Introduction:In 2021, Shanghai experienced a peculiar phenomenon where the entire city was filled with the aroma of coffee overnight. This incident, initially mistaken by the public as a fragrance factory leak, unexpectedly sparked discussions about the chemical components of coffee aroma and the sensory atmosphere of urban life. This article reviews the details of the event, analyzes the possible chemical substances that could produce such an aroma, and supplements the topic with some basic knowledge on identifying coffee aromas to help readers better understand the intricacies of coffee flavor.

In the early hours of May 17, 2021, residents in multiple districts of Shanghai shared a strange experience on social media platforms — the air was filled with a rich scent of coffee in the middle of the night. Some suspected their neighbors were brewing coffee late at night, others thought family members had secretly been sipping coffee, and some even wondered if they were hallucinating.

This mysterious aroma made people furrow their brows, as it didn’t resemble the pure scent of typical pour over coffee. Instead, it carried hints of burnt notes and sesame oil, similar to the profile of certain instant coffees on the market.

Subsequently, online rumors suggested that a fragrance processing factory in Minhang District might have had a gas leak, with the leaked substance speculated to be “furfuryl mercaptan” — an organic compound commonly used in food flavoring.

In fact, furfuryl mercaptan is a substance with a strong coffee aroma and sweet, caramel-like tones. In the field of fragrance formulation, it is often used to simulate the aromatic characteristics of coffee and chocolate. At appropriate concentrations, it can create an enticing roasted flavor. However, when leaked in large quantities, it may also mix with other odors, causing public concern.

In response to the incident, Shanghai’s fire and ecological environment departments quickly stated that they had not received any reports of factory accidents or incidents of explosions, combustion, or obvious gas leaks. Although relevant authorities had launched investigations, no abnormalities were found on-site, and the source of the aroma remained under investigation.

It is worth noting that at the time, Shanghai already had nearly 8,000 coffee shops, making it one of the cities with the highest coffee shop density in the world. The city’s growing passion for coffee meant that the “city-wide coffee aroma” incident drew particularly widespread attention.

According to multiple netizens, the smell of coffee began to appear around midnight on May 17. Not only was it intense, but it was also widespread, with reports of similar scents coming from areas ranging from Pudong to Minhang. Some initially suspected their home coffee machines had turned on by themselves during the night, while others called neighbors to ask if they too were enjoying a late-night coffee session.

But as more and more people reported the same experience, the suspicion grew that this might not be coffee aroma from homes, but rather a large-scale atmospheric dispersion phenomenon.

It was later confirmed that despite rumors of a fragrance factory accident, the fire department had not received any reports of incidents from factories in Minhang District, and most businesses were inactive that night, adding further mystery to the event. The Ecological Environment Bureau also stated that after arriving on-site, staff did not detect any unusual odors. They are currently working with multiple districts to further verify and investigate, striving to identify the true source of the aroma.

The above content is compiled by CoffeeHunters, a coffee news website.