Slow Cooker

A slow cooker, also called a Crock-Pot, is a cooking device consisting of a pot (typically 10 in (25 cm) across and similarly high) made of fired clay and usually glazed, surrounded by a housing, usually metal, containing a thermostatically controlled electric heating element. The ceramic pot, often referred to as a crock, acts as both a cooking container and a heat reservoir. Many slow cookers have two settings for power. Slow cookers have loosely fitting lids (often of glass or similar material) to retain moisture and heat.

Cooking in these appliances is done at atmospheric pressure since the lid is not pressure-tight (and indeed is 'sealed' only by condensed vapors and gravity); thus, as long as liquid (usually water, stock, wine or a mixture) remains in the pot, internal temperatures can go no higher than the boiling point of the fluid (212�F or 100�C for water at sea level). 

The physics of boiling prohibit a temperature of the contents above the boiling point while there is still liquid changing into vapor (most of which condenses back into the crock and so returns moisture to the contents). In this respect, a slow cooker is very different from a pressure cooker, which, though it also cooks using vapor, has both elevated pressures (steam in this case) and temperatures. 

There is some danger of explosion from the increased pressure, which is why maintenance of the pressure relief valve is critical for pressure cookers; in contrast, no correctly used slow cooker can explode since no increase in internal pressure occurs. The outside temperature of a slow cooker can be expected to exceed the boiling point of water to facilitate heat transfer to the crock and to the food.

In use, the food is placed inside the pot and covered with liquid, the lid is applied, and the unit is switched on. Cooking times vary with the recipe and with the food quantity, but are typically several hours. Temperatures are low compared to traditional ovens used for broiling (typically 600° F or 320° C or higher) and baking (typically 300 to 500° F or 150 to 260° C). Cooking is sufficiently slow that, if the food is not removed promptly at the specified time, little harm is done.

The liquid and its proper level is important, for it serves both as the heat conduction mechanism between the pot walls and the food, and as the flavoring (herbs and spices) distribution method and a 'basting' mechanism. No stirring is required (or recommended) since removing the lid during cooking causes significant cooking delays. The lid is important as it prevents escape of hot vapor which would, if permitted, lead to lowering the internal liquid level, loss of heat and drying out of the contents.

Recipes for these cookers must be adjusted to compensate for the nature of the cooking: often water must be decreased. Some come with recipe booklets; many cookbooks with slow cooker recipes are available and there are numerous recipes on the Web. A small number of cookbooks seek to make complete dishes in a slow cooker using fewer than five ingredients while others treat the slow cooker as a serious piece of culinary equipment capable of producing gourmet meals. 

With some experience, timings and recipe adjustments can be successfully made for many recipes not originally intended for these cookers. The long, moist nature of the cooking method allows for lower quality cuts to be used.

Product Name

The slow cooker is also known as a Crock Pot, a registered trademark of Rival Industries, which developed the modern device. The names 'slow cooker' and 'Crock Pot' are used interchangeably in descriptions and recipes, though Rival is the only producer authorized to use the Crock Pot name, and usually protects the trademark so that the term doesn't become a generalized trademark, the way aspirin and cola have.

The 'Crock Pot' name has been licensed to ConAgra by Rival beginning in 2004, when their Banquet frozen food brand introduced a line of prepared frozen meals called Crock Pot Classics, which consist of a full four or five-serving meal packaged and flash frozen by Banquet, then cooked with minimal preparation in a slow cooker. 

The Crock Pot Classics meal kit includes the meat, vegetables, sauces and potatoes needed for preparing the meal; water is the only other item needed. Several varieties, such as stroganoff, beef stew, and chicken and dumplings are available, and a trial coupon for the product is usually included in a new 'Rival Crock Pot'.

Food safety

Using a slow cooker, temperatures are lower than in many other cooking methods, and cooking times are lengthy. Because of this, some people have been concerned about the growth of micro-organisms. Slow cookers are capable of boiling their contents. Boiling is sufficiently hot to cook all meats, including poultry, which requires the highest internal temperature to be safe for consumption. 

If the temperature control mechanism is working correctly, and if food is not left to stand more than briefly at room temperature, there are few problems. Filling the pot, adding water, and then promptly turning on the unit will avoid such problems as well.

If the starting food ingredients are frozen, it may take a long time for the pot to reach proper cooking temperature. During this slow heating, microbes in the food can multiply. The microbes will eventually be killed before the food is served, and so themselves pose little risk. But some microbes produce toxins which remain even after the microbes have died. 

Most such toxins are proteins which are destroyed by the heat of cooking, but some such toxins cannot be destroyed by cooking - for example, botulism toxin. In practice, most such heat resistant toxins, including those that cause botulism, are produced by anaerobic microbes which cannot survive in the presence of atmospheric oxygen. Heat also kills these organisms. As with any cooking technique, when cooking frozen food, do not defrost at room temperature. 

A safer technique is to defrost ingredients in a cold environment, usually a refrigerator, where the temperature is too low for the microbes to thrive. Alternatively, one may defrost foods using a microwave oven so that the bacteria have little time to grow.

Perpetual stews should not be maintained in slow cookers, as slow cookers do not typically provide sufficient heat to compensate for frequent additions and removals of food; nor do they cook quickly enough to cook newly added food thoroughly before the next withdrawal becomes likely. This relatively slow recovery of temperature after an addition or withdrawal may cause safety problems. Removal of the lid lets heat and moisture escape, prolonging cooking time and giving microbes the chance to grow.

Other Hazards

Because these cookers are portable/movable, contain large quantities of hot food and water, and because they are left unattended during long cooking times, they are dangerous around small children and exploratory pets. Cooking areas should be blocked off � effectively � if either might be present without responsible supervision. 

Like all electrical appliances, failures (in the electrical wiring or the control mechanisms) can cause problems, including fires. Although slow cookers have few parts that could fail and reports of their failures are rare, unattended slow cookers should be nonetheless treated with respect and caution. 

For instance, they are best used in a kitchen placed on a tile or similarly reduced flammability surface, and not near flammable materials such as papers or flammable fluids since the outside of the slow cooker does become warm during operation. The fire risk is certainly minimized by isolating the appliance from surrounding flammables.