Coffee is one of the most consumed beverages in the world. However, issues such as climate change threaten the growth of the temperature-sensitive Coffea arabica plant, more commonly known as Arabica coffee. Therefore, it is crucial to make beverages more efficient by using less coffee while still meeting the high demand for the beverage. Here, we explore pour-over filter coffees, in which a water jet impinges on a water layer above a granular bed. To reveal its internal dynamics, we first substitute opaque coffee grounds with silica gel particles in a glass cone, imaged with a laser sheet and a high-speed camera. We discover an avalanche effect that leads to strong mixing at various pour heights, even with a gentle pour-over jet. We also find that this mixing is not significantly impacted by a layer of floating grains, which is often present in pour-overs. Next, we perform experiments with real coffee grounds to measure the extraction yield of total dissolved solids. Together, these results indicate that the extraction of the coffee can be tuned by prolonging the mixing time with slower but more effective pours using avalanche dynamics. This suggests that instead of increasing the amount of beans, the sensory profile and the strength of the beverage can be adjusted by varying the flow rate and the pour height. In this way, the extraction efficiency could be better controlled to help alleviate the demand on coffee beans worldwide.
REFERENCES
1.
Statistics Section,
Coffee Report and Outlook (CRO)
(International Coffee Organization
, 2023
).2.
A. J. T. M.
Mathijssen
, M.
Lisicki
, V. N.
Prakash
, and E. J. L.
Mossige
, “Culinary fluid mechanics and other currents in food science
,” Rev. Mod. Phys.
95
, 025004
(2023
).3.
C.-L.
Chen
, Y.-H.
Kuo
, and M.
Fang
, “Study on coffee flavour of various pour-over brews
,” Flavour Fragrance J.
38
, 3
–12
(2023
).4.
C.
Booth
, C.
Cummins
, M.
Dalwadi
, P.
Dellar
, M.
Devereux
, J.
Dewynne
, J.
Donohue
, A.
Duncan
, F.
Fitzmaurice
, A.
Gordon
, M.
Hennessy
, J.
Hinch
, C.
Hickey
, P.
Hjorth
, T.
Kyrke-Smith
, D.
Leahy
, W.
Lee
, E.
Lynch
, O.
Mercier
, S.
Miklavcic
, S.
Russell
, L.
Schwartz
, B. F.
Shozi
, P.
Swierczynski
, C.
Timoney
, J.
Tomczyk
, and E.
Warneford
, “Brewing of filter coffee
,” in Technical Report from MACSI's 2012 Problem-Solving Workshop with Industry
(Mathematics in Industry
, 2012
).5.
J.
Gagne
, Physics of Filter Coffee (Scott Rao Coffee Books, 2021).6.
Y.-W.
Lin
, W.-C.
Lu
, C.-H.
Liao
, and P.-H.
Huang
, “Innovative coffee filter cups enhance pour-over coffee quality while providing bioactive benefits - Challenges and opportunities
,” J. Agric. Food Res.
15
, 101024
(2024
).7.
K.
Fibrianto
, A. D.
Ardianti
, K.
Pradipta
, and W. B.
Sunarharum
, “The influence of brewing water characteristic on sensory perception of pour-over local coffee
,” IOP Conf. Ser.: Earth Environ. Sci.
102
, 012095
(2018
).8.
M. Y.
Rendón
, M. B.
dos Santos Scholz
, and N.
Bragagnolo
, “Physical characteristics of the paper filter and low cafestol content filter coffee brews
,” Food Res. Int.
108
, 280
–285
(2018
).9.
M.
Várady
, T.
Hrušková
, and P.
Popelka
, “Effect of preparation method and roasting temperature on total polyphenol content in coffee beverages
,” Czech J. Food Sci.
38
, 417
–421
(2020
).10.
J.
Wallace
, “An analysis of the acid profile of coffee brews: Caffeine and chlorogenic acid concentrations in different forms of coffee brew
,” Honors Theses
(University of Mississippi, 2017
).11.
