The following information is provided courtesy of The Catering Equipment Suppliers Association.

Warming cold food such as pies or sausage rolls or keeping food which has been freshly cooked at serving temperature needs careful food safety handling and the right equipment. It is not just about maintaining the heat to help keep the food safe to eat, but to keep it in a fresh condition.  

Dry heat will keep food warm, but if the food is susceptible to drying out, then dry heat will over a period of time fail to deliver food items in the best condition. Foods with have a high moisture content such as pasta dishes, or a high fat content such as pies and sausage rolls, will keep well in dry heat cabinets. Food items such as cooked chicken will hold over a short period of time in a dry heat display cabinet, but are better stored in a cabinet that has a humidifier that injects a small amount of moisture in the cabinet to prevent drying out, but not induce sogginess. 

Food can also be held hot in serving dishes using underneath heating units or in the traditional chafing dishes which use spirit lamps for heat. These are some of the ways in which food can be held hot. 

Snack warmer cabinets 

These are not just warming cabinets, but merchandisers, so the food being held must appear attractive in order to assist sales. Apart from an attractive cabinet with good all-round vision, lighting in the cabinet will add to the appeal of the food. If the cabinet is fitted with a humidifier, the foods in the cabinet will stay fresher and moist for a much longer period than in a dry-heat only cabinet.  

Humidifiers can be something as simple as a built-in water trough which causes water vapour to be released into the cabinet. The more sophisticated models will have atmospheric as well as temperature automatic control. Check to see if there is a feature on the unit which prevents misting up, preventing the food from being properly viewed. Doors on two sides can be useful in self-service situations, with food being loaded from the back and the customer taking from the front. 

Chafing dishes 

These the traditional way of serving hot food at a self-service buffet. They should be gastronorm compatible to allow for a full tray of food to be inserted over the water bath. A spirit lamp underneath the unit keeps the water hot, but it is possible to get electrically heated chafing dishes. These are potentially safer, but there is less mobility with the need for a power socket. 

Cheap chafing dishes will have lift-off lids, which are awkward for the customer. Better units will have a roll-over lid allowing the customer to hold a plate with one hand and a serving spoon with the other.  

Electric heat pads 

These are flat pads with an electric heating element inside. The base should be insulated to prevent undue heat loss, but it may still be necessary to place a protective mat underneath if the pad is sited on wood. The advantage of them is that food that has been prepared in an oven dish such as fish pie that cannot easily be transferred into a chafing dish can be on the menu. 

While standard electric heating elements are the norm, it is now possible to get heat pads which work using induction heating. While the heat can be set high for theatre cooking in front of the customer, some have a hold-only mode which just emits a gentle heat. 

Hot cupboards 

Traditionally, these would be fixed units in the kitchen into which plated hot meals would be placed in stacks separated by a plate ring with a top cover on top to help prevent drying out. 
While fixed hot cupboards are still widely available, they are much more versatile if they are on castors with a brake mechanism. The shelving arrangement can be flexible, with many shelves to take single plates or to use the stacking system. Gastronorm size compatibility is useful for keeping batches of food warm. 

The top can be a solid work surface or have dry or wet heated bains marie so that things such as saucing, gravy or custard can be added at the point of delivery to prevent skinning. 

Ease of cleaning is very important, as food debris not wiped up is a serious food hygiene risk. There is often a range of accessories for hot cupboards, including tray slides, sneeze screens and digital temperature display.