Fresh coffee from another galaxy?
- Krzysztof Blinkiewicz
- Apr 28
- 8 min read
A long time ago, in a galaxy far, far away, coffee roaster from a race unknown to Earth roasted coffee beans to make a cosmically better espresso. Traces of DMS and DMDS reached Earth and were detected by our scientists.
Hey, coffee roasters—what if space discoveries could help you improve your coffee freshness and better understand it? Imagine coffee from a distant planet, K2-18b, and alien roasters brewing their cosmic brew. Let’s have some fun with this thought!
Space Discovery: K2-18b and Its Potential to Harbor Life
Astronomers just took a thrilling new look at K2-18 b, a distant potential "Hycean" world — a planet thought to be covered in oceans and cloaked in a hydrogen-rich atmosphere. Using the JWST's mid-infrared eye (MIRI), they discovered intriguing hints of dimethyl sulfide (DMS) and dimethyl disulfide (DMDS) — molecules that, on Earth, are primarily produced by life. Their spectral fingerprint stood out strongly, suggesting these gases exist at high levels in K2-18 b’s atmosphere. While not a smoking gun for alien biology yet, this detection adds to a growing case that K2-18 b could host a habitable environment beneath its thick skies. More observations will be needed to confirm whether these biosignature candidates really hint at life, or if exotic, abiotic chemistry is at play. Either way, the search for life beyond Earth just got a lot more exciting.
Read about the discoveries made by Professor Nikku Madhusudhan's team at the Institute of Astronomy, University of Cambridge. Research paper: New Constraints on DMS and DMDS in the Atmosphere of K2-18 b from JWST MIRI
Admittedly, as critics point out, there are several major “buts” surrounding Professor Madhusudhan's team's research. First, it is not at all certain whether K2-18b is a water planet with a rocky surface surrounded by an atmosphere, or whether it is rather a “mini-Neptune,” a tiny “gas giant,” or perhaps a lava planet.
The reliability of the detection of both chemical compounds has been questioned because the statistical confidence level, or 'sigma,' is just 3-sigma. This means there is a 0.3% chance that the detected signal could be a random fluctuation, not an actual trace of these substances. In contrast, 5-sigma is the gold standard in scientific research, meaning the detection would be extremely reliable, with only a one-in-a-million chance of being a false signal.
Finally, critics say that while DMS and DMDS are markers of life on our planet, this does not necessarily have to be the case everywhere in the universe. We will therefore look at how it is formed on Earth, bearing in mind that on other objects it may be formed as a result of some inorganic, geological process that we do not know about.
Okay, we don't know for sure yet if there are DMS and DMDS on a planet 124 light years away from us, but we know where they come from on Earth - from coffee! And you deal with them every day, because they are also in roasted coffee, where they play a crucial role!
Dimethyl sulfide (DMS) is mostly made by marine life — especially phytoplankton (tiny ocean plants).These organisms produce a compound called DMSP (dimethylsulfoniopropionate) as part of their normal life processes — it's like a cellular "antifreeze" or stress protection. When phytoplankton die or get eaten (say, by zooplankton), DMSP breaks down — and one of the products is DMS gas, which then escapes into the atmosphere. What interests us even more is that it is formed in green coffee during the ripening of coffee berries, fermentation, and drying.
Dimethyl disulfide (DMDS) can form from DMS in the air or in certain biological environments. In the atmosphere, DMS reacts with oxygen or other chemicals, creating DMDS and other sulfur compounds. It can also be produced by bacteria — especially bacteria that break down sulfur-containing organic material in low-oxygen places, like swampy mud or rotting plants. I'll explain it to you in a moment, but it is also created in another way—during the roasting of coffee and its storage after roasting.
When news of the potential discovery of life on K2-18 b hit the media, one of the leading coffee researchers, joked on Instagram that it might not be plankton aliens, but someone just roasting coffee. This joke inspired me to write this article and reminded me of the research on coffee freshness conducted by the team of professor Chahan Yeretzian from ZHAW Zurich University of Applied Sciences.
Dimethyl Sulfide and Dimethyl Disulfide: From Space to Coffee Roasting
Let’s take a step back to reality. Coffee quality is a multifaceted variable that encompasses not only its flavor profile but also its freshness. In today’s fast-paced world, many coffee roasters are racing to get freshly roasted coffee to consumers as quickly as possible, thanks to express courier services. Freshness is just as crucial as it is often incomprehensible. This is where scientists come in, studying how to recognize coffee freshness, its benefits, and the negative effects of coffee that’s "too fresh" or past its prime—and when exactly does it become "old"?
While we all agree, according to the quality paradigm, that coffee should be fresh (however we define that), today we’ll focus on the factors that have a substantial impact on it.
