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NATIONAL CONFERENCE : ROLE AND CHALLENGES
CHEMISTRY OF COFFEE ROASTING & AROMA
FORMATION
Presented by :
Anil Kumar Saini1, Aman Paul1, Sajan Palanchoke1, Sachin
Kumar Verma2
1M.Tech. Food Tech., Department of Food Process
Engineering, VSAET, SHIATS, Allahabad
2M.Sc. Dairy Technology, Department of Dairy Technology,
WSFDT, SHIATS, Allahabad
Presented by :
Anil Kumar Saini1, Aman Paul1, Sajan Palanchoke1, Sachin
Kumar Verma2
1M.Tech. Food Tech., Department of Food Process
Engineering, VSAET, SHIATS, Allahabad
2M.Sc. Dairy Technology, Department of Dairy Technology,
WSFDT, SHIATS, Allahabad
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INTRODUCTION
Coffee is brewed beverage with a dark, acidic flavor
prepared from the roasted seeds of the coffee plant, colloquially called
coffee beans. The beans are found in coffee cherries. Green coffee is one of
the most traded agricultural commodities in the world.
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Mesocarp
Spermorderm
Endocarp
Mucilaginous
PRO
CESS
ING
OF
GRE
EN
COF
FEE
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ChangesDuring
Roasting
Increased
in vol.(50-80%)
Green toBrowncolor
Weight
loss(13-20%)
Typicalroasterflavor ofbeans
Sp. Gravity
1.126-1.272 to
0.570-0.694
Horny,tough anddifficult to
crack beansbecome
brittle andmellow
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Composition of green and roasted coffees (according to variety) and of instant
coffee (expressed as a percentage of the dry basis)
Component Arabica
Green Roasted
Robusta
Green Roasted
Instant
Minerals 3.0-4.2 3.5-4.5 4.0-4.5 4.6 5.0 9-10
Caffeine 0.9-1.2 appox 1.0 1.6-2.4 appx2.0 4.5-5.1
Trigonelline 1.0-1.2 0.5-1.0 0.6-0 .75 0.3-0.6 -
Lipids 12-18 14.5-20 9.0-13.0 11.0-16.0 1.5-1.6
Total Chlorogenic
acids
5.5-8.0 1.2-2.3 7.0-10.0 3.9-4.6 5.2- 7.4
Aliphatic acids 1.5-2.0 1.0-1.5 1.5-2.0 1.0-1.5 -
Oligosaccharides 6.0-8.0 0-3.5 5.0-7.0 0- 3.5 0.7-5.2
Total Polysaccharides 50-55 24-39 37-47 - appx 6.5
Amino acids 2.0 0 2.0 0 0
Proteins 11.0-1.03 13.0-15.0 11.0-13.0 13.0-15.0 16.0-21.0
Humic acids - 16.0-17.0 - 16.0-17.0 15.0
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Protein denatured(500C).
Water evaporates.
Browning(1000C) due topyrolysis of organiccompound accompanied byswelling & an initial drydistillation.
Drying
ROASTING PHASES:
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Development
Release of volatile products at 1500C(H2O, CO CO2), results in increasein bean vol.
Some of the CO2 is absorbed within the texture of the roasted beans.
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Decomposition
At 150-2000C the beans being forced to popand burst along the groove.
Formation of bluish smoke and the release ofcoffee aroma.
Flavor produces
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Fullroasting
The moisture contents of beans drops to the level of 1.5-3.5%.
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Protein
Acid hydrolysatesby
30%
CHANGES IN PROTEINS:
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Sucrose &monosaccharid
e
Degraded&
Decompo
sed
Caramlizationof Sugars
CHANGES IN
CARBOHYDRATES:
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Diterpenes, Cafestol,
& Kahwoel
Degradedby roasting
Diterpene glycosides
CHANGES IN LIPIDS:
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Trigonelline(0.6%)decompos
ed upto50 %
Nicotinicacid
PyridineMethylEsters
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Volatile
acids,
Acetic
Acid
Formic
Acid
CHANGES IN ACIDS:
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Non-volatileacids
CitricAcid
Pyruvic
Acid
TartaricAcid
Lactic
Acid
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Chloroge
nic Acid
Decomposed70% by
strongerroasting
Decompos
ed 30% byroasting
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Malic acid
MesaconicAcidFumericAcid
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CitricAcid
ItaconicAcid
Mesacon
ic AcidCitaconic Acid
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CaffeineChlorpgenic
acid
Caffeine in addition to stimulation also contributes to the bitterness of the coffee.
(1:1)
CHANGES IN
CAFFEINE:
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Melanoids
MaillardReaction(carbohydratecaramelization)
Bitter flavor
Thermolysis of mixture ofcarbohydrate and protein.
MAILLARD REACTION:
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Pyrolysisofsucrose& othersugars
Pyrroles
Thiazoles &
Oxazoles
Thiophenes
Pyrazines
CHANGES IN OTHER CONSTITUES:
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Thermaldecomposition
of chlorogenicacids
Phenols
Carbonyl
esters
Polycycliccompoun
ds
Phenols
esters
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Carbohydratefragmentation
Alcohols
Carbonylcompounds
Alicycliccompounds
Hydrocarbons
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Light roastedUnroasted beanMedium & dark
roasted
Antioxidantactivity & totalPhenoliccontent
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Roasting condition
28 are odour volatilearomatic compoundscontribute strongly to thecoffee flavour .
Phenolic acidconcentration inroasted coffee
fresh note of coffeearoma, ( rapidly lost, &are considerable
indicators of freshness).
Methane, thioland 2, 3-
pentanedione
AROMA FORMATION:
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The results indicated that roasting degree significantly influenced the
colour, volatile compound, phenolic composition & antioxidant activity
of the coffee beans.
It is interesting to note that some phenolic acids increased while some
decreased in Catimor coffee beans after roasting, suggesting that heattreatment influenced both positively and negatively.
Therefore, it is extremely important to prepare coffee in a way that the
coffee has low enough level of phenolic acid to prevent acid reflux yet a
sufficient amount for antioxidant activities.
CONCLUSION
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