trademark that is often used generically), or Slo-Cooker (a UK trade mark that is often used generically) is a countertop electrical cooking appliance that maintains a relatively low temperature compared to other cooking methods (such as baking, boiling, and frying), for many hours allowing unattended cooking of pot roast, stew, and other suitable dishes.

A basic unit consists of a lidded round or oval cooking pot made of glazed ceramic or porcelain, surrounded by a housing, usually metal, containing an electric heating element. The lid is often of transparent glass seated in a groove in the pot edge; condensed vapour collects in the groove and provides a low-pressure seal to the atmosphere. The contents of a crock pot are effectively at atmospheric pressure, despite the water vapor generated inside the pot. A crock pot is quite different from a pressure cooker and presents no danger of an abrupt pressure release.

The ceramic pot, or 'crock', acts as both a cooking container and a heat reservoir. They come in capacities from 500 ml to 7 liters. Due to the placement of heating elements (generally at the bottom and often also partway up the sides), there is usually a minimum recommended liquid level to avoid uncontrolled local heating.

Many cookers have two or more heat settings (e.g., low, medium, high, and sometimes a "keep warm" setting); some have continuously variable temperature. A typical slow cooker is designed to heat food to 170 °F on low, to perhaps 190-200 °F on high. Many recipes that include sauce or liquid will reach the boiling point around the edges, while food in the center remains gently cooked. This may be because slow cooker settings are based on wattage, not temperature.

Raw food and a liquid such as water, wine, or stock are placed in the slow cooker. Some recipes call for pre-heated liquid. The cooker lid is put on and the cooker is switched on. Some cookers automatically switch from cooking to warming (maintaining the temperature at 160–165 °F after a fixed time or after the internal temperature of the food, as determined by a probe, reaches a specified value.

The heating element heats the contents to a steady temperature in the 175–200 °F range. The contents are enclosed by the crock and the lid, and attain an essentially constant temperature. The vapor that is produced at this temperature condenses on the lid and returns as liquid. Some water-soluble vitamins are leached into the liquid.

The liquid transfers heat from the pot walls to its contents, and also distributes flavours. A lid is essential to prevent warm vapour from escaping, taking heat with it and cooling the contents.

Basic cookers, which have only high, medium, low, or keep warm settings, have to be manually turned on and off. Others have settings for high and low (e.g., four hours high, eight hours low) which allow the cook to choose a cooking time after which the cooker switches to "keep warm" mode. The most advanced cookers have computerised timing devices that allow the cooker to be programmed to perform multiple operations (e.g., two hours high, followed by two hours low, followed by warm), and to delay the start of cooking.

Because food stays warm for a long time after switching off, slow cookers can be used to cook food to be taken to be eaten elsewhere without reheating. Some cookers have ways of sealing the lid to prevent the contents from spilling during transport.

Recipes intended for other cooking methods must be modified for slow cookers. Quantities of liquids may to be adjusted as there is little evaporation, but there should be enough liquid to cover the food. Many published recipes for slow cookers are designed primarily for convenience and use few ingredients, often prepared sauces. The long, moist cooking is particularly suitable for tough and cheap cuts of meat—for many slow-cooked dishes these cuts give better results than more expensive ones.

Cheaper cuts of meat with connective tissue and lean muscle fibre are suitable for stewing, and tastier than stews using expensive cuts, as long slow cooking will soften the connective tissue without toughening the muscle. Slow cooking leaves the gelatinised tissue in the meat, so that it may be advantageous to start with a richer liquid.

The low temperature of slow-cooking makes it impossible to burn food even if cooked too long; however, meat and vegetables will become nearly tasteless or "raggy" if overcooked.

Food can be set to slow-cook before leaving for the day, and will be ready on return. Some models include timers or thermostats which bring food to a given temperature, and then lower it. With a timerless cooker it is possible to use an external timer to stop cooking after a set time, or both to start and stop.

Cooking the meal in a single pot reduces washing up, and the low cooking temperature and glazed pot make cleaning easy.