Slow cooker
From Wikipedia, the free encyclopedia
A slow cooker or crock pot (a trademark often used generically) is a countertop electrical cooking appliance that maintains a relatively low temperature for many hours, allowing unattended cooking of pot roast, stew, and other long-cooking dishes.
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[edit] History
The Naxon Utilities Corporation of Chicago developed the Naxon Beanery All-Purpose Cooker[1]. Rival Industries bought Naxon in 1970, and reintroduced it under the Crock-Pot name in 1971. In 1974, Rival introduced removable stoneware inserts.[2] The brand now belongs to Sunbeam Products, a subsidiary of Jarden Corporation.
[edit] Design
A slow cooker consists of a lidded round or oval cooking pot made of glazed ceramic or porcelain, surrounded by a housing, usually metal, containing a thermostatically controlled electric heating element. The lid is often transparent glass and is not hermetic. The ceramic pot, or a crock pot, acts as both a cooking container and a heat reservoir. Slow cookers come in a variety of sizes, from 500 ml (16 oz) to 7 liters (quarts). 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 slow cookers have two or more temperature settings (eg, low, medium, high, and sometimes a "keep warm" setting). A typical slow cooker operates at (more or less) 80°C (176°F) on low, 90°C (194°F) on high, and 1 hour at 90°C followed by 80°C on medium. Some slow cookers sold in the US in the past several decades did not slow cook at all: all of the settings brought the contents to a full boil, with the only difference in setting being the amount of time to come to a boil. This may have been due to concerns about product liability from unsafe food holding temperatures.[citation needed]
[edit] Operation
Raw food, and a liquid which is predominantly water, such as water, wine, stock, but not oil without water, 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. Cookers often have high and low heat thermostat settings. Some cookers automatically switch from cooking to warming (maintaining the temperature at 62°C–72°C/145°F–165°F,[3]) after a fixed time or after the internal temperature of the food, as determined by a probe, reaches a given goal.
The heating element heats the contents to a steady temperature in the 80–95°C/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.
The liquid transfers heat from the pot walls to the contents, and it also distributes flavours. A lid must be used to prevent warm vapor from escaping, cooling the contents.
[edit] Recipes
Recipes intended for other cooking methods must be modified for slow cookers. Often water must be decreased, as ordinary cooking at higher temperatures requires enough liquid to allow for evaporation, whilst slow cookers prevent vapor loss. Some slow cookers are supplied with recipe booklets; many slow cooker recipes are to be found in cookbooks and on the internet. A small number of cookbooks provide recipes for making 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, timing and recipe adjustments can be successfully made for many recipes not originally intended for these cookers. The long, moist nature of the cooking method gives good results with cheaper (and tougher) cuts of meat.
[edit] Advantages
In a slow cooker, the temperature is low enough to avoid badly overcooking food even if cooked for far longer than necessary. However, success will rely on careful timing, as in all cooking. Meat may become nearly tasteless or "raggy" if overcooked, but the slow cooking process is especially useful to tenderize cheaper cuts. Some foods are better cooked at temperatures below boiling. In particular, the tough connective tissues of meat are broken down without affecting the texture of the meat.
Slow cookers enjoyed a surge of popularity in the 1970s and 1980s, as former housewives joined the workforce and enjoyed the prospect of a hot meal available on returning home from work. The lengthy cooking times allowed them to start dinner cooking before leaving for work. Overnight cooking, utilizing economy rated power, cuts the cost of the meal. For best results, many cooks part-cook root vegetables and sear meat prior to inclusion; then the slow cooker finishes the process of blending flavours, adding convenience and reducing washing up, as this is a "one pot" cooking method.
[edit] Disadvantages
Vitamins and other trace nutrients are lost, particularly from vegetables, partially by enzyme action during cooking. When vegetables are cooked at higher temperatures these enzymes are rapidly denatured and have less time in which to act during cooking. Since slow cookers work at temperatures well below boiling point and do not rapidly denature enzymes, vegetables tend to lose trace nutrients. Blanched vegetables, having been exposed to very hot water, have already had these enzyme rendered largely ineffective, so a blanching or sauteing pre-cook stage will leave more vitamins intact. Green colors are retained better when vegetables are cooked quickly as plant cells are less likely to lose acids.
Kidney beans, and some other beans, contain a toxin, phytohaemagglutinin, which is destroyed by cooking at boiling point but not at the operating temperature of a slow cooker. They become safe to eat after boiling for a minimum of ten minutes, or if they come precooked (ie, in a can). Such precautions must be observed if kidney beans are included in slow cooker recipes, as the relatively low temperatures in a slow cooker will not destroy the toxin adequately, and serious food poisoning may occur.[4] Moreover, kidney beans can be as much as five times more toxic if cooked at 80 °C than if eaten raw, so exposing them to a high temperature for an adequate time prior to slow cooking is vital.
Slow cookers do not typically provide sufficient heat to compensate for frequent additions and removals of food in perpetual stews (pot au feu, olla podrida); 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. Also, removal of the lid lets heat and moisture escape, thus prolonging cooking time and giving microbes the chance to grow.
Like some other kinds of pottery, some slow cookers crocks are glazed with a formula containing lead.[5] Lead is a toxic material when ingested into the body, causing neurological and developmental damage in even small amounts (milligrams or less), and it is not readily cleared from the body, so its dangers do not abate helpfully.
[edit] See also
[edit] References
- ^ photograph at [1]
- ^ Crock Pot brand page
- ^ Faq Answers
- ^ Phytohaemagglutinin, US FDA's Bad Bug Book or Foodborne Pathogenic Microorganisms and Natural Toxins Handbook.
- ^ Cookware Safety - HGIC @ Clemson University
[edit] External links
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