The aroma of freshly roasted coffee is one of the most alluring yet most fleeting qualities. Coffee aroma begins to lose the moment it is roasted, so proper packaging and storage is required to maintain its freshness. So what kind of packaging can help us better lock in the aroma and maintain freshness?
The following content is quoted from “Effects of different coffee storage methods on coffee freshness after opening of packages” in ScienceDirect, Food Packaging and Shelf Life Volume 33, September 2022, 100893. In this article, the impact of different packaging on coffee storage was studied.
After a coffee package has been opened, the protective atmosphere changes, accelerating the loss of freshness and staling of coffee. This study compares four different methods for storing whole roasted beans after opening the package: (i) transferring beans into airtight canister, (ii) ) closing original package with tape, (iii) closing with clip and (iv) using a package with an integrated screw cap. The aroma was analyzed during storage by gas chromatography mass spectrometry (GC/MS), after grinding. Freshness indices were determined as ratios of GC/MS signal intensities of two selected compounds and used as indicators of storage stability (also called index), to compare different storage approaches. The 2-butanone/2-methylfuran index was found to be best suited to assess coffee staling for such conditions. The screw cap packaging was the best performing storage method. Using a clip, re-closing with tape or transferring beans into a container resulted in a faster loss of freshness. Findings were in line with observed changes in oxygen and carbon dioxide content inside the respective package.
Coffee is one of the most consumed beverages in the world, known for its unique aroma and refreshing effects. But green coffee beans are the seeds of the coffee tree and do not produce any aroma before being processed. The aroma of coffee is produced during roasting. Roasting causes dramatic changes in the chemical composition of the beans and their physical and sensory properties. Sugar reacts with amino acids through the Maillard reaction to form large amounts of volatile organic compounds (VOCs). In roasted coffee, about 30 compounds work together to create the characteristic aroma. Chemical reactions during the roasting process also cause physical changes; the beans become brown, dry, brittle, and porous.
From a food safety perspective, coffee roasted to a moisture content of less than 5% is a shelf-stable product. Still, freshly roasted coffee is not stable and the ingredients change after roasting. Chemical and physical changes that cause quality deterioration can be broadly divided into carbon dioxide loss and aroma degradation. Approximately 1% of the weight of freshly roasted coffee is carbon dioxide, which plays an important role in the formation of crema during the espresso brewing process. This gas release, also called outgassing, lasts for about a month. The large amount of gas released places strict demands on coffee packaging. The carbon dioxide needs to be vented and oxygen from the air prevented from entering the packaging. Technically, this is usually solved with a coffee one-way valve to prevent the package from breaking after inflation.
Many coffee aroma compounds are unstable or highly volatile, and their content in the beans steadily decreases after roasting. Using packaging materials with good barrier properties during the coffee packaging process and eliminating oxygen within the packaging can help prevent or slow down the oxidative degradation of coffee aroma, thereby reducing the loss of freshness.
Coffee freshness has been studied in the past from the perspective of chemical composition, taste, and odor. It is defined as coffee that retains as close to the quality of freshly roasted coffee as possible. The loss of freshness can be quantified by measuring the degassing process or analyzing changes in coffee aroma. Aroma analysis by GC/MS allows the freshness of coffee to be assessed by monitoring the loss of aroma compounds that are hallmarks of typical coffee aroma or by the appearance of compounds that indicate degradation/oxidation of coffee components. Aroma loss has previously been quantified as the sum of 2-methylpropionaldehyde, 3-methylbutyraldehyde, 2,3-butanedione, and 2-methylfuran and is known as the S-index. Holscher and Steinhart pointed out that methanethiol has a strong impact on aroma freshness, which decreases significantly after only one day of baking. Czerny and Schieberle reported that the aging of coffee is a result of the degradation of 2-furfurylthiol.
A simple way to assess compositional changes in the headspace (HS) above roasted coffee involves reference to the freshness index. The freshness index is the ratio of the signal intensities of two compounds selected from a single GC/MS chromatogram and is therefore less affected by instrument drift, which may affect the intensity of the GC/MS signal over time. Since the metric used is the ratio between the instrument signal intensities for two compounds in a single GC run, the method does not necessarily require calibration with standards.
So far, studies on freshness and aging losses have been conducted mainly during coffee’s main shelf life, that is, during storage in unopened packages. The main shelf life of coffee can be extended with appropriate packaging solutions. However, even the best packaging and anaerobic conditions cannot prevent the loss of freshness because coffee is an inherently unstable product. There is also secondary shelf life for reuse, but the purpose of this study was not to determine a threshold for secondary shelf life. Because this threshold is based on consumer acceptance, consumer perceptions of coffee aging are likely to vary among different consumer groups. Therefore, we investigated how different packaging methods and consumer habits affect the aging of coffee early in the secondary shelf life, based on an objective and measurable value (freshness index) and whether the aging rate can be reduced by improving coffee shelf life. conversion rate.
The five packaging treatments used in this study:
Reference sample, unopened packaging;
Screw caps, using encapsulated integrated closure systems;
Clips, used to seal packages;
Canning, where beans are transferred to a sealed metal container and beans are subsequently removed from the container each time;
Tape, seal the package with tape after each sampling.
See the figure below for specific research data.
This is the first systematic study of whole-bean coffee deterioration after unpacking and covers four major coffee-handling habits of consumers. It complements previous work on coffee shelf life research and sheds light on the main drivers of freshness loss. Both targeted and untargeted methods are used to determine the age of different stored coffees.
The study evaluated what happens to coffee from a chemical perspective during secondary shelf life and typical coffee processing conditions. The final results showed that integrated screw caps (with one-way valves) on the packaging best protected the coffee aroma.
Therefore, based on the research results of this article, coffee packaging bags with one-way ventilation valves are the best choice for packaging your roasted coffee beans.
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