Does Coffee Bean Storage Temperature Change the Aroma in the Cup?

How does coffee’s aroma change between opening a bag of beans and finishing it? Even if the beans’ aroma compounds change, the same changes will not necessarily be perceived in a brewed cup.

In 2024, Magdalena Gantner and colleagues stored opened beans at 5°C and 20°C for one month, then examined changes in volatile compounds and the aroma and taste of espresso and cold brew prepared from them. The aim was to investigate how storage temperature, coffee type, and brewing method relate to the beans’ compounds and the experience of drinking the coffee.

Storing Opened Beans at Two Temperatures for One Month

The study used three commercially available roasted coffees: 100% Arabica, 100% Robusta, and a blend of 80% Arabica and 20% Robusta. They were stored unopened at room temperature until the study began, and the packages were opened one month after roasting. Measurements taken immediately afterward served as the baseline. The remaining beans were divided into sealed bags and stored for a further month either under refrigerated conditions at approximately 5°C or at room temperature, approximately 20°C.

Thus, “before storage” or “day 0” in the paper means the time when the factory packaging was opened, not immediately after roasting. It was also the beans, not brewed coffee, that were stored for one month. The experiment addressed a period of storage after opening, such as in the home.

First, volatile compounds released by the beans were analyzed with an “electronic nose” using fast gas chromatography. Measurements were performed three times under each condition. Trained assessors then evaluated beverages brewed from beans kept under the same storage conditions. They rated 30 attributes, including aroma, flavor in the mouth, taste, astringency, body, and overall sensory quality.

In the sensory evaluation, each sample was assessed twice, and the mean of 18 evaluations in total was calculated. The number 18 refers to evaluations, not to 18 participants.

The Compounds Did Not Simply Decrease: Their Profile Changed

The analysis reported 44 volatile compounds across the three coffee types: 41 in Arabica, 34 in Robusta, and 44 in the blend. These numbers describe what the analytical method detected, not every compound contributing to coffee aroma.

After one month of storage, the compound profiles had changed at both temperatures. For example, the paper’s discussion explains that the relative proportion of 2-furanmethanol, a furan found in roasted coffee, increased after storage, with a smaller increase at 5°C. However, when Table 2 is examined by coffee type, the smaller increase at 5°C applies to Arabica and the blend. For Robusta, the values are 19.56% at 20°C and 20.24% at 5°C, and both carry the same significance letter. Thus, this table does not indicate a statistically significant difference between storage temperatures for Robusta. Storage-temperature differences were also found for aldehydes and other compounds, and the authors conclude that, overall, cooler storage suppresses changes.

What was measured here was each separated compound’s peak as a relative proportion of the total. An increase in a compound’s proportion does not necessarily mean its absolute amount increased: the proportion can also change when other compounds decrease. These results are not a retention rate showing “what percentage of the total aroma remained,” but changes in the balance of compounds making up the aroma.

Cold Brew from Cool-Stored Beans Tended to Resemble Coffee Prepared Just after Opening

For cold brew, water was added to coarsely ground beans, which were extracted at 5°C for 24 hours and then filtered. The beverage was also evaluated at approximately 5°C. Bean-storage temperature and the temperatures used to extract and evaluate the beverage are separate conditions.

Cold brews made from Arabica and Robusta stored at 20°C were rated higher in smoky and earthy aromas than samples prepared just after opening or after storage at 5°C. For example, Arabica’s smoky aroma on a 0–10 scale was 1.81 immediately after opening, compared with 3.35 after storage at 20°C and 1.64 after storage at 5°C.

Principal component analysis, which combines many assessed attributes to map similarities between samples, also showed that cold brews from beans stored at 5°C had profiles relatively close to the freshly opened samples. Those stored at 20°C occupied separate positions with different characteristics. The authors interpret this as evidence that cool storage helped preserve the original aroma and taste characteristics in cold brew.

However, the cool-stored samples did not remain unchanged in every attribute. For example, Arabica stored at 5°C received a lower sweet-aroma rating than it did immediately after opening. Nor were there clear differences in overall odor intensity between samples. Storage effects appeared as combinations of individual characteristics, not simply as a uniform weakening of aroma.

For Espresso, Even Cool Storage Did Not Preserve the Pre-Storage Profile

Espresso was prepared in an automatic coffee machine, extracting a total of 80 mL from 20 g of beans, and evaluated at approximately 60°C. For this brewing method, the overall sensory profiles tended to differ from those immediately after opening, whether the beans had been stored at 5°C or 20°C. The two groups stored at different temperatures showed similar characteristics to each other.

Changes included tendencies toward stronger sourness and rum-like flavor. However, not every attribute differed for every coffee. No statistically clear differences in overall sensory quality were demonstrated between samples. In these results, a changed profile needs to be distinguished from an overall decline in quality.

There were also differences associated with the brewing method itself. In comparisons using beans just after opening, espresso was associated with coffee-like characteristics and roasted, smoky, and chocolate notes, while cold brew was associated with sweetness and fruity and rum-like notes. However, grind size, extraction time, extraction temperature, and serving temperature all differed, so the effect of any single factor cannot be isolated.

Evaluating Storage Needs to Extend through Brewing

The authors explain that suppression of chemical reactions and changes in compounds at low temperatures could help preserve aroma. However, this study did not directly measure individual reaction rates or the progress of oxidation.

An important feature of the research is that storage was not assessed solely by analyzing beans: the investigation extended to sensory experience in the brewed beverage. Even with beans stored in the same way, cold brew retained characteristics closer to the original, whereas espresso changed differently. The authors argue that judging a storage temperature requires considering how the coffee will be brewed and which aromas and tastes one wants to preserve.

At the same time, the volatile compounds analyzed were those released by the beans; compounds in the beverages were not measured in the same way. The authors propose that analyzing both beans and brewed beverages in subsequent work could explain in greater detail how post-opening storage translates into aroma in the cup.

Can These Findings Be Applied Directly to Home Storage?

This comparison involved three commercial samples sealed and stored for one month. Information on bean origins and detailed roasting conditions was not obtained from the supplier, so the findings do not necessarily apply to every variety or roast level. Conditions such as opening and closing the bags daily, repeatedly moving them in and out of a refrigerator, or freezing were not compared.

Because the assessors were a trained panel, the findings do not directly show which coffee ordinary drinkers would like best. They cannot establish a single optimal storage temperature or duration for the home, but they provide concrete evidence for examining post-opening storage together with brewing method.

The research was supported by research funding from the Polish Ministry of Science and Higher Education through an institute at Warsaw University of Life Sciences. The authors declared no conflicts of interest.

Summary

After opened coffee beans were stored for one month, the balance of volatile compounds changed at both 5°C and 20°C. Cool storage tended to suppress changes, and in cold brew in particular, aroma and taste profiles closer to those immediately after opening were retained. In espresso, however, even cool storage did not maintain the same profile as immediately after opening.

The authors show that storage temperature alone does not determine the aroma in a cup: the coffee type and brewing method also matter. To understand how well aroma has been preserved, it is important to evaluate both the compounds in stored beans and the sensory qualities of coffee actually brewed from them.

References

Gantner, M., Kostyra, E., Górska-Horczyczak, E., & Piotrowska, A. (2024). Effect of Temperature and Storage on Coffee’s Volatile Compound Profile and Sensory Characteristics. Foods, 13(24), 3995. DOI: 10.3390/foods13243995 · Original full text.

© 2024 by the authors. CC BY 4.0.