A slow cooker, also known as a crock-pot (after a trademark owned by Sunbeam Products but sometimes used generically in Australia, South Africa, Canada, New Zealand, the United Kingdom and the United States), is a countertop electrical cooking appliance used to simmer at a lower temperature than other cooking methods, such as baking, boiling, and frying. This facilitates unattended cooking for many hours of dishes that would otherwise be boiled: pot roast, soups, stews and other dishes (including beverages, desserts and dips). A wide variety of dishes can be prepared in slow cookers, including ones typically made quickly, such as bread.
Slow Cooker 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 itself is often made of glass, and 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 vapour generated inside the pot. A slow cooker is quite different from a pressure cooker and presents no danger of an abrupt pressure release.
The “crock,” or ceramic pot, itself acts as both a cooking container and a heat reservoir. Slow cookers come in capacities from 500 ml (17 US fl oz) to 7 litres (7.4 US qt). Because the heating elements are generally located at the bottom and often also partway up the sides, most slow cookers have a minimum recommended liquid level to avoid uncontrolled heating. Some newer models have coated aluminum or steel “crocks” which, while not as efficient as ceramic at retaining heat, does allow for quicker heating and cooling as well as the ability to use the “crock” on the stove top to brown meat prior to cooking.
Many slow cookers have two or more heat settings (e.g., low, medium, high, and sometimes a “keep warm” setting); some have continuously variable power. In the past, most slow cookers had no temperature control and deliver a constant heat to the contents. The temperature of the contents rises until it reaches boiling point, at which point the energy goes into gently boiling the liquid closest to the hot surface. At a lower setting, it may just simmer at a temperature below the boiling point. While many basic slow cookers still operate in this manner, newer models have computerized controls for precise temperature control, delayed cooking starts and even control via a computer or mobile device acquiring Naxon’s 1940 patent for the bean simmer cooker. Rival asked inventor Robert Glen Martin, from Boonville, Missouri, to develop Naxon’s bean cooker into a large scale production model which could cook an entire family meal, going further than just cooking a bean meal. Martin also designed and produced the mass-making machines for Rival’s manufacturing line of the Crock-Pot. The cooker was then reintroduced under the name “Crock-Pot” in 1971. Slow cookers achieved popularity 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 Cuisinart, GE, and KitchenAid.
Operating a Slow Cooker
To use a slow cooker, the cook places raw food and a liquid, such as stock, water, or wine, in the slow cooker. Some recipes call for pre-heated liquid. The cook puts the lid on the slow cooker and turns it on. Some cookers automatically switch from cooking to warming, maintaining the temperature at 71–74 °C (160–165 °F) after a fixed time or after the internal temperature of the food, as determined by a probe, reaches a specified value.
Heating element heats the contents to a steady temperature in the 79–93 °C (174–199 °F) range. The contents are enclosed by the crock and the lid, and attain an essentially constant temperature. The vapour that is produced at this temperature condenses on the bottom of the lid and returns as liquid, into which some water-soluble vitamins are leached.
The liquid transfers heat from the pot walls to its contents, and also distributes flavours. The slow cooker’s lid is essential to prevent the warm vapour from escaping, taking heat with it and cooling the contents.
Basic cookers, which have only high, medium, low, or keep warm settings, must be turned on and off manually. More advanced cookers have computerized timing devices that let a cook program the cooker 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 cooked in a slow cooker stays warm for a long time after it is switched off, people can use the slow cookers to take food elsewhere to eat without reheating. Some slow cookers have lids that seal to prevent their contents from spilling during transport.
- Cheaper cuts of meat with connective tissue and lean muscle fibres are suitable for stewing, and produce tastier stews than those using expensive cuts, as long slow cooking softens connective tissue without toughening the muscle. Slow cooking leaves gelatinous 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; even food that has been cooked too long. However, some meats and most vegetables become nearly tasteless or “raggy” if over-cooked.
- Food can be set to slow-cook before leaving for the day so it is ready on return. Many homeowners with rooftop solar panels switch to slow cooking because it draws under 1 kW of power and can therefore be powered entirely by 1-2 kW panels during the day. Some models include timers or thermostats that 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 water waste resulting from cleaning multiple dishes, and the low cooking temperature and glazed pot make cleaning easier than conventional high-heat pots.
- 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 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 leaves 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, (pot-au-feu, olla podrida). Added ingredients must be given time to cook before the food can be eaten.
- Because of the longer cooking time, there is greater danger with slow cookers of having an extended power outage during cooking without the cook’s knowledge; for example, the power may go out for several hours while the cook is away at work in places with unreliable power supply.
Buying a Slow Cooker
Everything you need to know about choosing the best one-pot meal-maker.
Slow cookers are a relatively cheap and convenient way to get healthy home-cooked meals with minimal effort. A good one will allow your meal to develop that rich flavour you can’t get any other way. And they’re not just for hearty winter meals – in summer, the slow cooker can make a pot roast or one-pot meal without heating up your kitchen like an oven.
Do I need a slow cooker?
A slow cooker is a convenient and versatile addition to your kitchen. They cook food using moisture such as soups, casseroles and stews, at relatively low temperatures with correspondingly long cooking times (several hours). They’re also great for soups with meat and chicken, and any type of legume such as lentils or pulses.
Slow cookers are ideal because they:
- can be left unattended
- cook inexpensive cuts of meat, retaining natural juices
- make less mess
- don’t require stirring
- don’t produce that much heat in the kitchen and can be used all year round.
However, slow cookers may not suit everyone because they:
- require longer cooking time
- are bulky to store
- can be disrupted by a power failure
- may require extra cooking steps (certain foods may need to be cooked on a stovetop first to enhance their flavour, such as browning meats, cooking onions and garlic or frying curry pastes/powders).
