When boiling, baking, frying, roasting, stewing and steaming can be performed by a single cooker, would that be your “one-for-all” weapon in kitchen? A multi-cooker makes your dream come true! The multi-cooker, often seen in Asian and European kitchens, has significantly improved the quality and efficiency of cooking. As an advanced combination of the slow cooker and the pressure cooker, the multi-cooker became more and more popular in modern kitchens. This article describes how a multi-cooker works and explains the details of the internal control system. A multi-cooker controls the temperature and pressure inside the cooker by manipulate the heat flow rate and amount of steam in the cooker in order to properly cook the food. The most fascinating thing about multi-cooker is that it has multiple embedded functions that can be applied to different types of food by simply clicking on these functional bottoms.
Allow commercial talks about how good it is:
Pressure and temperature of multi-cooker are controlled variables that are significant in this control process. Depending on the property of food (i.e. texture, liquid content and solid content) and the cooking style, setpoints of temperature and pressure under which condition the food can be properly cooked will be experimentally determined. A multi-cooker usually uses a negative feedback loop where temperature and pressure of the cooker can be adjusted to reach setpoints. Typically, the temperature and pressure sensors measure the temperature and pressure in the cooker, and compare measured values with the set points. Then a controller will make decision and take action to adjust the temperature and pressure to approach their setpoints. In order to speed up cooking process, maintain the original flavors of food, it’s important to keep the cooker pressure and temperature in a reasonable range or at a specific value to ensure the cooker working at a relatively high efficiency and avoid potential safety issues.
In order to minimize the difference between cooker temperature and the set point, it’s necessary to adjust the other term called manipulated variables, which are controlled by the controller mentioned above. In the multicooker, the manipulated variables are temperature and pressure of the cooker.
To control the temperature of the cooker, heat flow rate is one of the main manipulated variables which varies in order to minimize the difference between cooker temperature and the set point. As mentioned, the manipulation of heat flow rate by the cooker itself can be achieved by a feedback response provided from a temperature sensor in the cooker. For instance, the best temperature of cooking steak is about 140 degree Fahrenheit, the moisture inside the steak was heated from room temperature to a higher temperature. At the beginning, the heat flow rate transferred in by a thermal panel will be much higher compared to middle or final stage of cooking. Later in the process, the temperature of steak will not be higher than the set point (140 degree Fahrenheit) ideally. Such adjustment can be done by a controller, which in this case, would be a thermal converter that converts electricity to heat. Specifically, An adjustable resistor in a circuit board then manipulates the heat flow rate in order to change the temperature of cooker.
On the other hand, the manipulated variable for the pressure in a cooker is the amount of steam. The pressure of the cooker usually reaches as high as 2 bars. Making the boiling point of liquid (usually water, sometimes wine or broth) in the pot higher than its normal boiling point at atmospheric pressure. A rise of pressure lets the food inside the pot to be cooked at a higher temperature thus the time needed for cooking has shorten by a large amount. This characteristic function is borrowed from pressure cooker where the food will not be smashed because the pressure formed by steam that applies pressure uniformly across the entire cooker. As long as there is some amount of liquid in the cooker, steam can be generated by the heat provided. In order to control this process, a fail-close (ATO) valve works as a controller to automatically adjust the amount of steam in the pot in order to control the cooker pressure. For example, when the pressure inside the cooker is too high compare to its setpoint value, the sensor then will let the valve to be open in order to release some steam.
However, there are some other factors, known as disturbance variables, which may disturb the control system. Disturbance variables have effects on the controlled variables but they cannot be manipulated in the process. In the multi-cooker, the potential disturbances are heat or gas leak from the cooker and disruption of electric current.
Ideally, the current supplied to a multi-cooker is stable and constant. As a result, the cooker can have a stable rate to transfer electrical energy into heat in order to allow its internal system to calculate how much time is needed to achieve the set point. In this case, any changes or disruption on the electric current can negatively affect the efficiency of the cooker and disturb the system. For example, if the amount of electric energy supplied into the cooker is less than the steady state value, it will make multi-cooker to take longer to achieve the desired temperature and pressure. The heat or steam leak from the cooker is also unpredictable and hard to control. Usually designers will try to avoid the leaks, but the possibility of leaks is still present when a cooker has been worked for a long time and some components failed to function properly. Other disturbances include the adjustment on the desired temperature or pressure, known as controlled disturbance. As we change the set points, the time for heating or pressurizing will be changed accordingly. It’s recommended to determine the desired temperature and pressure, which are corresponding to different programs embedded in the multi-cooker before the it starts to work to avoid the controlled disturbance.
Furthermore, the time which takes the cooker to adjust temperature from initial values to setpoints, there is a further time period needed for cook food thoroughly. Such period is set as well as a timer that allows people to see how long it takes for the food to be ready. The length of this period depends on the category of food just like how the temperature and pressure set by experiments. During this period, the cooker will theoretically keep running at the same temperature and pressure. However, the temperature and pressure might be unstable thus same controllers will be working in order to cover the difference.
As an independent household appliance, a multi-cooker saves your money, time and space compared to old styles cooking equipment: all kinds of pans, steamer, slow cooker and oven. Multi-cooker, a universal solution which can replace all of the above appliances, it can even be a fryer when you leave the lid open. Especially, when compared to a slow cooker which cooks food slowly and at low temperatures, it mainly takes you several hours to cook meat in the slow cooker that is an unimaginable luxury for a modern person! The Multi Cooker, in the contrary, cooks twice as fast than a stove. It concerns even the most complicated dishes which require long thermal processing. Also the slow cooker is not recommended for food reheating while it is quick and easy to do so by a multi-cooker.
The feedback-loop multi-cooker owns, enhances its advantage even more, compared to a pressure cooker which can only adjusted by turning on/off stove, has a more advanced adjusting system as a more automatic appliance since temperature and pressure are controlled. Manipulated variables like heat flow rate and amount of steam altered by controllers (resistor and valve), also help the cooker for making delicious cuisine. If there is anything else that can be improvement based on the current model, safety should be considered. A pressure release valve might be involved when electric current suddenly drops to prevent a rapid decrease in pressure. But overall, multi-cooker will be a powerful tool in your kitchen.