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The importance of coffee bean preservation throughout the entire process

From the roaster machine to the blending system

During the roasting phase, the coffee undergoes a physical and chemical transformation. It increases in volume – twofold – and becomes very fragile. This means we have to take particular care in handling it, avoiding any breakages as much as we can, whether the coffee is packed in beans or ground for capsules and single-serve applications.

“Breakages are very negative for our customers. The reasons can vary, from the poor image of the coffee stored inside the classical transparent hopper in a coffee shop, to important aroma preservation factors. In addition, if the coffee is ground, it is important for the beans to get to the grinder intact, to guarantee an even grinding process without segregating the product and de-mixing the coffee powder, which leads to an alteration in particle size distribution” says Maurizio Mazzoni, R&D Engineer at IMA Coffee Petroncini

What happens to the coffee beans after the roasting process?

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How coffee is properly conveyed in the next phases?

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What about storaging silos?

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Why roasted coffee weighing is so important in the process?

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How we can gently blend the coffee?

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What happens to the coffee beans after the roasting process?

“Just after the roasting phase, the coffee is cooled down and passes through destoning. The destoning phase after roasting is a common and effective solution for separating the coffee from stones, due to the high-density-difference between roasted coffee and other heavier materials” Mazzoni says.

The destoning phase can be handled in different ways depending on the overall production and plant layout. For medium and high productions, the traditional solution is to supply a destoner.

For small outputs, there are different solutions. The easiest one is a small destoner complete with a suction system: a tank collecting foreign bodies and a roasted coffee tank into which the clean product is discharged.  The second consists of a destoning carriage commonly combined with self-suction storaging silos, says Mazzoni.  This solution is very effective for customers who want to store the coffee in storaging silos near the roaster. The sliding carriage collects the coffee after it is discharged from the roaster and the suction system allows the coffee to be channelled through a dense pipe connected to the silos, which are in a vacuum to facilitate aspiration, he states. The carriage can slide onto different aspiration points so that the coffee can be redirected to the desired silo.”

“These solutions are equipped with fall shock absorbers and suction speed control to preserve the integrity of the beans” he declares.

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How coffee is properly conveyed in the next phases?

“The first step after roasting and destoning is weighing. The coffee needs to be weighed to check what shrinkage occurred during the roasting phase (this usually is between 14% and 20%).  Weighing after roasting is normally done with a batch weighing system. After that, the coffee must be sent to the storaging silos and there are different solutions for handling this phase” he explains.

“Mechanical conveyors are a common solution for conveying coffee to the top of the silos. When the distance between the two stations is small, we use a bucket elevator filled with coffee beans for gentle conveying without any breakages:

For a longer distance, approx. 30 metres, the best solution is a tubular drag conveyor, or chain conveyor, says Mazzoni, which consists of a closed pipe with a tensioned chain inside that moves a “train” of pucks: the space between one puck and the other is filled with coffee and the conveyance action is done by pushing the coffee from every puck.

“This system can gently convey the beans, avoiding almost all breakage or at least reducing it to a negligible percentage while preserving the aroma” Mazzoni says.

“The third type of conveying is the pneumatic. It can be done by aspiration or by compression. The great flexibility of application, such as elbows, inclined pipes, the option of fixing it to the ground or to the ceiling, multiple discharges and 2-way valves, means different routes can be installed inside the production area, bypassing any constraints even where there is an existing production complex “, he continues.

“Petroncini has developed the TPA system® which guarantees pneumatic product handling for up to 60 m of suction pipes, with less than 3% breakage, states Mazzoni . This system definitely requires less maintenance than mechanical conveyors.”

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What about storaging silos?

Above the silo storaging tower, there is a rotating distributor that automatically sends the coffee into a predetermined silo cell. The choice of cell can be made each time by the operator or it can be fully automatic depending on the plan for complete traceability of the coffee batches.

“In this phase, it is extremely important to preserve the integrity of the beans. We usually say that we give our beans a parachute, because a fall of more than 500 mm risks damaging them. Inside every silo and every silo cell, we use some special devices to gently escort the coffee during its fall. Some counter-mounted chutes or spiral descents prevent the coffee from impacting too hard. There are different types of shock absorbers, also designed to avoiding product obstruction especially considering the high production capacity of up to 5 tons per hour” Mazzoni says.

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Why roasted coffee weighing is so important in the process?

The batch weighing system is the most accurate dosing coffee system for creating blends according to specific needs. “In the Petroncini system, accuracy is guaranteed by three loading cells and the management of the conical valves. Using a pneumatic actuator that works on a vertical axis, these valves allow for volume optimisation. By working in three positions: open, closed and “fine dosing”, this system is able to guarantee an accurate dosing process” Mazzoni says.

Dust-tightness by way of suction avoids product contamination and keeps the working area clean. Easy maintenance and self-cleaning are guaranteed by compressed air injection.

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How we can gently blend the coffee?

Generally, if a company processes many coffee varieties, the blending phase is crucial to guarantee product homogenisation. The beans coming from different silo cells are mixed and then sent to the packaging lines for coffee bean bag preparation or to the grinders to be ground.

“Petroncini provides two types of blending machines combined with a batch-weighing system. The traditional solution is the horizontal mixer with rotating drum, equipped with helicoidal paths moving the product back and forth to perfectly mix the beans.” he affirms.

A more advanced solution is a batch auto-cleaning blender, Mazzoni says, suitable for companies that sell roasted coffee beans in bags or for specific hygiene requirements. In this case, the suction system combined with special mechanical components inside the mixer means small pieces of coffee can be removed from the blended product.

For those who do not want to blend their coffee, one solution for removing all the dust and the small pieces found the roasted coffee is to install an aluminium drum cleaner. The right inclination of the blades and the rotating speed control of the drum guarantee the effectiveness of this process.

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