Roast and aroma protection for the full coffee experience

During industrial coffee roasting, carbon monoxide levels can rise rapidly. Continuous monitoring of CO concentration ensures plant safety and can also provide indications of the degree of roasting. Gas analysis also plays a role in packaging to prevent aroma loss. Endress+Hauser contributes to coffee production with measurement applications for monitoring process parameters relevant to safety and quality.

Coffee is a universally popular beverage, which has improved enormously in recent years in terms of the variety of tastes, the range of production methods and the quality of the beans. There are no longer just the big coffee producers, but also more and more small coffee roasters who are trying to meet the sharp rise in customer demands. Due to the great variance in the required throughput of coffee beans, there are correspondingly different sizes of coffee roasting plants. Some are about the size of a car, others fill a large factory hall with the entire process.

Nevertheless, the roasting process is similar.

During this process, there is a high risk of a sudden rise in carbon monoxide (CO), which is a safety risk. It is therefore of great interest to the coffee roaster to detect such sudden CO increases very quickly so that action can be taken in a correspondingly short time.

When roasting, maximum concentration is required. With industrial roasting processes, the temperatures vary between 200 and 280 °C depending on the product, degree of roasting, and desired roasting color. When the coffee beans are dried during the roasting process, CO₂ and CO are given off alongside water and oils.

During the roasting of coffee beans, CO is produced, which only occurs in low concentrations at the beginning of the roasting cycle, but increases exponentially during the process. Thus CO can, if not observed, exceed the lower explosion limit, which the plant operator wants to prevent at all costs. This safety risk is eliminated by monitoring CO. By setting up low alarm thresholds, the roasting process can be stopped in time so that an explosive atmosphere is not created in the first place. Due to the rapid rise in CO concentration, an early response measurement is essential. The parchment skins of the coffee beans and waxy substances flying around in the process can quickly clog any filter or other gas treatment measures and are very difficult to remove.

However, precise measurement of CO concentration can serve another purpose: In some coffee-processing methods, the CO content is also used as an indicator of the correct roast level and, consequently, the desired aroma.

The GM901 gas analyzer measures carbon monoxide with the gas filter correlation optically directly in the channel and calculates the CO concentration in mg/m 3 or ppm - thus, increases of the CO concentration are detected within shortest time (around 10 seconds).

A purge air unit protects the optical interfaces on the sender and receiver unit from dust and dirt. Because of the coffee bean skins and wax-like substances in the process, the in-situ technology has proven its worth at this point. In-situ has no direct contact with these very sticky substances, which are difficult to separate in a gas treatment system.

The short response times that result from the quick in-situ measurement and the minimal maintenance requirements make the GM901 gas analyzer the obvious choice:

• Emission Monitoring: Continuous measurement of CO concentrations for process optimization
• Ensuring Safety: Continuous monitoring of CO levels with the GM901 prevents CO concentrations from exceeding the lower explosive limit. An early warning is issued if the limit values are exceeded.
• Hygiene and reliability: Thanks to in-situ technology, no part of the analyzer is in contact with the waxy substances, or the coffee bean husks released during the process.

The full flavor profile is also affected by the packaging: To preserve the coffee's aroma inside the package, oxygen must be removed from the coffee packaging as the taste will inevitably be lost if the oxygen content is too high.

Inerting is made easier thanks to fast and accurate laser oxygen measurement using the TRANSIC100LP laser transmitter. The oxygen content is measured directly at the packaging machine, and nitrogen is added as an inert gas.

Nitrogen is expensive - adjusting the system manually with inaccurate measurements is very inefficient and costly. Ideally, the process should be monitored so that it can be controlled appropriately. This can only be done when the oxygen measurement process provides quick and accurate results. 

Compared to electrochemical measurement cells, the TRANSIC100LP with laser technology performs outstandingly well. The rugged laser oxygen transmitter is easy to integrate. O₂ is measured accurately without noticeable time delays, errors, or alarms. The rapid measured value display ensures the nitrogen is controlled reliably, automatically, and without the need for any additional manual interruptions, whereas the process of measuring with the electrochemical cell had to be given much more attention.

With TRANSIC100LP, nitrogen can be saved, and maintenance costs will be lower. The transmitter is nonwearing, does not have any mechanical parts, and functions without consumables. In addition, it features outstanding tightness, meaning that incorrect measurements can be avoided.

• Fast measurement directly in the process
• Easy installation and operation
• Self-diagnostics with maintenance indicator
• No cross-sensitivity to particles, vibrations, or changes in flow rate
• Low operating costs: minimal consumables and no purge gas consumption
• Long-term stability; insensitive to humidity and temperature