In considering the equipment for baking and roasting we observe that there is much in common in the requirements for the two processes. Both require an oven which is usually of metal construction, but in special cases may be of brick. The heat may be obtained either externally by a fire or by the hot gases from a fire passing through flues, or internally by gas burners, electric elements or steam pipes working at high pressure.
Both roasting and baking call for careful temperature distribution in the oven and convenient automatic or manual control to ensure suitable temperatures for the various products. The only essential difference lies in the shape and dimensions most convenient for carrying out the two processes, and this difference assumes greater importance in connection with special work such as that carried out in bakers’ ovens. The baker requires a large oven maintained at one temperature so that there is uniformity of appearance among the many items baked. For different products bread, tarts, buns, etc.–the requires different temperatures, but in all cases the temperature must be the same throughout the whole process. These conditions are best secured by having shallow oven with the minimum clearance between floor and top.
New considerations arise when an oven is required for general purposes and is not restricted to baking large numbers of articles only. There may be wide variations in the size of the articles to be cooked, the number wanted at any one time, and the temperature requirements of the various items and consequently a temperature variation over different parts of the oven may be a decided advantage. The ease with which certain articles can be taken out or replaced leaving others undisturbed, is also an important factor. These requirements are best met by increasing the height in relation to the floor area and inserting additional racks. This gives both temperature range and accessibility. An added advantage of this more compact oven lies in the space requirements in the kitchen layout. Whereas the baker’s oven requires a floor area of considerable size, the general purpose oven by making use of greater height can be fitted into a much smaller floor space.
The oven requirements are somewhat different for a food service unit such as those in the school meals service, where the output of a large number of the same dish, such as say hot-pot or fruit pie, are required. For this an oven similar to a general purpose model is required but one having all shelves at the same temperature, rather than a range of temperature from top to bottom. Such an oven now available in the Lasmec range of equipment is described below.
Design for Convenience
Convenience in use which is one of the first considerations in estimating the merits of an oven, depends on a number of factors. The distance from front to back must be such that it is possible for the cook to reach easily those dishes which are placed at the back of the oven, although this does not apply in the case of a baker’s oven where a long wooden pole with a fiat disc on one end, known as a peeler, is used to insert and remove articles.
Again, the design of the doors must be such as to allow of easy access. A drop door with a handle at the top and hinges along the lower edge may cause burns if it is of such dimensions that it is not possible for the cook to reach into the oven without touching the door in its dropped position. Burns may also result if oven doors with side hinges are so fixed that they cannot swing through more than 90° and so impede freedom of manipulation on one side.
The height of an oven from the ground is yet another factor which contributes to ease in use. The most convenient height for the manipulation of tins in an oven is at waist level. Oven shelves placed not more than 2′ above or below this height are reasonably convenient to operate, but if fixed at a lower level entail unnecessary bending and extra lifting. If the shelves are placed at a higher level it may be necessary for the operator to use a stool in loading and unloading and this, in addition to making the work heavier, may be dangerous when dishes with hot liquids, particularly fats, are being handled. Thus it appears that the most convenient height for oven shelves is between 2′ and s’ although of course the range of height must vary according to the heights of the operators.
Still another important consideration is the design of the fittings for the oven shelves. These fittings should enable shelves to be inserted and withdrawn easily, and this is particularly important since this operation must frequently be carried out while the oven is hot.
Among the various factors to be considered under the general heading of efficiency are some such as the detailed design and placing of the burners which are too technical to be dealt with here. Others, however, are of direct concern to the cook and deserve due consideration. The first requirement of an oven in this respect is that it should cook evenly. This is of course to a great extent dependent on the design of the oven as settled by the manufacturer. Naturally it is reasonable for the user to expect an even temperature distribution over each shelf. The extent to which the performance of a particular oven complies with this requirement can only be determined in use. Where there is found to be an uneven temperature distribution the matter should be taken up with the manufacturers.
The next point to consider is oven insulation. Owing to the high temperature inside the oven it is clear that considerable loss of heat would take place unless some form of lagging were adopted.
The usual construction is to have a double shell, the inner one being the oven proper and the outer one affording protection and riving a good external appearance. The space between the two is usually filled with one of a number of heat insulating materials such as slag wool or glass fiber; this must also be heat resisting so is not to deteriorate with time. Such lagging ensures not only that fuel is used to the best advantage but also that the increase in the temperature of the kitchen by heat losses is reduced to a minimum. As has already been pointed out in Chapter 2, defects in oven lagging can give rise to serious problems of temperature control in kitchens.
The ease with which an oven can be cleaned and the way in which the materials of which it is constructed stand up to working conditions are of great importance in assessing the merits of such equipment. High temperatures and the nature of the materials causing soiling combine to make the problem of cleaning a serious one. It is therefore essential that the inner surfaces should be smooth, hard and non-porous and moreover that they should not deteriorate when constantly subjected to high temperatures. One material in most common use for this purpose today is vitreous enamel, which fulfills well the conditions enumerated above. Faults in manufacture however sometimes occur leading to chipping and cracking, but these are comparatively rare and should be reported to the manufacturer so that the damaged parts can be replaced. Another material now used fairly commonly and found to be very satisfactory is stainless steel. Nor is the actual surface of the oven the only part requiring careful cleaning. The shelves and their fittings and the gas burners will all have to be cleaned frequently and should be so made to facilitate this work.