An Overview of the Whole Process
In a pod weighing seven grams, even a small deviance from the normal blend is enough to produce big quality variations. In producing single-serve coffee, the consistency of the blend, the degree of the grind and the taste of each individual portion (which means each cup of brewed coffee) is crucial. Thus, in comparison to filter coffee, the reproducibility demands exacted on this product are even higher: The consumer of filter coffee levels out possible variations by brewing larger volumes.
Particularly in processing blends, the first steps prior to grinding are imperative for determining the quality of the final product. Primarily, the process of segregation must be prevented. With green and roasted coffee blends, segregation means an undesirable change of the defined mixing proportion. With coffee that has already been ground, segregation brings about a change in the desired grain spectrum. This means that the different plant components have to actively prevent segregation throughout the whole manufacturing process of single-serve coffee. This is the only way of ensuring that the originally desired blend that is produced actually ends up in the pod or capsule. Thanks to the high degree of automation, the influence of the operator, whose responsibility is focused more on monitoring quality, is minimized as far as possible. When coffee segregates during roasting, grinding or one of the conveyor paths, this has a major influence on the sensory perception of individual cups because of the small portions. Moreover, a basic prerequisite for a sensorial and qualitative first class single-serve product is, as is the case with all other forms of processing, a good green coffee. Its advantage lies in its low percentage of bad beans or beans afflicted by diseases or bugs. Particularly in this segment, bad beans have a considerable impact on the taste of individual portions.
Consistent Roasting Results in spite of Variable Quality
For consistent roasting results, the quality of the green coffee should not vary too strongly between batches. As coffee is a natural product, the same sort from the same plantation does not always mean the same quality. In order to offset the differences triggered by external factors such as moisture or ambient temperature, Probat has developed a technology called reflexion roasting (Reflex Automatic). This function controls the heat flow within the coffee bean during the development of the beans' temperature. It thus reacts to the fluctuating green coffee qualities during roasting. Particularly producers of highly sensitive coffee products such as single-serve, stand to benefit from this technology. Reflex Automatic identifies the difference between the actual and the set temperature curve. Based on this, the function automatically adjusts the amount and the temperature of air and thus reproduces the desired product temperature curve. Despite fluctuating green coffee qualities and external conditions, the function thus contributes to the production of qualitative and sensor-consistent coffees.
On the way from the roaster to the grinder, pneumatic or mechanical conveyor systems prevent segregation of the beans if the mix has been produced prior to roasting (blending before toasting) or prior to grinding (blending before grinding).
Ground Coffee: Automatic Monitoring of Grain Spectrum
At the very latest step, segregation must be prevented after grinding to ultimately get the same amount of coffee in all individual portions. Even if you are not processing a blend, you have to conserve the desired grain spectrum after grinding. Every single-serve system has its characteristic and predefined grain spectrum. Thus, the grinding process has to produce exactly the ratio of fine, medium and coarse that has been defined and optimized for the specific preparation system. If not, you would recurrently produce divergent results. Based on extensive tests and data collection, Probat's research and development department has developed the system of inline grain measurement to continually control the grain spectrum and thus decisively contribute to quality assurance.
It identifies variations in the grinding process induced by abrasion and wear of the grinding rolls and warns the operator and adjusts the rolls to automatically react to the variations. In contrast to the standard sampling at regular intervals, the system monitors grain size continually and directly. The ground product passes through a particle-measuring sensor mounted at the outlet of the roll mill.
A product sample is sucked from the ground coffee stream, diluted/aerated and channeled past an optical measuring device. Using a laser beam, this measures the particles' speed and flying time. The system compares the measured data with a maximum and minimum threshold value. If the sample moves beyond these values, the system alarms the operator who can then manually intervene. Computer-controlled grinders automatically adjust the grinding gap based on the data collected. After completing the data measurement, the system returns the product sample to production.
A consistent grain spectrum is the decisive criteria for the ensuing conveyance of the ground coffee. As only a small amount of ground coffee can be put into each single portion it is particularly important to have a consistent distribution of grain sizes. Therefore, preventing segregation into individual groups is crucial - the different grain sizes could group together into large, medium and small. A suction-impulse conveyor with the help of a conveying gas prevents segregation through a suction-impulse conveyance. The conveying gas has residual oxygen content of less than 1% and ensures an aroma-friendly product conveyance to the storage area.
Silos Ensure Consistent Results
Although silos play a small role during coffee processing, they play a major role for quality assurance and an optimal production flow. The system prevents segregation during the separating process between conveyance and ground coffee storage. The coffee is separated evenly without air movements whirling up fine particles and without causing zoning. The subsequent storage in the silo depends on the final product and the concomitantly planned dwelling or degassing time. Certain capsule systems are filled with a certain degree of excess pressure - in this case no complete degassing of the coffee takes place prior to packaging. Other systems, however, require completely degassed coffee, as it would otherwise bloat the package. Gastight silos with integrated sockets for degassing and pressure equalization provide for a targeted handling of ground coffee degassing.
The constructive design of Probat's silos is especially adapted to the characteristics of ground coffee. Together with a non-stick coating this prevents effects such as ground coffee deposits and kernel flow. The extraction method using a rocking bottom provides for a consistent extraction height of the ground coffee. In this way, consistently unvarying product gets to the individual single-serve portions according to the first-in/first-out principle. The last prerequisite for reproducible quality in the production process is the packaging machine, which transports the right amount of coffee into the pod or the capsule.
Controls for a Flexible and Lean Production
Reproducibility and minimized operator influence: These requirements are the benchmarks for an automated and efficient production of high quality single-serve coffees. A smooth production flow is particularly important when using capsules: As the producer fills these with a certain excess pressure, the time of packaging has to be precisely planned and carried out with regard to ground coffee degassing. In addition, the plant has to be flexible in terms of batch sizes and product change in order to be able to react to the requirements of demand, production and logistics. The plant control Pilot Plant Professional functions as an order-related data management system and provides this flexibility in combination with the roaster and the other components: It is able to process the different data as well as support production planning and thus provides for lean production processes.
Especially with regard to single-serve, "lean production" plays a decisive role. This means that the control is ideally suited for this application. Moreover, it can communicate with overarching ERP systems ("enterprise resource planning"). This ensures an ideal interplay of those departments involved in production and thus makes ideal use of production resources. And reduction of stock and "production on demand" are effective, quickly repaying cost-cutters. Good coffee alone is not a guarantee for a high quality single-serve product und neither is good plant technology. What is important is the perfect interplay of all of these factors in combination with the know-how of the roasting operation.
Thomas Koziorowski, is director research & development for Probat.