Medidas Físicas y Sensoriales en la Preparación del Café

Prof. William Ristenpart

Parte 1:¿Cuál es el Centro de Café?

Parte 2:Medidas Físicas y Sensoriales del Café

Sacramento (Davis) está situado en la costa oeste

28,000 estudiantes de pregrado,en 104 especialidades

6,600 estudiantes de posgrado

1 de 10 Campus universitarios en California, pero solo campus con ciencia de los Alimentos

Famoso por las bicicletas, y la sostenibilidad ambiental

Hay muchos hispanos y personas que hablan español

U.C. Davis es ya un líder mundial en Vino y ciencia de la alimentación (Robert Mondavi Institute)

Lab 1 – Reverse Engineering a Drip Coffee Brewer

Lab 2 – Process Flow Diagram and Mass Balances for Coffee

Lab 3 – The pH of Coffee and Chemical Reactions

Lab 4 – Measuring the Energy Used to Make Coffee

Lab 5 – Mass Transfer and Flux during Brewing

Lab 6 – Coffee as a Colloidal Fluid and the Effect of Filtration

Lab 7 – First Design Trials: Optimizing Strength & Extraction

Lab 8 – Second Design Trials: Scaling Up to 1 Liter of Coffee

Lab 9 – Design Competition and Blind Taste Panel

An

alys

isD

esig

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The Design of Coffee: An Introduction to Chemical Engineering

3 units: Lecture – 1 hour; laboratory – 2 hours. Non-mathematicalintroduction to how chemical engineers think, as elucidated bythe process of roasting and brewing coffee. Qualitative overviewof the basic principles of engineering analysis and design.Corresponding laboratory experiments testing the effect of designchoices on the sensory qualities of coffee.

2013 2014 2015 2016

Coffee Lab renovated, begins serving 500 students / quarter

UC Davis Coffee Initiative established

Design of CoffeeFreshmen Seminar

(18 students)

Establishment of the Coffee Center

Peet’s Coffee provides a

founding gift

2017

Donations from severalmore forward-thinking

companies and individuals from the

coffee industry…

2018

Green Bean Storage

Laboratory

Brewing & Espresso

Laboratory

Patio

PilotRoastery

6000 sq. ft. of space, dedicated as a home for coffee science research

and advanced education

BehmorStudent Space

JosumaMeeting

Space

Metabolomics& Nutrition

ZivkovicSlupsky

Sociology &Cultural Studies

Biltekoff Kyle TaylorBio-Ag Engineering

Donis-Gonzalez

Fan

Bottling &Food Safety

Bamforth Harris

Sensory & Consumer Science

Guinard Heymann

Genetics

Cantu Medrano

Chemistry

Barile

German Lebrilla

Mitchell

Plant Science

van Deynzes Brown

Aerosol Science

Wexler Zhang

Microbiology

Marco Mills Boundy-Mills

Sustainability& Efficiency

Schladow Simmons Spang

AgriculturalEconomics

Boucher Kiesel Sexton

Chemical Engineering

Boulton

Kuhl Runnebaum

Ristenpart

Greenwood

Law, IP, &Regulatory

ScowTomich

Parte 1:¿Cuál es el Centro de Café?

Parte 2:Medidas Físicas y Sensoriales del Café

Earnest Earl Lockhart

ca. 1940 (Antarctica)

ca. 1960 (Coffee Brewing Institute)

http://www.scanews.coffee/2013/10/04/the-coffee-brewing-institute/

Nice historical article by Emma Sage regarding the CBI:

Two Key Metrics for Every Brew

Total Dissolved Solids (TDS)

How much soluble coffee

is actually in our drink

(also known as “strength”)

Percent Extraction (PE)

How much of the soluble coffee

was removed from the grounds

(also known as “yield”)

≈ 20%

≈ 1.5%

The Coffee Brewing Control Chart

(Lockhart, 1960s)

The numbers in the chart can be derived from mass balance arguments(lots of equations!)

Ted Lingle, ca. 1990

http://www.scanews.coffee/2013/10/04/the-way-we-were-specialty-coffees-first-decade/

Nice historical article by Donald Schoenholt re early SCA :

Ted Lingle et al.

Number 1 book sold by SCA

The Coffee Brewing Control Chart Needs Technical Updating

Standard brew charts are not

temperature corrected for density

Difficult to account for mass

loss via CO2 offgassing

Implicit assumption about 𝑅𝑎𝑏𝑠 inaccurate values

• Chart is based on

percolators! (Mr.

Coffee was invented

in the 1970s)

Chart pre-dates drip brewers

(Mr. Coffee was invented in the 1970s)

• Chart is based on percolators! (Mr.

Coffee was invented in the 1970s)

Chart ignores chemical reactions

Chart conflates sensory descriptive

with hedonic sensory judgements

(these are not the same!)

