Depositing is a form of extrusion which allows for the formation of dough pieces that are soft such that they are pourable. During depositing, the dough is forced through orifices that have been pressurized either by means of a pump for sponge batters or rollers for soft and short dough. Depositing is one of the simplest ways of making dough pieces.
Depositing technique involves the forcing of pourable dough through holes in a die plate. Depositing machines are relatively simple in design. The batter pressure inside the pressure chamber behind the dies is achieved and thereafter maintained by the friction of the batter that occurs while on the feed rollers. Such frictional force will be altered should the consistency of the batter with regards to softness and stickiness also change. When the speed of the feed rollers is altered, it is possible to generally control the rate of depositing and subsequently the weight of the piece of dough. This will in turn result in a pressure reduction or increase of the batter that is inside the chamber beneath.
Drag forces continue to act on the batter from the sides of the depositing machine. Typically, the pressure across the pressure chamber will not be uniform and more batter needs to be deposited from the dies at the machine centre, rather than from those at the sides. Compensating for this would be very difficult by simply making the dies to be of a different aperture. Therefore adjustable restrictors are commonly provided as they allow the operator to effect some control over the depositing rate and in turn the weight of the dough piece. The restrictors will consist typically of plugs that can be screwed into the sides of the die hole, and when they are screwed in the result in the ultimate reduction of the size of the die.
Balancing the weight of the dough piece across the oven band is a task that is often frustrating and complicated. When the depositing machine is started, pressure will build up in the chamber until it reaches a steady state. And as the depositing machine is stopped, this pressure will fall slowly due to the continuous depositing that is taking place through the dies. As such, the adjustment effects on the die restrictors can only be checked once the machine has been left to run for a couple of minutes. It is not usually safe or even possible to adjust the restrictors while the depositing machine runs. Moreover, if the dough consistency varies, either within a batch because of the age of the dough, or between different batches, the variation in depositing from the dies may be impacted as well.
The size of the batter that is deposited can be controlled simply by the length of time that the dies are left open. Often, there will be a variation of the weight of the batter deposits across the oven band. However, this is generally regarded as being less of a problem for the depositing machines. An ideal unit would have divider plates relating to every die hole or at the minimum to every pair of die holes.
Where the dough is of a smooth, soft and almost pourable consistency, it is possible to produce deposited dough pieces rather than those that require wire cutting. The batter plate is replaced with a set of piping nozzles which are cone shaped and may have ends that are patterned so as to provide strong relief to the dough that is deposited. Individual deposits may be achieved through the lowering and raising of the oven band such that it coincides with intermittent depositing. This is achieved through the intermittent movement behind the nozzles of the feed rolls. When the band is raised to be near the nozzles, batter is then forced out and it spreads onto the oven band.
At the end of the depositing, the oven band is allowed to fall back and the deposit can then break away from the nozzle. The breakaway may be encouraged through a reversing action of the feed rollers. This will stop the feeding to the nozzles or may produce a suck back. It should be noted that through the utilization of variable mechanisms and times which twist the nozzles, it is possible to produce circles, swirls, fingers and other dough piece shapes. Furthermore, the synchronization of a second depositor with the first one allows for the depositing of jelly or jam, as well as another dough on or inside the deposit that was made by the first one.
There are various types of cookies and biscuits that are manufactured out of foamed egg batter. Deposits of this type of batter will typically be made directly onto the oven band from a pipe that is positioned over the band. The batter will then be pumped through the pipe and thereafter deposited through small die holes that are closed and opened at intervals.
Depositing machines create a variety of structural biscuit or cookie shapes that may then be deposited. This is offers a flexible alternative to the conventional dough forming and sheeting systems, as well as new cost effective opportunities for the snack food industry. Depositing machines allow for the accurate and consistent production of products from hard biscuit sticks and shapes to chocolate chip cookies. For product changeover, simply exchange one head and die for another one that has a different shape. Most units have a simple assembly that allows for product changeover within minutes.
Depositing machines allow for the high speed production of complex shapes by forcing batter through dies that have been mounted onto the end of the machine. Such dies are interchangeable and allow the operator to create various differently sized and shaped products on a single production line. Dies can be custom designed such that they are able to make almost any product of any shape.
Potential Problems and Solutions