How big should my slow cooker be?
- If you’re cooking for two, you’ll only need a 3-4.5L slow cooker
- If you’re cooking for a group, look at a 5-8L model.
You can always make extra and freeze the leftovers, but don’t leave them in the slow cooker to cool down for too long.
Searing slow cookers
Searing meat before slow cooking is important to allow caramelising and therefore more flavour to develop. There are models on the market that are able to sear meat and veggies, either in the slow cooker itself, or by transferring a removable inner pot to the cooktop. This removes the need for multiple pans (and extra washing up) when cooking meals that require searing.
Features to look for
Space : Consider how much food you anticipate cooking for you and your family, the cupboard space required for storage, and bench space for usage. Round slow cookers tend to waste space. Rectangular cookers generally use space more efficiently when in storage.
Indicator lights : Look for bright indicator lights and a control switch that’s easy to access and is clearly labelled.
Cracks and crevices : There should be few or no cracks or crevices for food to get trapped.
Cleaning : Each part should be easy to clean. A stainless steel exterior may show fingerprints and need more wiping. Large cooking bowls can be awkward to clean in the sink or fit in the dishwasher, and you need to be able to wash up!
Timer : A timer is handy as it counts down the time on your slow cooker and then alerts you when cooking is finished. Don’t confuse this with a delayed-start timer. A few members have been keen to get hold of a slow cooker with a delayed timer, which you can set to turn on or off while you’re away. We don’t reckon you should, as leaving food in the cooker at a warm-ish temperature will breed bacteria. If you find your slow cooker turns off prematurely, throw the food out straight away – it’s probably not worth risking food poisoning.
Automatic setting : This setting is handy as it starts the process on high to bring the food up to temperature and then switches to low temperature for the remaining cooking time.
For the elderly : Those with mobility issues should look for a cooker that’s not too big and is easy to handle – a huge bowl may be heavy or not fit into a small sink. It should have clear instructions and large, well-labelled controls at the front that are easy to operate.
Cost : Slow cookers usually cost anywhere from $20 to $250, but can cost more, depending on brand and features.
How to use a slow cooker
Make friends with your slow cooker to reap the rewards in the cooler months.
- Ingredients used in slow cookers are inexpensive. Buying cheaper cuts of meat that require longer cooking times will give better flavour and a tender result.
- Dried legumes, beans and pulses are perfect for the slow cooker and are cheap to buy. Boil dry beans for at least 10 minutes beforehand to destroy toxins that will otherwise survive the lower temperatures of a slow cooker (or soak overnight, then drain and rinse before using).
- Most ingredients can be prepared the night before, reducing prep time in the morning.
- For better flavour development, sear meats and cook off any spices before slow cooking. Some models of slow cookers let you sear in the slow cooker bowl, and some have a bowl that can be placed directly on a stovetop. This means you won’t need to use a frypan as well, cutting down on washing up.
- Food cut into similar-sized chunks will cook more evenly. It’s best to cut fast-cooking vegetables in larger pieces and add halfway through the cooking time.
- Condensation can build up under the lid which can increase the amount of liquid in the slow cooker and produce a watery sauce and weaker flavour. Add less liquid than required initially. You can always thicken it at the end of cooking.
- All food should be completely thawed, and perishable food should be kept refrigerated before putting it into the slow cooker.
Food safety tips
- Throw away food if there’s a prolonged power failure while your meal is cooking, as it may be unsafe to eat.
- Don’t keep food in the slow cooker for too long once it’s cooked. It needs to be kept hotter than 60°C (or cooler than 5°C) to avoid harmful bacteria growth. .
- Don’t reheat leftovers in a slow cooker – use a microwave, cook-top, or oven instead.
- Remove strong odours and residue build-up on ceramic bowls with bicarb soda or vinegar diluted in water.
- If you’ve left the slow cooker bowl in the fridge overnight because you’ve pre-prepared ingredients, take it out of the fridge at least a half hour before turning on the machine, otherwise you may need to cook the meal for longer.
- The auto-cook setting speeds up the cooking process slightly. It uses the high setting initially for approximately 30 minutes then reduces to low setting for the remainder of the cooking time. This is useful if your slow cooker is at maximum capacity.
- Add dairy products, cooked pasta and rice, fish or seafood in the last half hour of cooking so they don’t overcook. Avoid checking on the meal once it’s started cooking. You’ll only extend the cooking time if you lift the lid and let the moisture and heat escape.
- To convert a traditional recipe for a slow cooker, reduce the amount of liquid by half and increase the cooking time. One hour in the oven is equal to about six to eight hours on low in a slow cooker.
- Slow cookers can also be used for steamed puddings and baked custard. By adding water to the slow cooker bowl, the appliance can be used as a steamer, bain marie or water bath.
- A slow cooker can also be used to make fondues, preserves, chutneys and stocks.
- Food can be left unattended to bubble away in the slow cooker for approximately 8 hours if on the low setting. There are slow cookers on the market that have timers which can switch the machine to ‘keep warm’ at a set time.
- When cooking on high, keep an eye out for spillage. Condensation forms when the food heats up and, because all the lids are loose-fitting, it can splash out. So put your slow cooker where a few spills won’t matter, or keep an eye on it when cooking on high.
- Increasing the temperature to high at the end of cooking and removing the lid can be useful if the dish requires a reduction in the liquid, thickening with cornflour or you’re adding some leafy green vegetables.
Recipes intended for other cooking methods must be modified for slow cookers. Quantities of liquids may need adjustment, 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, and often use prepared sauces or seasonings. The long, moist cooking is particularly suitable for tough and cheap cuts of meat including pork shoulder, beef chuck and brisket. 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.