Hot Cupboards, Water Boilers And Water Heaters in Kitchen

One of the first rules of good cooking is to serve food at the temperature appropriate to the type of dish. It is as important to bring food to the table at the right temperature as it is to cook it properly. Many a good dish is ruined by being served too hot or too cold, although the fault is usually in the direction of having all food tepid. This is evidently not a fault of recent generations only, since in Revelations, Chapter III, the Laodiceans were rebuked and told by the angel that because they were lukewarm and neither hot nor cold he would spew them out of his mouth.

The problem of ensuring that cooked food reaches the table hot is a serious one even when only small numbers are being served, but in the kitchen producing hot meals for several hundreds of people it becomes more complicated and needs careful consideration of ways and means. Cooked food which is to be served hot should be sent to the table immediately the cooking process is completed, when it will be at the correct temperature for consumption. This ensures that there are no losses of aroma, flavor or nutritive value such as take place in the majority of foods when they are kept hot for any length of time, nor is there any deterioration in appearance and texture. This is important for most types of food, but is particularly so for vegetables which lose much of their nutritional value if they are kept hot for a period.

In large kitchens some delays are inevitable, owing to the distance the food must travel between kitchen and dining room and the difficulties of kitchen organisation. In a kitchen providing meals for the cafeteria system of service one can scarcely hope to achieve the ideal; such kitchens frequently cater for a service extending over a period of up to 2 hours, and even if relay cooking is practiced it is not possible to produce freshly cooked vegetables more frequently than, say, every half hour. Some arrangements must therefore be made to prevent heat losses during the serving period, and the provision of a hot cupboard is the usual method adopted.

In addition to ensuring that the food is hot at the time of serving, we must also see that the serving dishes and the plates are also hot. A cold plate or dish can quickly chill the food put on it, and in large dining rooms, where the distance from the servery to the table unavoidably causes heat losses in the food, it is even more important that plates should be adequately heated.

The uses therefore of a hot cupboard are the heating of plates and dishes and the prevention of heat losses in cooked foods which must stand about. For both of these uses the correct temperature of the air in the cupboard is important. Too high a temperature may damage the glaze of the china and even cause cracking, while even at low temperatures drying of uncovered food will inevitably occur, such drying being aggravated as the temperature rises. From 170°F. to 190 F. is the usual range, though lower temperatures can of course be obtained by reducing the supply of heat.

The hot cupboard is similar in design to the oven in that it consists of a metal box, with shelves, into which a source of heat is introduced, but whereas in the oven the heat is usually applied at the bottom, in the hot cupboard it may be applied also to the shelves and to the metal top. But the two are fundamentally similar, and an oven may of course be used in place of a hot cupboard provided it can be operated at a sufficiently low temperature. The essential difference between the two is one of temperature, and this in turn affects design; the hot cupboard is less robust and it is not usually provided with lagging. The high temperature in the oven makes thermal insulation of the walls essential in order to prevent unnecessary heat losses: the loss from the hot cupboard, run at a lower temperature is so much less that saving which would result from the provision of double walls with insulating material between is not usually considered sufficient to justify the additional cost in construction. There is, however, another point of view to be considered. The heat radiated from the surfaces of the hot cupboard will raise the kitchen temperature and add to the problem of temperature control, while the atmosphere immediately surrounding the hot cupboard will be hotter than it need be and will result in some discomfort to servers operating nearby. There may well be an argument for using hot cupboards with thermally insulated walls, and some manufacturers will supply them when specially required.

The most common sources of heat for hot cupboards are gas and electricity, the jets for the former and elements for the latter being similar to those supplied for ovens, but of lower thermal capacity in comparison with the cubic capacity of the equipment. Hot cupboards heated by solid fuel are obtainable but are not very practicable owing to the labor and dirt entailed in the fueling process. Hot cupboards heated by steam are also available. The steam is not used direct as live steam within the oven itself, but in a coil of pipes fixed to a plate in the base. Coils having an internal diameter of Z” and varying in length from 90ft. for a 4 hot cupboard to 240ft. for an 8′ cupboard are heated by steam at 151b. pressure. This method is very satisfactory because the temperature of the heating coils, 250°F., is much less than that of the gas jet or electrical element and consequently causes less drying of the air within the cupboard and consequent deterioration of the food.

