Exploring filter coffee extraction through different methods.

This research can be found in full form at the link: https://www.sciencedirect.com/science/article/pii/S002364382300049X

Coffee beverages, made with specialty coffees using filter brewing methods have become increasingly popular.

From an engineering perspective, coffee brewing is regarded as a solid-liquid extraction that takes place between hot water and ground coffee beans when the water passes through a bed of coffee grounds. The most important parameters, to keep under control during brewing, are coffee mass-to-water ratio, grind size and distribution, brewing time, water temperature, and agitation (Barroso et al., 2022). Coffee extraction is the final step in coffee production (see the free seed to cup course to learn more) and greatly influences the beverage's final form and properties. Among the different brewing methods used for specialty and filter coffee applications, drip methods (using a coffee cone and paper filter) such as immersion methods (ground coffee is immersed in water) have been proposed (Córdoba, Moreno, Osorio, Velásquez, & Ruiz, 2021). Recently, V60, French Press (FP) and AeroPress, have been the most common extraction methods for the development of filter coffee or long coffee. In fact, V60 is the traditional pour-over system, it's pouring hot water through coffee grounds in a filter paper; FP is the classical full immersion system, easily replicable, with mechanical filtration; while AeroPress uses pressure, it's appropriate for strong extractions, uses a paper filter. Pure BrewTM from Black Eagle Maverick (Victoria Arduino) is a novel three-phase extraction method, utilizing water pulses at programmed frequencies. The machine uses a Pure BrewTM coffee filter holder, co-developed with a micro-thin double-mesh conical filter that can contain up to 20 grams of coffee. By combining Pure Brew technology with the patented conical filter, filter coffee can be created at the touch of a button.

Therefore, my recent study aimed to investigate the differences between the newly developed filter coffee extraction method, Pure Brew (A), with traditional ones (V60 (B), French Press (C), AeroPress (D)) (Santanatoglia et al., 2023), in terms of particle size of the powders, physicochemical characteristics, extraction yields, volatile profile and bioactive compounds. To the best of our knowledge, this is the first paper where these parameters for filter coffee produced by the novel Pure Brew technique are studied. All analyses were carried out on three differently roasted coffees (i.e., light, medium and dark) to choose the most suitable coffee for each roast and bring the study as close as possible to the consumers.

Three different types of coffee, with different degrees of roasting were used for each brew method: specialty Don Cayito, white honey (Coffea arabica from Gardelli Specialty Coffee) for light roasting, specialty Kakindu, natural (Coffea arabica from Gardelli Specialty Coffee) for medium roasting and specialty 100% Arabica blonde roasted coffee (Coffea arabica from Starbucks) for dark roasting. Different coffees were selected to give as realistic a picture as possible of the “filter” and “specialty” coffee worlds.

A specific routine was used for each of the four brewing methods, delivering 250 ml of the final volume in the cup. Three replicates were prepared for each brewing method with each coffee.

Finally, the main results from UHPLC-MS/MS** analysis showed that Pure Brew is comparable to other methods available on the market, but also showed the highest levels of caffeine (598.28 ± 8.84 and 556.13 ± 1.22 μg/mL) and bioactive compounds (1726.8 ± 22.4 and 1407.89 ± 9.53 μg/mL) in medium and dark roasted coffee, compared to the other brewing methods. While for a light degree, the highest level of caffeine was detected in the FP method (734.72 ± 7.07 μg/mL). Concerning CGAs, 5-CQA (953.76 ± 7.06–577.45 ± 8.36 μg/ mL) was the most abundant compound discovered, followed by 3-CQA (278.39 ± 7.07–136.88 ± 2.56 μg/mL), and 3,5-diCQA (85.58 ± 3.41–20.23 ± 0.69 μg/mL), followed by caffeic acid (3.35 ± 0.21–1.30 ± 0.16 μg/mL). Figure 1

Figure 1. comparison of bioactive compounds resulting from different brew methods

Pure Brew also displayed the most positive results in extraction yields, it falls into the ideal extraction percentage (18–22%) at the three different degrees of roasting, versus the other brewing methods.

