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Cooling and Handling in Biscuit Production

Before transferring freshly baked biscuits and cookies from the oven to the wrapping machines, it is important to ensure that the product is cool enough for handling. Cooling is similarly important for biscuits rich in sugar, as these tend to be very soft and plastic while leaving the oven, and are only able to set rigid once they have cooled down.

 


Baking experts feel that if biscuits and cookies are packed too hot, they will end up sweating in the pack. Cooling is therefore important in ensuring a significant loss of moisture in the product.

Process

After baking, most cookies and biscuits will go directly for packaging. This allows them to be collated into practical sized groups for sale, as well as protecting them from dirt, damage and moisture uptake from the atmosphere. Transportation from the oven exit to the point of packaging is typically of a significant distance which involves the use of multiple and long conveyors. In most cases, different types of cookies and biscuits that are produced freshly baked from the oven will be packed using different packaging machines. Through the introduction of diversion and curved conveyors, the biscuits may be taken to the appropriate location. It is therefore inevitable that the biscuits and cookies will end up cooling during this transportation phase.

The rule of thumb with regards to cooling times on open conveyors ranges from 50 – 200% of the baking time. In certain instances, biscuits may be immediately stacked following removal from the oven band. Thereafter, they may be cooled on wire conveyors which have fans blowing air from below or within forced convection tunnels with or without refrigerating the product. Proper handling of baked biscuits and cookies is important so as to ensure that the product is not exposed to damage due to dropping or jumbling together.

Long cooling conveyors will typically involve transfer and turnover between the exit of the oven and the final destination of the product. With the increased mechanization of cookie and biscuit production, it has become increasingly important to maintain the uniform orientation of the product on the oven band to the handling machines before wrapping occurs. A messed-up position would reduce the efficiency of the handling mechanisms. The longer the cooling conveyor is, the more the number of transfer points, and the more jumbled up biscuit positioning gets. It is therefore important to allow for minimal cooling and transportation before packaging of the product occurs.


Photo: Houdijk Holland

Freshly baked biscuits and cookies are pushed by successive rows of product onto the first cooling conveyor and they end up falling onto a cross conveyor. The first cooling conveyor is typically quite short and may be constructed out of cloth fabric or wire mesh. It is possible to retract the nose piece of the conveyor immediately behind the oven stripping knife of fingers.

This way, the bad or burnt biscuits can fall down onto a cross conveyor and get collected for scrap. The entire unit in which the product undergoes cooling is referred to as the oven stripper and is powered by the oven drive. This unit typically has a speed that is slightly faster than the oven band, thereby allowing for a degree of separation between the biscuit and cookie rows.

Cooling Conveyor & Stacker Machine

The cooling conveyor is constructed out of a modular design and connected together for the formation of the desired length. Supported side channels are typically fabricated from thick sheet. Idle rollers are spaced apart on conveying direction and return direction accordingly. The idle rollers are typically mounted on deep groove ball bearings with a grinding finish and are hard chrome plated to promote hygienic production conditions. To minimize the droppings of oil from the cloth during the production of high fat biscuits, all tie angles in the unit are replaced with idle rollers. Drive drums are included and projections are made on the drum surfaces for purposes of minimizing slip, or covered with friction grip rubber tape.

There is also tracking and manual tensioning available in the unit. To stack the oil sprayed product, use the feeder table as it will not need any more traveling following the oil spraying process. The oil spray machine is utilized to spray fine edible oil onto the top and bottom of hot biscuits emerging from the oven before being transferred to the cooling conveyor. The cookie or biscuit that emerges from the tripping conveyor is directed onto the cooling conveyor for purposes of transferring heat in the biscuit into the atmosphere as it passed on it. The recommended total travel of cooling conveyors is 1.5 times the length of the oven.

Potential Problems and Solutions

  • Baked Product Catches Fire – The oven band may stop during production due to say power failure. It would then be necessary to move it using a handle or an auxiliary power source. There is normally a short delay before the oven band is again moved, and this happens rather slowly. Under these conditions, the baked goods may catch fire after emerging from the oven. To prevent this, ensure that the hot product does not end up falling onto the canvas cooling conveyors which could lead to ignition and spreading of fire. A wire mesh oven stripper or conveyor is ideal as it provides a safe buffer from which the burning product can be swept onto the floor into the right containers.
  • Difficulty Stripping Product from the Band – Most short dough cookies and biscuits are soft and flexible as they emerge from the oven, which makes them much more difficult to strip from the band. Cooling soon enables setting of the sugary structure, therefore enough oven band run out after the oven is required for this to naturally occur. If this cannot be done naturally, then air must be blown down onto the product to accelerate the cooling or setting process. In certain instances, the band may be deliberately cooled with a unit that sprays water on the underside.
  • Product Breaks – When your baked biscuits or cookies break after removal from the oven, cooling and packaging, this is referred to as checking. This problem may be caused mainly as a result of moisture equilibration during the cooling process. As such, the wetter parts of the product contract while losing moisture and other drier parts expand. This creates tension that leads to cracking. In such a case, simply allow the product to cool for an additional few minutes before handling. Furthermore, there should be a low moisture gradient between the edge and centre as the biscuits leave the oven.

Photos by

houdijk cooling and handling

 

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