S.
Angeloni
, A. M.
Mustafa
, D.
Abouelenein
, L.
Alessandroni
, L.
Acquaticci
, F. K.
Nzekoue
, R.
Petrelli
, G.
Sagratini
, S.
Vittori
, E.
Torregiani
, and G.
Caprioli
, “Characterization of the aroma profile and main key odorants of espresso coffee
,” Molecules
26
, 3856
(2021
).12.
S.
Andueza
, M. P.
de Peña
, and C.
Cid
, “Chemical and sensorial characteristics of espresso coffee as affected by grinding and torrefacto roast
,” J. Agric. Food Chem.
51
, 7034
–7039
(2003
).13.
L.
Navarini
, M.
Ferrari
, F. S.
Liverani
, L.
Liggieri
, and F.
Ravera
, “Dynamic tensiometric characterization of espresso coffee beverage
,” Food Hydrocolloids
18
, 387
–393
(2004
).14.
C. A.
Salamanca
, N.
Fiol
, C.
González
, M.
Saez
, and I.
Villaescusa
, “Extraction of espresso coffee by using gradient of temperature. Effect on physicochemical and sensorial characteristics of espresso
,” Food Chem.
214
, 622
–630
(2017
).15.
F. M.
Nunes
, M. A.
Coimbra
, A. C.
Duarte
, and I.
Delgadillo
, “Foamability, foam stability, and chemical composition of espresso coffee as affected by the degree of roast
,” J. Agric. Food Chem.
45
, 3238
–3243
(1997
).16.
S.
Andueza
, L.
Maeztu
, L.
Pascual
, C.
Ibáñez
, M. P.
de Peña
, and C.
Cid
, “Influence of extraction temperature on the final quality of espresso coffee
,” J. Sci. Food Agric.
83
, 240
–248
(2003
).17.
S.
Andueza
, M. A.
Vila
, M.
Paz de Peña
, and C.
Cid
, “Influence of coffee/water ratio on the final quality of espresso coffee
,” J. Sci. Food Agric.
87
, 586
–592
(2007
).18.
E.
Illy
and L.
Navarini
, “Neglected food bubbles: The espresso coffee foam
,” Food Biophys.
6
, 335
–348
(2011
).19.
M. I.
Cameron
, D.
Morisco
, D.
Hofstetter
, E.
Uman
, J.
Wilkinson
, Z. C.
Kennedy
, S. A.
Fontenot
, W. T.
Lee
, C. H.
Hendon
, and J. M.
Foster
, “Systematically improving espresso: Insights from mathematical modeling and experiment
,” Matter
2
, 631
–648
(2020
).20.
G.
Caprioli
, M.
Cortese
, G.
Sagratini
, and S.
Vittori
, “The influence of different types of preparation (espresso and brew) on coffee aroma and main bioactive constituents
,” Int. J. Food Sci. Nutr.
66
, 505
–513
(2015
).21.
J.
Giacomini
, G.
Khamitova
, P.
Maponi
, S.
Vittori
, and L.
Fioretti
, “Water flow and transport in porous media for in-silico espresso coffee
,” Int. J. Multiphase Flow
126
, 103252
(2020
).22.
A. N.
Gloess
, B.
Schönbächler
, B.
Klopprogge
, L. D.
Ambrosio
, K.
Chatelain
, A.
Bongartz
, A.
Strittmatter
, M.
Rast
, and C.
Yeretzian
, “Comparison of nine common coffee extraction methods: Instrumental and sensory analysis
,” Eur. Food Res. Technol.
236
, 607
–627
(2013
).23.
E.
Olechno
, A.
Puścion-Jakubik
, R.
Markiewicz-Żukowska
, and K.
Socha
, “Impact of brewing methods on total phenolic content (TPC) in various types of coffee
,” Molecules
25
, 5274
(2020
).24.
F. B.
Wadsworth
, C. E. J.
Vossen
, M. J.
