Cooking in a pot: direct or indirect heating?

 

The electric cooking pot is sometimes known as a “hot pot” or “electric multicooker”.

 

Principle

 

An electric cooking pot is an item of equipment similar to a saucepan that allows food to be cooked on a large scale by heating with oil or water.

 

It consists of a fixed or tilting deep cylindrical or rectangular tank and is used in large, busy kitchens to cook pasta, soups, etc.

 

Description

 

There are two cooking systems: direct heating and indirect heating.

 

Direct heating

Pots with a direct heating cooking system have a single tank. Shielded resistors or resistant wires are mounted on ceramic and placed at the tank’s base.

 

Indirect heating

With an indirect heating system or in a bain-marie, there is a double-walled tank.

There are four different systems:

 

1. Heating elements (immersion heaters) are located in the double jacket. The water supply must be provided manually. Limescale deposits can form over time due to water renewal.

 

2. This system is identical to the previous one, except that the double jacket contains oil in a sealed circuit. The latter eliminates the need to renew the fluid and allows a higher degree of heating (180°C).

 

3. The third version is powered by steam in a closed circuit. A separate generator produces the steam. The double jacket is put under low pressure. Everything is powered by electricity; water replenishment is rarely necessary and is automatic.

 

4. The fourth system is identical to the previous one, but the water used is anti-corrosive, and the double jacket is put under high pressure.

 

For systems with water or steam, the pot is equipped with a safety device that releases the steam from the double jacket when its pressure is higher than the normal pressure of use. In addition, there is a device that avoids the risk of deterioration for lack of water (106°C), a direct water supply and an evacuation system for cleaning.

 

Some pots are fixed, others tilting. The system can be manual tilting (worm wheel or lever) or assisted (hydraulic, electric or pneumatic). Tilting models facilitate emptying: the cooking water can flow out while the solid ingredients (vegetables, potatoes, rice, pasta, etc.) remain in the bowl. In addition, tilting pots are easier to wash after use.

 

Rectangular models offer the advantage that you can fit one or more gastronorms (rectangular food containers).

 

Many models of electric cook pots are now equipped with a stirrer, not to be confused with a soup blender. This accessory is helpful for numerous applications, including:

 

• Heating by integrating a slow or interrupted movement
• Mixing quickly
• Mixing in both directions
• Preparing mashed potatoes
• Preparing hot and cold desserts

 

In addition, stirrers allow a mixture to be cooled rapidly and within the required time, using either tap water or chilled water.

 

Some electric cooking pots have a temperature display that measures the ingredients inside the pot itself.

 

Other models have sealed lids for cooking under pressure at 110°C at 0.5 bar.

 

 

Controls

 

Controlling and programming are carried out by switch, energy regulator or thermostat.

 

Currently, programmers allow programming the most common and repetitive cooking processes. Even better, some very elaborate programmes transmit the automatic progress of the entire production cycle: filling, cooking, mixing, cooling. Moreover, you can start this programme at night, so when the chef arrives in the kitchen, most of the work has been done, and all that remains is to reheat. Furthermore, cooking temperatures and times can be recorded, which allows the traceability recommended by HACCP.

 

Some appliances also allow a cleaning programme for the pot and auxiliary parts.

 

Range

 

Capacity from 20 to 300 litres for commercial catering.

 

Average power for 10 litres (provide a capacity of 0.5 to 1 litre per portion prepared):

 

• direct heating 1 kW
• indirect heating 1.5 kW

Installation

 

Provide a cold and hot water supply; the latter reduces the heating time. Channels at least 20 cm deep covered with floor grids and connected to the wastewater network must be installed in front of the pots.

 

Applications

 

Many cooking methods previously carried out in electric pots are now carried out in forced convection ovens and combined air-steam ovens or steam cookers, limiting their use.

 

Indirectly heated stockpots are appreciated for cooking foods that risk sticking including dairy products, stir-fries, purees. They are also ideal for cooking pasta and using as a bain-marie.

 

For the same total capacity, it is recommended to install several devices to obtain more flexibility.

 

Energy efficiency

 

The bowl transfers heat to the food. Therefore, the contact surface must be as large as possible to obtain the best transfer and optimal performance. For this reason, narrow and deep or wide and flat pots are not recommended.