Course:FNH200/Projects/2024/Preservation of Coffee

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Introduction

Figure 1:Roasting coffee beans[1]

Coffee, buna, or bunn, originated in Ethiopia[2] and was believed to be a sacred plant used by mystics and their associated sacred ceremony[1], which helped them maintain consciousness during long prayers[3]. Coffee is now produced around the globe in many countries with different notes of flavor and accompanied by varying traditions. Whether Coffee is consumed as a cup in the morning while reading the news or after the extensive Ethiopian tradition, it has become a cultural phenomenon. Coffee is a significant worldwide market, with the top 3 leading exporters in 2022 being Brazil, Vietnam, and Indonesia.[4] North America is also a large consumer of this commodity; as of 2023, North America consumed 30.9 Million 60-kg Coffee bags.[5] Due to this worldwide market, it is necessary to preserve the quality and sanitation of these products for worldwide transport and storage until consumption.

Storage

Figure 2: Illustration showing the process that the coffee beans have gone through from picking to analysis.

Storage is essential for coffee in the post-harvest period. Immediately, the maximum storage period is determined to minimize quality loss and allow the producers to receive the most profit from their harvests[6]. Storage methods differ depending on whether the coffee is still green or has been roasted. Storage conditions such as packaging permeability, natural or washed, and temperature can change the Free fatty acid (FFA) content, water activity (WA), and Volatile Organic Compounds (VOCs)[7]. The above changes affect the beans' taste, texture, and aging speed.

Techniques for Preservation

Hulling:

One method involved in the processing of coffee is hulling. This refers to the removal of the outer layer of the coffee bean and it varies depending on if it is wet or dry processed[8]. For dry processed coffee beans, the entire dried husk (exocarp, mesocarp, and endocarp) is removed and for wet processed coffee, it is just the parchment layer (endocarp) that is removed[8]. The purpose of hulling is two-fold; not only does it cut down on costs by reducing the amount of product transported, reducing freight costs and increasing storehouse capacity, but it can also improve quality for brewing[6]. A study conducted in 2023 evaluated the influence of hulling on maintaining coffee quality. They found that hulled beans can have quality conserved for up to 12 months when stored under refrigerated conditions, and for 3 months when in a non-controlled environment[6]. They also found that mechanical hulling actually caused damage and reduced the quality of coffee beans in storage[6]. Manual hulling prevented damage and allowed the beans to be less susceptible to effects from ambient air, preserving the quality[6].

Figure 3: Example of a desiccant being used to control moisture levels and preserve quality.[9]

Desiccants:

The use of desiccants is a common practice in the preservation of coffee. Desiccants work by absorbing excess moisture that may have permeated through the packaging[10]. Controlling moisture, and thus humidity, helps preserve quality and prevent mould growth[10]. A recent study examined the efficacy of commercially available desiccants for the preservation of green coffee. They found that desiccants can be effective in preserving proper moisture-content, water activity, and colour when placed inside hermetic packaging[10]. This refers to airtight and sealed packaging. However, the desiccants were ineffective without the hermetic packaging[10]. Additionally, there were no differences found between the various desiccants used[10].

Preservation Methods for Coffee after Opening the Package

Figure 4:The 4 preservation methods employed after the opening of coffee packages.[11]

As we discussed earlier, coffee is one of the most consumed products globally and it goes through a complex processing before it’s sold to customers. The aroma of the coffee which many consumers enjoy and marks its freshness is not from the green coffee beans; on the contrary, the coffee gains its aroma only when it goes through a process called roasting.[12] During roasting, extreme chemical and physical changes happen to coffee; amino acids react with sugars through Millard Reaction and cause many volatile organic compounds to form.[11] In roasted coffee, approximately 30 organic compounds are responsible for giving coffee its distinctive aroma.[13] From the time of roasting, the aroma of the coffee undergoes chemical and physical changes and is not completely stable hence the importance of preservative methods.[11] Those changes are divided into two categories, one is the loss of CO2 gas (called degassing) and the other is degradation of organic compounds (mostly through oxidation with O2) responsible for coffee’s aroma.[11] The process of degassing starts right after roasting and continues for a months after and degeneration of organic compound starts right after roasting.[11] Therefore, packaging with good barrier materials that keeps O2 gas out of the package and allows for release of CO2 from the inside the package is the principal behind coffee packaging.[11] This is accomplished by using one valve package system that allows for one way release of CO2 from inside and prevent O2 from entering the packaging.[11] Once the coffee package is opened, preservation advantages offered through controlled environment is lost. Since many consumers do not use the whole content of the coffee in one setting, and some taking months to finish it, maintaining freshness becomes a challenge.[11] In one study, that looked at preservation methods after opening of coffee packages on secondary shelf life of coffee, four methods of preservations were employed (as illustrated in Figure 3):[11]