Heap
, A.
Kushnir
, J. I.
Farquharson
, D.
Schmid
, D. B.
Dingwell
, L.
Belohlavek
, M.
Huebsch
, L.
Carbillet
, and J. E.
Kendrick
, “The force required to operate the plunger on a French press
,” Am. J. Phys.
89
, 769
–775
(2021
).25.
M.
Várady
, J.
Tauchen
, P.
Klouček
, and P.
Popelka
, “Effects of total dissolved solids, extraction yield, grinding, and method of preparation on antioxidant activity in fermented specialty coffee
,” Fermentation
8
, 375
(2022
).26.
A.
Santanatoglia
, M.
Cespi
, D. R.
Perinelli
, L.
Fioretti
, G.
Sagratini
, S.
Vittori
, and G.
Caprioli
, “Impact of the human factor on the reproducibility of different coffee brewing methods
,” J. Food Compos. Anal.
124
, 105698
(2023
).27.
C.
Gianino
, “Experimental analysis of the Italian coffee pot “moka
”,” Am. J. Phys.
75
, 43
–47
(2007
).28.
L.
Navarini
, E.
Nobile
, F.
Pinto
, A.
Scheri
, and F.
Suggi-Liverani
, “Experimental investigation of steam pressure coffee extraction in a stove-top coffee maker
,” Appl. Therm. Eng.
29
, 998
–1004
(2009
).29.
P.-M.
Binder
and C. B.
Scheidle
, “The Moka pot: Thoughts and experiments
,” Phys. Educ.
55
, 065024
(2020
).30.
W. D.
King
, “The physics of a stove-top espresso machine
,” Am. J. Phys.
76
, 558
–565
(2008
).31.
K.
Sanchez
and E.
Chambers
IV, “How does product preparation affect sensory properties? An example with coffee
,” J. Sens. Stud.
30
, 499
–511
(2015
).32.
K.
Calvin
, D.
Dasgupta
, G.
Krinner
, A.
Mukherji
, P. W.
Thorne
, C.
Trisos
, J.
Romero
, P.
Aldunce
, K.
Barrett
, G.
Blanco
, W. W.
Cheung
, S.
Connors
, F.
Denton
, A.
Diongue-Niang
, D.
Dodman
, M.
Garschagen
, O.
Geden
, B.
Hayward
, C.
Jones
, F.
Jotzo
, T.
Krug
, R.
Lasco
, Y.-Y.
Lee
, V.
Masson-Delmotte
, M.
Meinshausen
, K.
Mintenbeck
, A.
Mokssit
, F. E.
Otto
, M.
Pathak
, A.
Pirani
, E.
Poloczanska
, H.-O.
Pörtner
, A.
Revi
, D. C.
Roberts
, J.
Roy
, A. C.
Ruane
, J.
Skea
, P. R.
Shukla
, R.
Slade
, A.
Slangen
, Y.
Sokona
, A. A.
Sörensson
, M.
Tignor
, D.
Van Vuuren
, Y.-M.
Wei
, H.
Winkler
, P.
Zhai
, Z.
Zommers
, J.-C.
Hourcade
, F. X.
Johnson
, S.
Pachauri
, N. P.
Simpson
, C.
Singh
, A.
Thomas
, E.
Totin
, P.
Arias
, M.
Bustamante
, I.
Elgizouli
, G.
Flato
, M.
Howden
, C.
Méndez-Vallejo
, J. J.
Pereira
, R.
Pichs-Madruga
, S. K.
Rose
, Y.
Saheb
, R.
Sánchez Rodríguez
, D.
Ürge-Vorsatz
, C.
Xiao
, N.
Yassaa
, A.
Alegría
, K.
Armour
, B.
Bednar-Friedl
, K.
Blok
, G.
Cissé
, F.
Dentener
, S.
Eriksen
, E.
Fischer
, G.
Garner
, C.
Guivarch
, M.
Haasnoot
, G.
Hansen
, M.
Hauser
, E.