“Once roasting is completed, a multitude of physical and chemical processes immediately start, leading to an evolution of the coffee over time. Indeed, a freshly roasted coffee is a highly elusive product. Among the many changes that occur over time after roasting, two are of particular importance and related to the quality attributes of coffee. One is the evolution of the aroma profile and the other the degassing of the beans. Once roasting is complete, the clock starts ticking on both of these processes.”
For many years, Prof. Yeretzian’s team searched for a method to monitor changes in the aroma composition of roasted coffee. The conclusions were as follows: processes and factors such as the following play a significant role in changes in freshness:
volatility,
internal reactivity,
oxidation.
Their research showed that dimethyl disulfide (DMDS) and methanethiol (MeSH) are reliable indicators of coffee freshness.
First of all, dimethyl sulfide (DMS) is present in green coffee because sulfur-containing molecules are broken down through biosynthetic and microbial processes. During coffee fermentation and drying, microorganisms can produce small volatile sulfur compounds, including DMS, as metabolic by-products.
DMS itself is highly volatile but sufficiently stable to survive green coffee processing. During roasting, its concentration typically increases further due to Maillard and Strecker degradation reactions.
Compound | Odor | Volatility | Reactivity |
Dimethyl disulfide (DMDS) | Sulfur, onion, garlic, burnt rubber | Medium | Medium |
Methanethiol (MeSH) | Sulfur, rotten egg, fish, cabbage, garlic, cheesy | High | Very high |
Simultaneously, methanethiol (MeSH) is produced during roasting from methionine degradation. MeSH is highly reactive and, in the presence of even small amounts of oxygen or metal ions (such as ferrous (Fe²⁺) and cupric (Cu²⁺) ions), it oxidizes to form dimethyl disulfide (DMDS).
After roasting, DMDS can accumulate if oxidative reactions continue or can degrade further into compounds such as dimethyl trisulfide (DMTS) or DMS under certain conditions.
Key points to remember:
MeSH is a breakdown product of the amino acid methionine and easily oxidizes to DMDS. Over time, the MeSH content degrades dramatically, often within a few days after roasting, while DMDS remains relatively stable and even continues to increase at room temperature over longer storage periods.
Thus, the DMDS/MeSH ratio rises over time and serves as an effective indicator of coffee freshness: the higher the DMDS/MeSH ratio, the "older" the coffee. Moreover, DMDS can further react to form DMTS or DMS. Environmental factors such as humidity and elevated storage temperatures (e.g., 50°C) can accelerate these reactions significantly.
In summary, monitoring the DMDS/MeSH ratio provides a valuable tool for assessing coffee freshness: loss of freshness = increase in DMDS, decrease in MeSH.
The research methodology used by Professor Yeretzian's team is very interesting. You can learn more about it in the following scientific article: Protecting the Flavors—Freshness as a Key to Quality.
Coffee Freshness and Its Cosmic Parallels
Some practical Tips for coffee roasters. During one of the lectures, scientists from ZHAW emphasized the importance of properly packaging coffee to preserve its freshness. Here are some key takeaways based on their research:
Package Immediately After Roasting: It's crucial to package your coffee in appropriate bags with valves right after roasting (of course cooling). Avoid storing coffee in large boxes, as many roasters do, because this can lead to quicker degradation of freshness.
Store Coffee at Lower Temperatures: Research has shown that storing your coffee beans in the refrigerator can significantly extend their peak freshness. While freshly roasted beans typically last 1–4 weeks at room temperature, refrigerating them can stretch this period to 3 months or even up to a year.
Understand the DMDS/MeSH Ratio: Pay attention to the DMDS/MeSH ratio, which is a reliable indicator of coffee freshness. If possible, monitoring this ratio helps you determine the best time to brew your coffee for optimal flavor.
By following these tips, you can maintain the freshest possible coffee, whether you're roasting it on Earth or looking to prevent cosmic coffee staleness on K2-18b!
Thanks to such research, we have a better understanding of the coffee storage process, we can design more appropriate packaging materials and capsules, and manage storage (at the temperature at which we store coffee) and transport. We also know why “too fresh” coffee may not taste good to us and when it may become “too old.” This knowledge also allows us to create new and better standards.
Perhaps, just like us, the aliens on K2-18b are grappling with their own ‘coffee freshness crisis.’ Maybe they have a planet-wide debate over the best storage methods for their roasted beans. Could their poor storage practices have caused the same sulfur buildup in their atmosphere? Maybe it's not just life they're discovering out there, but the universal struggle of all races to keep their coffee fresh! After all, whether on Earth or across the universe, there’s a shared cosmic dilemma of preserving that perfect cup.
From the mysterious gases on K2-18b to the role of sulfur compounds in our favorite drink, we've learned that whether it's space exploration or coffee roasting, there's a surprising connection.
So, next time you're brewing a cup of coffee, think about this cosmic connection — whether it's a freshly roasted bean from Earth or a hypothetical alien roaster from K2-18b, we're all trying to preserve that perfect, aromatic cup.
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