Baking biscuits is the process of biscuit or cookie production in which the products are baked inside a tunnel oven in a continuous process in heated and controlled zones. During this stage of the biscuit or cookie making process, moulded dough pieces are placed into the baking oven and cooked at set temperatures.
Most cookies and biscuits are baked in a tunnel oven in a continuous process. Trays of dough pieces are placed into the oven and removed after a suitable interval. Biscuits and cookies are typically baked inside long tunnel ovens made of several independently heated and controlled zones. The shortest ovens may have a single zone, but the longer ones may have two or more zones. The most common configuration is 3-4 zones. The availability of multiple zones allows for the provision of varying temperatures, extraction conditions and heat applications as the pieces of dough are baked into cookies and biscuits.
The products undergo various heating methods such as convection, conduction and radiation which facilitate the baking process. The ovens will also have dampers which are designed to control the moisture content inside the oven section. While inside the oven, the biscuits and cookies are transported on a metal wire mesh or a sheet of steel.
Baking times for cookies and biscuits are rather short, ranging from 2.5 to 15 minutes. Normally, it is not possible to quickly change the temperature of a reel or static oven. Therefore the results of baking in such ovens are often quite different in comparison to baking in traveling ovens. The required conditions for different cookie and biscuit types will not be the same. This is because the manner in which the structure has been developed, and the moisture amount that must be removed is dependent on the richness of the recipe. The richness refers to the level of sugar and fat ingredients used during the mixing process.
Four major changes can be noted in the biscuits or cookies as they are baked. First, there is a large reduction in the density of the product that is associated with the development of a flaky or open porous structure. During this time, the dough will typically get thicker. The second change is with regards to the shape of the product that is associated with spread or shrinkage, along with an increase in overall thickness. A reduction of the level of moisture to between 1-4% is another key change that occurs during baking. Finally, you will also notice a reflectance, which is a change in the coloration for the surface of the cookie or biscuit.
The oven’s production rate is defined by its length, as well as the baking time required to bake the product to the desired color, structure and moisture content. Biscuit ovens are designed to dissipate heat either directly or indirectly into the chamber of the oven. Extraction of the atmosphere of the oven is through ducts and flue pipes that remove the gases out through the factory roof. Extraction may be done naturally or assisted by fans. The latter is preferred because natural extraction tends to be affected greatly by speeds of wind and temperatures outside the building. The amount of extraction is controlled by a slide valve contained in the flue pipe, typically before the extraction fan.
Ovens have numerous control points that offer a wide range of possibilities. The cookies or biscuits are taken through the oven on a continuous band. While moving through the oven, the band is supported on rollers or metal skids that are spaced closely enough to prevent sagging of the band in between them. After passing through the oven, the band will return under the oven, typically outside the hot chamber. In such a position, it may then be cleaned by the fabric or wire rotating brushes. In certain cases, provision is made for the treatment of the band or its surface immediately before panning the pieces of dough onto it. Items used here include oil sprays, rollers, flour dusters and pre-heaters.
Many of the modern oven structures are light weight and insulated with fiberglass and rock wool. Turbulence is utilized for the enhancement of heat exchange, which introduces the need to achieve uniform and controllable movement of air within the oven. Provisions are made for varying the heat ratio that is supplied to the top and bottom of the cookies and biscuits.
Biscuit/ Cookie Baking Oven
The baking ovens for biscuits and cookies comprise of a steel steam tight tunnel with radiator zones that are equally divided. There are stainless steel expansion joints between the zones for purposes of eliminating the expansion of the oven section. There are inspection doors provided which allow for the inspection of the baking products during the baking process.
The complete chamber of the biscuit making oven will be insulated from the outside, thereby conserving heat and increasing efficiency. The imported burner is fully automatic and can be fitted to the chamber. The temperature is then controlled via an automatic temperature controller on the control panel. The complete oven is covered with a mineral wool insulation that is 10” thick, on the sides and from top to bottom. The bottom section of the oven at the sides is covered by sheets that offer protection to the conveyor, while also preventing heat loss.
The baking inside the heat chamber of the baking oven occurs through radiators that are located above and under the wire mesh which distributes heat, thereby allowing for uniform baking. It is possible to control the recirculation of heating gases separately for each individual zone. The closed recirculation system has a slightly vacuum atmosphere such that combustion gases are not able to enter into the baking chamber. The ventilating fan is designed to allow for the circulation of the heating gases through the recirculation system. During this process, the burners that are thermostatically controlled provide the set temperature of the heating gases. All the circulating fans are well balanced to avoid vibration and will provide noise free operation at high speeds.
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