Hawkins
, T.
Hermans
, R.
Kopp
, N.
Leprince-Ringuet
, J.
Lewis
, D.
Ley
, C.
Ludden
, L.
Niamir
, Z.
Nicholls
, S.
Some
, S.
Szopa
, B.
Trewin
, K.-I.
Van Der Wijst
, G.
Winter
, M.
Witting
, A.
Birt
, M.
Ha
, J.
Romero
, J.
Kim
, E. F.
Haites
, Y.
Jung
, R.
Stavins
, A.
Birt
, M.
Ha
, D. J. A.
Orendain
, L.
Ignon
, S.
Park
, Y.
Park
, A.
Reisinger
, D.
Cammaramo
, A.
Fischlin
, J. S.
Fuglestvedt
, G.
Hansen
, C.
Ludden
, V.
Masson-Delmotte
, J. R.
Matthews
, K.
Mintenbeck
, A.
Pirani
, E.
Poloczanska
, N.
Leprince-Ringuet
, and C.
Péan
, “IPCC, 2023: Climate Change 2023: Synthesis Report. Contribution of Working Groups I, II and III to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change [Core Writing Team, H. Lee and J. Romero (eds.)]. IPCC, Geneva, Switzerland
,” Report No. 6 (Intergovernmental Panel on Climate Change (IPCC)
, 2023
).33.
M. A. G.
Ferrão
, E. M.
Riva-Souza
, C.
Azevedo
, P. S.
Volpi
, A. F. A.
Fonseca
, R. G.
Ferrão
, C.
Montagnon
, and L. F. V.
Ferrão
, “Robust and smart: Inference on phenotypic plasticity of Coffea canephora reveals adaptation to alternative environments
,” Crop Sci.
64
, 2709
–2724
(2024
).34.
F.
Vezzulli
, G.
Rocchetti
, M.
Lambri
, and L.
Lucini
, “Metabolomics combined with sensory analysis reveals the impact of different extraction methods on coffee beverages from coffea arabica and coffea canephora var. robusta
,” Foods
11
, 807
(2022
).35.
X.
Wang
and L.-T.
Lim
, “Effects of grind size, temperature, and brewing ratio on immersion cold brewed and French press hot brewed coffees
,” Appl. Food Res.
3
, 100334
(2023
).36.
J.
Eggers
and E.
Villermaux
, “Physics of liquid jets
,” Rep. Prog. Phys.
71
, 036601
(2008
).37.
P. G.
de Gennes
, “Granular matter: A tentative view
,” Rev. Mod. Phys.
71
, S374
–S382
(1999
).38.
R. P.
Behringer
and B.
Chakraborty
, “The physics of jamming for granular materials: A review
,” Rep. Prog. Phys.
82
, 012601
(2019
).39.
B.
Scheichl
, R. I.
Bowles
, and G.
Pasias
, “Developed liquid film passing a smoothed and wedge-shaped trailing edge: Small-scale analysis and the ‘teapot effect’ at large Reynolds numbers
,” J. Fluid Mech.
926
, A25
(2021
).40.
R.
Duarte
, A.
Pinheiro
, and A. J.
Schleiss
, “An enhanced physically based scour model for considering jet air entrainment
,” Engineering
2
, 294
–301
(2016
).41.
V.
Frette
, K.
Christensen
, A.
Malthe-Sørenssen
, J.
Feder
, T.
Jøssang
, and P.
Meakin
, “Avalanche dynamics in a pile of rice
,” Nature
379
, 49
–52
(1996
).42.
M.
Paczuski
, S.
Maslov
, and P.
Bak
, “Avalanche dynamics in evolution, growth, and depinning models
,” Phys. Rev. E
53
, 414
–443
(1996
).43.
M. L.
Hunt
and N. M.
Vriend
, “Booming sand dunes
,” Annu. Rev. Earth Planet. Sci.
38
, 281
–301
(2010
).44.
