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- Susan C. Jackels, Seattle University
- Charles F. Jackels, University of Washington, Bothell
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- Project Description
- How did this project develop?
- Partnership
- Objectives
- Coffee Processing Overview
- Field Study
- Plans for Future Work
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- 2000 - 2003 – ISJACHEM meetings (International Association of Chemists
from Jesuit Universities) Prof. Carlos Vallejos
- 2002 – Seattle University sabbatical application and research initiated
- 2002, 2003 – SU Mission Endowment Fund supported preliminary research
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- 2003 – March planning trip and partnership formed: UCA Managua, CRS/NI,
ADDAC. Prof. Janet Quillian
- 2003 – Preparation: Laboratory research at SU, Class on International
Development, Spanish classes
- 2003 – Charles Jackels joined as collaborator with sabbatical from UW,
Bothell
- January – February 2004 – Field study conducted
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- Study the coffee fermentation process
- Time-profiles of temperature and bio-chemicals
- Variations in profiles under different conditions
- Look for indicators of fermentation completion and quality
- Find and apply experimental methods that can be used on the farm
- Use the results of the fermentation study to design a simple test for
over-fermentation
- Help coffee farmers improve consistency and quality with a fermentation
test and training
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- Coffee cherries are picked by hand when fully ripe.
- Mature fruits are red or orange-yellow, depending upon the variety of
coffee plant.
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- Before leaving the farms, the outer layers of the cherries are removed and the beans are
partially dried.
- The layers removed include the outer skin and the soft pulpy tissue
beneath it.
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- In the Matagalpa region, partially dried beans are shipped by the farmer
to a “dry beneficio”, such as SolCafe near Sebaco.
- The beans are sun dried on patios for several days
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- With their water content reduced to 12%, the beans are stored by the dry
beneficio as “parchment coffee” until marketed.
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- At the time of sale, the parchment and silver skin layers are removed
mechanically, resulting in “coffee oro.”
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- Before being transferred to the dry beneficio for final drying and
storage, the farmer removes the outer skin and pulp and initiates the
drying process.
- In Nicaragua this is generally done by what is known as the “wet
process.”
- This process on the farm is crucial to achieving high quality
coffee. It must be initiated on
the same day that coffee is picked.
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- The coffee cherry is composed of
a hard bean surrounded by four distinct layers of pulp and skin
- The outer skin and soft pulp are removed by a “despulpadora” in the “wet
beneficio” on the farm.
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- Very thin layers known as silver skin and parchment remain as the beans
leave the farm.
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- The despulpadora mechanically removes the outer skin and pulp.
- Widely varying amounts of water are used.
- Pulps are ejected from one side.
- Beans emerge from the other.
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- A mucilage layer strongly adheres
to the depulped beans and must be removed before drying.
- The mucilage is carbohydrate and consists of a pectin structure with
simple sugars.
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- The depulped beans are placed in a fermentation tank for a period of
from 8 to 24 hours.
- Tanks vary greatly in size and construction.
- Fermentation proceeds by enzymes
and microorganisms that are present naturally.
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- At completion of fermentation, the mucilage is loosened from the beans
such that it can be removed by washing.
- The traditional test is to insert
and remove a stick from the beans.
If they do not slide over
each other to refill the hole,
fermentation is judged complete.
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- The fermented beans are washed with prodigious amounts of clean flowing
water.
- The mucilagenous material now completely washes off, and
- Defects, such as pieces of pulp, are separated by floatation and are discarded.
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- The washed beans are dried in the sun on the farm for 1-2 days and then
are shipped to dry beneficio for complete drying and processing.
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- It is generally thought that
fermentation is critical to coffee quality.
- Both over and under fermentation result in a degraded product and a
lower market price. The
traditional test for completeness is subjective and nonpredictive.
- The biochemistry of fermentation is complex and not well understood,
involving enzymatic, bacterial, and yeast processes.
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- 50 mL sample of beans (about 115 beans)
- Add 50 mL water and mix thoroughly
- Perform test on the resulting aqueous suspension
- Measurements were made every 2-4 hours throughout the fermentation
process.
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- When the farmers determined that the fermentations had proceeded
sufficiently, final sets of tests
were made.
- Completion of fermentation was then
bracketed by the last two sets of tests. This bracket varied from 1-3 hours.
- Of the quantities measured, pH was found to correlate best with the fermentation process.
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- Quantitative (ReflectoQuant©)
- pH
- Lactic Acid
- Glucose
- Alcohol
- Qualitative
(color strip tests)
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- pH appears to track well the fermentation process.
- Lactic acid concentrations increase rapidly as completion is approached
only for the runs at site D.
- Ethanol concentrations show the largest increases before completion in
runs A-1, B-1, and C-1.
- Glucose measurements are somewhat problematic and do not change much.
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- Development of Field test kit
- Prediction of fermentation completion using pH.
- Monitoring fermentation quality using alcohol and lactic acid test
strips.
- Detection of excessive microbial activity using temperature.
- Field Studies (next season)
- Validation of the field test kit
- Systematic investigations of factors that influence fermentation
quality, such as the amount of prewashing.
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- Laboratory Research on Fermentation
- Color chart for alcohol test strip
- New strip for lactic acid
- Laboratory Research in conjunction with Professor Vallejos’ laboratory at UCA:
Implementation of screen test for ochratoxin-A, a toxin that is
produced by mold in improperly dried and stored coffee beans. (in progress)
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- Catholic Relief Services-Nicaragua (CRS)
- Asociación para la Diversificación y el Desarrollo Agrícola Comunal
(ADDAC)
- Coffee farmers who hosted our mobil laboratory.
- UCA – Managua Prof. Carlos
Vallejos
- Seattle University/ University of Washington, Bothell
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