Hot cupboards are usually constructed in mild steel with a Cast iron frame and legs, the external surface usually being protected with porcelain enamel for appearance and easy cleaning. The material used for the top is generally steel, either polished, chromium plated or stainless. Since this surface is used either as a serving counter or as a hot table on which dishes stand before service, it is liable to have food spilt on it and must therefore be made of material which is both easily cleaned and rust resisting.

The most common design for a hot cupboard is in the form of a table, usually 2′ q’ to 3′ in height, 2 to 2’6″ in depth and of widths varying from 2′ to ‘. Another type, also quite common, is the cabinet hot cupboard which is usually constructed in 2 tiers of total height 5′ 6″ to o as illustrated in Plate X. This form of hot cupboard is very convenient because it provides a large amount of accommodation for the minimum of floor space occupied, but it cannot of course be used as a serving counter. Widths and depths of cabinet hot cupboards are usually similar to those of the table type models, but for special cases where only a narrow space in the servery is available, Cabinet hot cupboards of l’ 2″ in depth are obtainable and prove useful.

While in the majority of cases these standard designs for hot cupboards meet all the requirements, there are special features which are frequently embodied to meet particular demands. Some of these modifications apply specially to fixed cupboards and some are introduced to provide portability. One of the most general and useful of these special features is the bain-marie which is a flat vessel to hold hot water in which other vessels are placed to keep the food in them hot. There are two types, the open and the closed. The former consists of a shallow rectangular pan usually fitted with a removable perforated submerged rack to keep the pans of the bottom and to allow the hot water to circulate around them. Containers of various shapes and sizes can be placed in this rack and the contents kept hot. The closed type is very similar but has in addition a cover with holes of suitable size and shape to accommodate various boxes and pots specially provided for this purpose. A great advantage of this model is that the escape of steam into the kitchen from the surface of the water is minimized. Another feature which may be incorporated in the enclosed type is the carving well with cover.

This is very useful for service counters where roast joints are kept during the serving period and carved as required. The cover may be detachable or of the roll type which swings out of the way to permit carving.

In the standard hot cupboard sliding doors are provided on one side only. Occasionally, however, particularly when the cupboard is placed between the kitchen and the servery it is useful to have doors on both sides sea that food can be put in on one side and taken out on the other, and models of this type are available.

In some new kitchen layouts where the wall between the kitchen and the server consists of push through storage cupboards either for hot or cold fund, the design of the hot cupboard has advanced still in the further Plate XXX can be seen the doors of large compartments into which can be pushed racks of cold food assembled in the kitchen. The small compartments with glass windows are for single contacts of hot food. In these, the food retains heat better than in a multi-compartment cupboard because On opening the door only a small area is cooled.

Another new development in many cafeterias is the move away from the fixed heated hot cupboard in the servery, to mobile individual items such as the heated lowerator for plates shown in Plate XXXI. This piece of equipment has the added advantage that it can be loaded in the dish washing room and without further handling the plates are ready for service.

Almost equally important with transported meals is the keeping of cold food cool and for which refrigeration temperatures of around 40°F. are required. Ingenious methods have been devised to provide for this in a mobile trolley which also keeps food hot. These trolleys, known as Meals on Wheels or Hot and Cold Carts, are made up of two separate compartments, one of which can be maintained at 180°F. and the other at 40°F. In one system a slotted tray is used which slides into the cart so that one portion of the tray is on the cold side and the other on the hot side. In another system two trays are used a small one for the hot food and a larger one for the cold food and on to which the hot food is transferred before the tray is taken to the patient. To facilitate the transfer of the food, a rack is provided on the door for the tray for use while the hot food is being put on it. The thermal performance of this trolley is claimed to be 11 minutes for preheating from 70°F to 180°F and for pre-cooling from 70°F. to 40°F.

Another method of keeping transported food hot already described in Chapter 5 is by means of a preheated aluminium alloy pellet enclosed in a stainless steel container.

In certain circumstances where cooked food is consumed at some considerable distance from the kitchen, as in hospital wards and dining rooms remote from the kitchens supplying them, it is necessary to have means of keeping the food hot during transit. For this purpose the hot cupboard is made transportable by the provision of wheels and heated electrically, this being the only form of heating suitable under these conditions. The cupboard must be plugged in and heated up in the kitchen before loading and again in the ward kitchen or dining room servery after transit. These hot food service trolleys, or hot locks’ as they are often called, are made in various sizes and types to suit requirements. When size is being considered, however, the total weight of the fully loaded trolley must be borne in mind. It is found that the biggest convenient size is about 3′ x 2′ x 3′; a trolley of this size can when fully loaded be pushed without too much effort.