Sharp dividing lines falsely imply minor

changes portend huge differences

The Coffee Brewing Control Chart Needs Sensory Updating

Sensory data was based on 1950s housewives

(not representative today)

Preliminary “warm-up” project:What is better for drip brewing,

flat bottom or conical?

Discrimination Testing• Triangle tests

• Treatments 2x2 design

• Four total treatments

• Flat Bottom, Conical

• Two grind settings – Mahlkönig Guatemala

• Setting 3 (finer) and Setting 4 (coarse)

• 6 total pairs were compared

• 45 participants, each tasting all 6 in random order

Raw Triangle data….

Flat Bottom

Grind 4

Conical

Grind 4

Flat Bottom

Grind 3

Conical

Grind 3

SIG - 25/45

SIG – 23/45

SIG – 33/45

P < 0.001

SIG – 22/45

P=0.048

X X

p = 0.004

NS – 18/45

P = 0.292

p = 0.024

NS – 15/45

P = 0.394

Main conclusion:

Basket shape matters more than grind size!

Molly Spencer, grad student at UC Davis who analyzed and designed the new coffee

flavor wheel

Descriptive AnalysisOverview:

1. Define your product set

2. Convene a panel of judges

3. Attribute generation• Judges are blind to the product

treatments

• Presented the Coffee Lexicon/

Wheel

• Panel leader remains impartial

• All vocab is panel generated

4. Vocabulary alignment through

reference standards

Aroma IngredientFloral/ Chamomile Chamomile tea, dry

Smoke/ Acrid Wright’s Liquid Smoke MesquiteFlavorBerry Private Selection Triple Berry Preserves

Dried Fruit Mixture of Sun-Maid Prunes and Prune JuiceRaisin Sun-Maid RaisinsCitrus Fresh lemon juice

Whiskey Jack Daniel’s Tennessee WhiskeyDark Green/ Veg equal parts juice green bean : spinach : asparagus

Hay-Like McCormick Parsley FlakesMusty/Dusty Kretschmer Wheat Germ

Earthy Miracle-Gro Potting Mix soilTobacco Camel cigarettes (Turkish and Domestic blend)

Brown Roast C&H Pure Cane Sugar, Golden BrownGrain/ Malt Equal parts Rice Chex, Wheaties and Quaker Quick Oats

Brown Spice Equal parts cinnamon : nutmeg : cloveHazlenut Roast hazelnut oilAlmond Raw almond sliversMolasas Grandma’s Original Molasses, unsulphured, in water

Chocolate Toll House semi-sweet morselsCocoa Hershey’s Cocoa Powder Natural Unsweetened, in waterWood popsicle sticks

Burnt Wood/ Ash wood ashRubber rubber bands

Raw Descriptive Analysis Data

Principal Component Analysis of Descriptive

Lr = Light Roast

Dr = Dark Roast

Co = Conical

Ba = Flat Bottom

3 = Grind 3

5 = Grind 5

Roast

Geometry

Grind

Principal Component Analysis of Descriptive

The sensory data clearly show the basket geometry makes a difference.

The key question is: ¿por qué?

Absorption ratio – Analogy with Paper Towels

Paper towels absorb water…but only a finite amount.

The more paper towels you use, the more water you absorb:

𝑅𝑎𝑏𝑠 = mass of absorbedwater

mass of dry paper towels

Dry coffee grounds also absorb water… and only a finite amount

𝑅𝑎𝑏𝑠 = mass of absorbed water

mass of dry coffee grounds

Did differences in absorption ratio affect the brew?

Short answer: Almost definitely yes!

Flat Bottom Conical

3 5 3 5

1.50

1.75

2.00

2.25

G rind S etting

reta

ine

d w

ate

r (g

)/ d

ry c

off

ee

(g

)

DarkL ight

Flat Bottom Conical

3 5 3 5

1.50

1.75

2.00

2.25

G rind S etting

reta

ine

d w

ate

r (g

)/ d

ry c

off

ee

(g

)

DarkL ight

𝑃𝐸 = 𝑇𝐷𝑆 × (𝑅𝑏𝑟𝑒𝑤 − 𝑅𝑎𝑏𝑠)

Fractionation of the Brew(i.e., a brew profile)

Conical: sharp increase then decreaseFlat: sharp decrease then gradual increase

Conclusions (flat vs. conical matters a lot!)

In progress:Brew profiles and fractionation (physical measurements)Core sampling for extraction yield, correlate with tempHedonic (liking) sampling of consumers (flat vs. conical)Most important: Mapping entire brewing parameter space

?

Many thanks to our sponsors!

Acknowledgements

Finally, muchas gracias to Anacafé for the invitation!

Dr. Scott Frost Mackenzie Batali Prof. Jean-Xavier Guinard

Importancia Sensorial de la Extracción del Café en la Cadena de ConsumoProf. William Ristenpart, UC Davis Coffee Center

Raúl Roda, Paradigma / Onyx Coffee

Juan Luis Alvarado, Anacafé