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How to bake cookies and crackers

When it comes to ovens, it’s not one size fits all. Tunnel ovens, popular in the 20th century,  were little more than insulated and heated cabinets through which a conveyor passed. Band ovens used today are far more sophisticated than the original ovens, however the classic definition of a tunnel, or band oven, remains as valid today as it did then.

 


Cookie types

Cookies, or biscuits are available in an endless number of variations, but four major forming methods account for most of the varieties.

Wirecut Cookie

Probably the first type of biscuit made, it originally consisted of a mixture of flour, sugar or honey, butter and milk. A soft and pliable dough was formed and spooned out of the mixing bowl, spoon by spoon, onto the baking pan. The modern wirecut machine consists mainly of a hopper for the dough and two rolls which rotate towards each other, forcing the dough downwards. A pair of scrapers peels the dough from the rolls and help force it downwards and into a cavity located beneath the rolls.

Cutting Machine Cookies

The second type of biscuit, cutting machine biscuits were made by rolling a piece of dough into a sheet, cutting various shaped pieces from it, and baking them. They are no longer cut by hand, nowadays cutting, stamping and dyeing are done mechanically.

Rotary Molded Cookies:

Cream filled sandwiches required flat, thin and uniform cookies and the base cake for these sandwiches was originally produced on stamping lines since they had the special product characteristics required. Setting up and operating a stamping line is costly and, on this basis, another way of forming these cookies was needed. The rotary molding machine was introduced in 1904 and the modern version consists of a hopper and, at its base, two rolls which rotate towards each other.

Deposit Cookies

The final major category of cookies is the deposit, or "spritz" type. These are normally made from a soft,high shortening dough, and are squeezed from tubes directly onto the baking band. While a separate deposit machine may be used for this type of production, a wirecut machine with a depositor feature ("wirecut/ depositor") is also available

Baking bands and baking meshes

The conveyor belt of a band oven can be either a metal baking mesh or a solid steel baking band. But, within these two major types of baking belts, a wide number of options are available to meet the needs of the specific product or the special desires of the baker.

Baking Meshes

The diameter of the wire, its shape, and the pattern of the weave can be varied over a wide range. The result is that the baking mesh can be as thin and light as a piece of window screening; as open as chicken wire fencing; or as solid, heavy, and nearly airtight as the heavy cordweave meshes used extensively in cracker baking.

Baking Bands

Baking bands are fabricated from tempered carbon steel and are blue-black in color. (Stainless steel has such poor heat transmitting characteristics that it is not used for cookie and cracker baking). As opposed to baking meshes which are normally measured in inches of width, solid steel baking bands are usually sold in metric widths. Solid steel bands can be supplied in various thicknesses, as well as various widths, and the most widely used types are between 1.0 and 1.4 mm thick.

Heated cabinet

The cabinet portion of a band oven consists of an inner case, insulation, and an outer case. The main function of the inner case, or baking chamber, is to provide an enclosure within which the product can be baked.

A good insulation is essential. A rule of thumb is the "hand test". In the "hand test" sufficient insulation has been used if it is possible to rest one's hand on the oven case without injury or discomfort. The cabinet of a well designed oven will have sufficient inspection doors so that the product can be visually inspected at various points along the length of the baking chamber. In addition, where topped products (such as salt covered saltines) are being baked, cleanout doors (usually located along the non-operating side) are strongly recommended so that the baking chamber can be easily and periodically cleaned.

The final two elements of the heated chamber section of a band oven are the exhaust system and the heating system.

Heat transfer and baking

Simple or complex, all ovens depend on three means of heat transfer which are:

Conductance

Conductance, or heat transfer of contact. Place a piece of cold dough on a heated piece of metal and the heat is transferred from the metal into the dough and the dough soon becomes hot.

Convection

Convection, or heat transfer of blowing heated air onto an object. The household hair dryer is a good example of how effective heat transfer by convection can be. Set the dryer on "high" and hold it close to the head and it soon becomes quite hot-an indication that a large amount of heat is being transferred quickly.