S. R.
Nagel
, “Instabilities in a sandpile
,” Rev. Mod. Phys.
64
, 321
–325
(1992
).45.
R.
Juanes
, Y.
Meng
, and B. K.
Primkulov
, “Multiphase flow and granular mechanics
,” Phys. Rev. Fluids
5
, 110516
(2020
).46.
C. S.
Campbell
, “Rapid granular flows
,” Annu. Rev. Fluid Mech.
22
, 57
–90
(1990
).47.
I.
Haviv
et al, “Amplified erosion above waterfalls and oversteepened bedrock reaches - Haviv - 2006
,” J. Geophys. Res.
111
, F04004
, https://doi.org/10.1029/2006JF000461 (2006
).48.
S.
Badr
, G.
Gauthier
, and P.
Gondret
, “Erosion threshold of a liquid immersed granular bed by an impinging plane liquid jet
,” Phys. Fluids
26
, 023302
(2014
).49.
D.
Ervine
, H.
Falvey
, and W.
Withers
, “Pressure fluctuations on plunge pool floors
,” J. Hydraul. Res.
35
, 257
–279
(1997
).50.
P.
Lertsawatwicha
and T.
Siriborvornratanakul
, “Measuring particle size distribution of ground coffee using computer vision
,” Int. J. Inf. Technol.
15
, 2961
–2967
(2023
).51.
N.
Xue
, S.
Khodaparast
, and H. A.
Stone
, “Fountain mixing in a filling box at low Reynolds numbers
,” Phys. Rev. Fluids
4
, 024501
(2019
).52.
J.
Schindelin
, I.
Arganda-Carreras
, E.
Frise
, V.
Kaynig
, M.
Longair
, T.
Pietzsch
, S.
Preibisch
, C.
Rueden
, S.
Saalfeld
, B.
Schmid
, J.-Y.
Tinevez
, D. J.
White
, V.
Hartenstein
, K.
Eliceiri
, P.
Tomancak
, and A.
Cardona
, “Fiji: An open-source platform for biological-image analysis
,” Nat. Methods
9
, 676
–682
(2012
).53.
M. E.
Batali
, W. D.
Ristenpart
, and J.-X.
Guinard
, “Brew temperature, at fixed brew strength and extraction, has little impact on the sensory profile of drip brew coffee
,” Sci. Rep.
10
, 16450
(2020
).54.
J. S.
Scheingross
and M. P.
Lamb
, “A mechanistic model of waterfall plunge pool erosion into bedrock
,” J. Geophys. Res. Earth Surf.
122
, 2079
–2104
, https://doi.org/10.1002/2017JF004195 (2017
).55.
A. S.
Goudie
, “Waterfalls: Forms, distribution, processes and rates of recession
,” Quaestiones Geographicae
39
, 59
–77
(2020
).56.
Y.
Liu
and J.-H.
Tay
, “State of the art of biogranulation technology for wastewater treatment
,” Biotechnol. Adv.
22
, 533
–563
(2004
).57.
G. G.
Fuller
, M.
Lisicki
, A. J. T. M.
Mathijssen
, E. J. L.
Mossige
, R.
Pasquino
, V. N.
Prakash
, and L.
Ramos
, “Kitchen flows: Making science more accessible, affordable, and curiosity driven
,” Phys. Fluids
34
, 110401
(2022
).58.
R. E.
Vieyra
, C.
Vieyra
, and S.
Macchia
, “Kitchen physics: Lessons in fluid pressure and error analysis
,” Phys. Teach.
55
, 87
–90
(2017
).59.
A. C.
Rowat
, N. N.
Sinha
, P. M.
Sörensen
, O.
Campàs
, P.
Castells
, D.
Rosenberg
, M. P.
Brenner
, and D. A.
Weitz
, “The kitchen as a physics classroom
,” Phys. Educ.
49
, 512
(2014
).© 2025 Author(s). Published under an exclusive license by AIP Publishing.
2025
Author(s)
You do not currently have access to this content.