1-Screw: the use of a closed system employing screw caps. [11]

2- Clip: a clip was used to close the packaging. [11]

3- Tape: after opening a tape was used to close the opened package.[11]

4- Canister after opening of the package, the beans were transferred to a metal Canister.[11]

This study showed that the customer behavior can influence the preservation of coffee after the packaging is opened.[11] In this study, freshness indices using GC/MS (Gas Chromatography/ Mass Spectrometry) measured the evolution of 2-butanone/2-methyl furan above the headspace of coffee beans as a quantitative method to measure freshness.[11] Out of the four techniques employed, the use of a screw cap was associated with better preservation since it showed the slowest loss of aroma indicator (2-butanone/2-methyl furan) over time.[11]

Preservation of Coffee Pods and Sustainability

Demand for convenience and innovation, as well as lifestyle changes, has driven a rapid growth in the coffee pod market. Coffee pods are made of a single serving of ground coffee that is compressed and packaged into a in flat or round paper containers and sealed in airtight foil to create a protected environment.[14] These pods provide way of preparing relatively good coffee quickly, which is quite popular among customers. Nevertheless, these impermeable foils are not recyclable because they contain aluminum, and therefore environmentally unsustainable.[14] As a result, the industry is searching for a more sustainable alternative to resolve this issue.

Figure 5: Percentage of oxygen in the headspace of coffee pods packaged with standard (STD) and recyclable (REC) multilayer films and stored at 25 °C for 12 months.

Recyclable polypropylene multilayer film is an alternative that has been investigated.[14] Recent research suggests that this material, compared to the standard aluminum-based film, provides better protection against oxygen, moisture, and oxidation over a year-long storage period.[14] In addition, polypropylene multilayer film requires lower grammage (81 vs. 99 g/m2), which ultimately reduced the amount of waste.[14] Furthermore, all samples preserved in the polypropylene multiplayer packaging were all accepted by the costumers, without any significant difference in comparison to the standard packaging.[14] Therefore, polypropylene multilayer film packaging could a considered a viable and sustainable alternative to the standard packaging.[14]

Exam Questions

Which of the following are techniques used for the preservation of coffee?

a) Controlled storage

b) Desiccants

c) Closing packaging after it is opened

d) All of the above


Answer: d) All of the above


Why should this question be on the exam: This would be a good question for the final exam because it touches on some of the topics mentioned throughout the course. The use of controlled atmospheric storage, drying agents, and packaging are important techniques used for the preservation of coffee as well as a variety of other foods.