Figure 2

Figure 3

Figure 4

Figures 2,3,4 plot the brew methods on the brewing control chart with TDS on the y axis and extraction percentage on the x axis for light, medium and dark roasted coffees

From the HS-SPME/GC-MS* analysis at the light roast, for Pure Brew discovered the most olfactometrically impactful molecules of the study of volatile organic compounds, 5-Methyl Furfural (caramellic), Furfural (bready), and 2-Furanmethanol (burnt, caramel, cooked), connected with positive remarks, associated with sweet.

Figure 5 chemical structures of compounds associated with caramel (5-Methyl Furfural) and bready (Furfural) and burnt, caramel, cooked (2-Furanmethanol) flavour notes

Finally, principal component analysis was applied to evaluate the relationship between the different coffee extraction methods and the four coffee preparation methods at the three different degrees of coffee roasting. The score plot separates the preparation methods, with the different coffees used at three different roasting degrees; particularly the clustering of coffees according to the degree of roasting (light, medium, and dark). However, a defined trend cannot be found for the different types of extraction used (V60, FP, AP, and PB).

In this way, the three score plots clearly demonstrated the clustering of the four filter coffee extraction methods, in fact, AP and V60 were found to be significantly different from Pure Brew in all three coffee roasts. As regards FP, a significant clustering has been found in the light roast, while in medium and dark FP was quite like PB.

The similarity between the two coffees was due to the mechanical filter, whereas V60 and AP utilized a paper filter. FP showed a good extraction of non-volatile compounds, especially in the light roast, however, their extraction was lower than in PB. In conclusion, PB is closer to FP than to the other extraction methods, but PB displayed some differences with FP as it fits into the optimal extraction range at all three roasting levels, its preparation requires half time, and it results in a more balanced cup in terms of aroma/volatile molecules.

FIgure 6. Principle component analysis showing relationship between differet brew methods

In conclusion, a feature evaluation of an espresso machine that can make filter coffee (Pure Brew) has not been reported in any study. In the current work, we compared this new technique with the most known filter coffee methods (V60, French Press, and AeroPress) studying variables not evaluated before. The evaluation of these analyses could contribute to the commercial development of this new method of obtaining filter coffee (Pure Brew), which today is prepared mainly with the traditional techniques considered in our study. Based on these results and feedback about applications of Pure Brew there are benefits to using this system, compared with other methods. In addition to the qualitative results above, it is faster, and more consistent. It is possible to prepare espresso and filter coffee by utilising a single coffee machine, yielding a saving in cost and space occupied by equipment.

[_Agnese Santanatoglia

_](https://coffeeknowledgehub.com/en/member/61a49b77e7359a2985bde75f)

About the author: After earning a master’s degree in Pharmacy and Industrial Pharmacy in 2021, and a master in nutrigenomics in 2022, I qualified as a Pharmacist, and now I am carrying on an international PhD project in Food Analytical Chemistry at the University of Camerino, focused on Coffee Science.

_*HS-SPME/GC-MS= Headspace solid-phase microextraction (HS-SPME) coupled to gas chromatography–mass spectrometry (GC-MS) is widely employed for volatile analyses... _

_https://doi.org/10.3390%2Fmolecules23102436 _

_**UHPLC-MS/MS: UHPLC-MS/MS is connected in various research facilities for the qualitative and quantitative investigation of a pharmaceutical substance, pharmaceutical items, and biological specimen. _

_Rathod, R.H., Chaudhari, S.R., Patil, A.S. et al. Ultra-high performance liquid chromatography-MS/MS (UHPLC-MS/MS) in practice: analysis of drugs and pharmaceutical formulations. Futur J Pharm Sci 5, 6 (2019). https://doi.org/10.1186/s43094-019-0007-8 _

_REFERENCES:

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_2- Córdoba, N., Moreno, F. L., Osorio, C., Velásquez, S., & Ruiz, Y. (2021). Chemical and sensory evaluation of cold brew coffees using different roasting profiles and brewing methods. Food Research International, 141, 110141. https://doi.org/10.1016/j.foodres.2021.110141 _

_3- Santanatoglia A., Caprioli G., Cespi M., Ciarlantini D., Cognigni L., Fioretti L., Maggi F., Mustafa A., Nzekoue F. & Vittori S. (2023). A comprehensive comparative study among the newly developed Pure Brew method and classical ones for filter coffee production. LWT, 2023 _