Radiation

Radiation heat transfer is defined as being the generation of energy by an emitter, the movement of energy in wave form through space without being changed, and this energy then changing to heat energy when it strikes a receiver.

An example of a quite common radiant heat generator is the bread toaster found in most kitchens. The glowing wires produce large quantities of radiant energy and, when this wave form energy strikes the slices of bread, it becomes heat energy and toasts the bread.

Baking objectives

What is baking? Baking can best be defined by the objectives to be achieved, and these are - 

Water Removal

The first objective is the removal of water, or moisture, from the dough. Cracker doughs contain about 30 percent total water. The objective of baking is reduce this to between one and two percent in the final product. About 28kg of water will be removed for every 100kg of dough. Heating this quantity of water to the boiling point, converting the boiling water to steam, and then heating the steam still more so that it does not condense as it is exhausted from the oven requires a great deal of energy.

Crust Coloring

The second objective of baking is the coloring of the product's crust. Consumer has been conditioned to expect some crust color on baked products, this color is important for more than simple visual gratification. A cookie could probably be produced fully baked, but looks pale and almost white. Its taste would tend to be bland and uninteresting by most standards, since the color of the crust is a very good indication of the quantity of surface sugars that have been caramelized. A colored crust indicates that some caramelization has occurred and that there is a bittersweet flavor present, and most people prefer and enjoy this flavor.

Cooking

The final objective of baking is a group of physical and chemical changes which can be lumped together under the definition of "cooking". The reason for using this term is that many of these changes take place more or less concurrently; many require the presence of moisture; most require time; and  many  of  these changes, while requiring heat, will take place only between  certain  temperature limits.

As an example of a physical change, before a loaf of bread enters the oven it is "proofed" and allowed to increase in volume. This expansion is a key factor in developing the open texture of the loaf. A cookie enters the oven almost as soon as it has been formed and is a fairly solid and dense lump of dough. However, most cookie doughs contain leavening materials which react when heated and generate gases which "open-up" the texture of the product. This development of the internal structure is one example of a physical change which can take place during the baking of a cookie.

Cookie baking

Cookies after they are baked, normally enter the oven as dense and fairly solid pieces and most containing various types and quantities of leavening agents and, as heat is applied, gases are generated. If, however, an excessive amount of  top  heat is applied too quickly, a crust will have been formed and it will physically limit the degree of "lift", or expansion  upwards, which can take place.

Biscuit doughs usually contain relatively high levels of syrups and sugars, and may also contain high levels of shortening. If only bottom heat is applied, or a majority of the heat comes from the bottom, the dough will become warm and the syrups become more fluid, the sugars may change to liquid, and the shortening will melt. As a result, the biscuit will increase in diameter, or spread. A compromise must be reached between baking the product with settings that will achieve maximum efficiency in water removal and in baking in such a way that other desired characteristics are developed.

Cracker baking

The removal of water is a major objective in cracker baking. The way in which this moisture is removed is also important, since the method can have a dramatic effect on the characteristics of the baked product.

Doughs used for snack crackers generally contain one or more types of leavening materials. The primary purpose of most of these leavening agents is not mainly for their potential as leavening agents, but in their ability to modify the characteristics of the dough in the "lay" period that precedes their delivery to the forming machines.

Once it reaches the forming machines the first requirement is to convert the mass of dough into a smooth, continuous, and thin sheet. This is achieved by passing the dough through a series of inline reduction rolls. Any gases that were developed during the "lay" time will have been almost fully expelled in the rolling process. An open texture is required in the product and can be achieved if sufficient heat can be transferred to the dough sheet quickly enough to change the water within the product to steam, and thus literally "open-up", or "explode" the dough. This rapid heat transfer is accomplished by using a very heavy cordweave steel baking mesh and preheating it. Since the mesh has a high degree of "mass", or weight, and it is made from metal, it can hold a large amount of heat. The heat necessary to rapidly convert a part of the cracker moisture to steam is readily available from this "heat-bank" and the crackers will be delivered with an open texture-thanks to water and the proper application of heat!

 

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