References

  1. ↑ 1.0 1.1 "10 steps from seed to cup [Internet]. [cited 2024 Aug 5]. Available from: https://www.ncausa.org/About-Coffee/10-Steps-from-Seed-to-Cup". External link in |title= (help)
  2. ↑ "The Spruce Eats [Internet]. [cited 2024 Aug 5]. Ethiopian coffee culture - legend, history and customs. Available from: https://www.thespruceeats.com/ethiopian-coffee-culture-765829". External link in |title= (help)
  3. ↑ "Sacred brews: a history of coffee and religion [Internet]. [cited 2024 Aug 5]. Available from: https://www.magellantv.com/articles/sacred-brews-a-history-of-coffee-and-religion". External link in |title= (help)
  4. ↑ "List of countries by coffee production. In: Wikipedia [Internet]. 2024 [cited 2024 Aug 5]. Available from: https://en.wikipedia.org/w/index.php?title=List_of_countries_by_coffee_production&oldid=1231534050". External link in |title= (help)
  5. ↑ "December 2023 Coffee Report and Outlook [Internet] International Coffee Organization; 2023 Dec [cited 2024 Aug 5]. Available from: https://icocoffee.org/documents/cy2023-24/Coffee_Report_and_Outlook_December_2023_ICO.pdf" (PDF). External link in |title= (help)
  6. ↑ 6.0 6.1 6.2 6.3 6.4 "Abreu GF, Rosa SDVF, Coelho SVB, Pereira CC, Malta MR, Fantazzini TB, et al. Influence of hulling and storage conditions on maintaining coffee quality. An Acad Bras Ciênc [Internet]. 2023 Dec 11 [cited 2024 Aug 6];95:e20190612. Available from: https://www.scielo.br/j/aabc/a/fzTSBCGGNYDkmvx4WnjqjcH/". External link in |title= (help)
  7. ↑ "Błaszkiewicz J, Nowakowska-Bogdan E, Barabosz K, Kulesza R, Dresler E, Woszczyński P, et al. Effect of green and roasted coffee storage conditions on selected characteristic quality parameters. Sci Rep [Internet]. 2023 Apr 20 [cited 2024 Aug 6];13:6447. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10119118/". |first= missing |last= (help); External link in |title= (help)
  8. ↑ 8.0 8.1 "10 steps from seed to cup [Internet]. [cited 2024 Aug 8]. Available from: https://www.ncausa.org/About-Coffee/10-Steps-from-Seed-to-Cup". External link in |title= (help)
  9. ↑ "Serious Eats [Internet]. [cited 2024 Aug 11]. Why you should keep desiccants packets in your kitchen. Available from: https://www.seriouseats.com/desiccants-packets-kitchen-uses-7377381". External link in |title= (help)
  10. ↑ 10.0 10.1 10.2 10.3 10.4 "Anokye-Bempah L, Han J, Kornbluth K, Ristenpart W, Donis-González IR. The use of desiccants for proper moisture preservation in green coffee during storage and transportation. Journal of Agriculture and Food Research [Internet]. 2023 Mar 1 [cited 2024 Aug 8];11:100478. Available from: https://www.sciencedirect.com/science/article/pii/S2666154322002113". External link in |title= (help)
  11. ↑ 11.00 11.01 11.02 11.03 11.04 11.05 11.06 11.07 11.08 11.09 11.10 11.11 11.12 11.13 11.14 11.15 "Smrke S, Adam J, Mühlemann S, Lantz I, Yeretzian C. Effects of different coffee storage methods on coffee freshness after opening of packages. Food Packaging and Shelf Life [Internet]. 2022 Sep 1 [cited 2024 Aug 10];33:100893. Available from: https://www.sciencedirect.com/science/article/pii/S2214289422000850". ELSEVIER. External link in |title= (help)
  12. ↑ "Dorfner R, Ferge T, Kettrup A, Zimmermann R, Yeretzian C. Real-time monitoring of 4-vinylguaiacol, guaiacol, and phenol during coffee roasting by resonant laser ionization time-of-flight mass spectrometry. J Agric Food Chem [Internet]. 2003 Sep 1 [cited 2024 Aug 10];51(19):5768–73. Available from: https://pubs.acs.org/doi/10.1021/jf0341767". Journal of Agricultural and Food Chemistry. External link in |title= (help)
  13. ↑ "Mayer F, Czerny M, Grosch W. Sensory study of the character impact aroma compounds of a coffee beverage. Eur Food Res Technol [Internet]. 2000 Sep 1 [cited 2024 Aug 10];211(4):272–6. Available from: https://doi.org/10.1007/s002170000169". European Food Research and Technology. External link in |title= (help)
  14. ↑ 14.0 14.1 14.2 14.3 14.4 14.5 14.6 "Calabrese M, Luca LD, Basile G, Lambiase G, Romano R, Pizzolongo F. A recyclable polypropylene multilayer film maintaining the quality and the aroma of coffee pods during their shelf life. Molecules [Internet]. 2024 Jun 1 [cited 2024 Aug 10];29(13):3006. Available from: https://www.mdpi.com/1420-3049/29/13/3006". Molecules. External link in |title= (help)
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