Slow cooker


A slow cooker, also known as a Crock-Pot,
is a countertop electrical cooking appliance that is used for simmering, which requires
maintaining a relatively low temperature, allowing unattended cooking for many hours
of pot roast, stews, soups, “boiled” dinners and other suitable dishes, including dips,
desserts and beverages. History
The Naxon Utilities Corporation of Chicago, under the leadership of Irving Naxon, developed
the Naxon Beanery All-Purpose Cooker. Naxon was inspired by a story his Jewish grandmother
told about how back in her native Lithuanian shtetl, her mother made a stew called cholent,
which took several hours to cook in an oven. The Rival Company bought Naxon in 1970 and
reintroduced it under the Crock-Pot name in 1971. Slow cookers achieved popularity in the US
during the 1970s when many women began to work outside the home. They could start dinner cooking in the morning
before going to work and finish preparing the meal in the evening when they came home. In 1974, Rival introduced removable stoneware
inserts making the appliance easier to clean. The brand now belongs to Sunbeam Products,
a subsidiary of Jarden Corporation. Other brands of this appliance include Hamilton
Beach, West Bend Housewares, GE, Magic Chef, and former American Electric Corporation. Design A basic slow cooker 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 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. Slow cookers come in capacities from 500 ml
to 7 liters. Due to the placement of heating elements,
there is usually a minimum recommended liquid level to avoid uncontrolled local heating. Many slow cookers have two or more heat settings;
some have continuously variable power. Most slow cookers have no temperature control,
and deliver a constant heat to the contents. The temperature of the contents will rise
until it reaches boiling point, at which point the energy goes into gently boiling the liquid
closest to the hot surface. Operation
Raw food and a liquid 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 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 79–93 °C 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 bottom of 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. The most advanced cookers have computerised
timing devices that allow the cooker to be programmed to perform multiple operations
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
Recipes intended for other cooking methods must be modified for slow cookers. Quantities of liquids may have to be adjusted
as there is a 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 and/or
seasonings. 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. They are also often used to cook while no
one is there to care for it, meaning the cook can fill the pot with its ingredients and
come back several hours later to a ready meal. Advantages
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 almost impossible to burn food even if cooked too long; however, some meats and most
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. Disadvantages
Some vitamins and other trace nutrients are lost, particularly from vegetables, partially
by enzyme action during cooking and partially due to heat degradation. 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 enzymes rendered largely ineffective, so a blanching
or sauteing pre-cook stage will leave more vitamins intact. This is often a smaller nutrient loss than
over-boiling and can be lessened to an extent by not removing the lid until the food is
done. Slow cookers do not provide sufficient heat
to compensate for loss of moisture and heat due to frequent removal of the lid, e.g.,
to add and remove food in perpetual stews,. Added ingredients must be given time to cook
before the food can be eaten. If food is allowed to cool below about 70
°C and not reheated, harmful bacterial growth is possible; some bacteria produce toxins
or spores which are not destroyed even by reheating. Hazards
Slow cookers are less dangerous than ovens or stove tops due to the lower temperatures
and closed lids. However, they still contain a large amount
of near-boiling temperature food and liquid and can cause serious scalds if spilled. Raw kidney beans, and to a lesser extent some
other beans, contain the toxin phytohaemagglutinin, which is destroyed by boiling, but not by
the lower temperatures of a slow cooker, so dry beans must be boiled at 100 °C/212 °F
for 30 minutes prior to slow cooking, or alternatively soaked in water overnight, discarding the
water and then boiled for at least 10 minutes. Even a few beans can be toxic, and beans can
be as much as five times more toxic if cooked at 80 °C than if eaten raw, so adequate pre-boiling
is vital. Cases of poisoning by slow-cooked beans have
been published in the UK; poisoning has occurred in the USA but has not been formally reported. This risk can be avoided entirely by using
canned cooked beans, adding them towards the end of the recipe’s cooking time. See also References

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