Robusta coffee

A process for preparing a substantially non-decaffeinated Robusta coffee having improved aroma and flavor by contacting the roasted coffee with a low molecular weight alcohol for from about 1 to about 20 minutes, and an improved roast and ground coffee and coffee blend made thereby.

BACKGROUND OF THE INVENTION 
This invention relates to the removal of undesirable aroma and flavor 
components from low priced varieties of coffee, primarily the Robustas. 
There are basically two major botanical varieties of coffee, Coffea Arabica 
and Coffea Canephora. The variety Coffea Canephora includes the Robusta 
coffees, whose quality is generally considered to be lower than that of 
the Arabica coffees. The Robusta coffees are grown primarily in Africa, 
Indonesia and Ecuador, and are relatively inexpensive. 
There are a number of Arabica coffee varieties, which are generally divided 
into two major groups, "Brazils" and "Milds". "Milds" are somewhat loosely 
classified as coffees other than Brazils and Robustas. The "Milds" are 
grown primarily in Columbia, Central America and the mountains of East 
Africa and Kenya. They are considered to be premium coffees, and are 
priced accordingly. Two-thirds of the world's commercial coffee beans are 
of the Coffea Arabica variety. 
Robusta coffees generally produce a strong tasting coffee beverage with 
good body, but with peculiar, offensive taste and aroma characteristics, 
which have been described as earthy, bitter, tarry, or rubber-like. 
A major reason for the low cost of the Robusta coffees is their bitterness 
and their unpleasant aroma when brewed. Robustas contain about twice as 
much caffeine as Arabicas, but this is not the sole reason for their 
bitterness. The odor sensation that occurs in the nasal passages when the 
coffee is brewed, smelled, inhaled or ingested is the primary reason for 
rejecting the Robustas as being a "good cup of coffee". For an analysis of 
the flavor characteristics of the Robustas and the "Milds", see the Tea 
and Coffee Trade Journal, 122, 30-36 (1962). 
Robusta coffees are almost never used by themselves as roast and ground 
coffees, but are often blended with Arabicas to provide body and for 
economic reasons. Because of the taste and aroma of the Robusta coffees, 
they generally comprise no more than about 15% to 25% of roast and ground 
coffee blends. Instant coffees typically contain somewhat more Robusta 
than do roast and ground blends. 
It is an object of this invention to improve the flavor of roast and ground 
coffee, especially low grade coffees of the Robusta variety, by removing 
the objectionable tarry, earthy and bitter flavor notes. 
It is also an object of this invention to improve the aroma and flavor of a 
beverage made from roast and ground Robusta coffee beans. 
Still another object of this invention is to produce an economical roast 
and ground coffee blend containing a major portion of Robusta coffee and a 
minor portion of Arabicas, and which has a taste comparable to more 
expensive coffee blends containing a minor portion of Robustas and a major 
portion of Arabicas. 
These and other objects are achieved herein as will be seen from the 
following disclosure. 
SUMMARY OF THE INVENTION 
The present invention encompasses a process for preparing an improved, 
substantially non-decaffeinated Robusta coffee by contacting roasted 
Robusta coffee beans which have been ground or otherwise comminuted with a 
low molecular weight alcohol for from about 1 to about 20 minutes, and 
then removing the alcohol from contact with the coffee. A substantially 
non-decaffeinated Robusta coffee having improved aroma and flavor is 
produced by this process. Robusta coffee treated in the foregoing manner 
can be used alone or in a coffee blend comprising up to about 80% by 
weight of Robusta coffee beans and as low as about 20% by weight of 
Arabica coffees. 
All percentages herein are by weight, unless otherwise specified. 
DETAILED DESCRIPTION OF THE INVENTION 
Low priced coffee, primarily Robusta coffees from Africa and Indonesia, are 
not used extensively in roast and ground coffee or coffee blends because 
they contain objectionable flavors and aromas. This invention provides a 
method for greatly reducing the undesirable aroma impact and flavor 
characteristics of Robusta coffees, thereby making them acceptable for use 
in making beverages. 
In the practice of this invention, low cost coffee beans of the species 
Coffea Canephora, especially Robustas, are roasted in any conventional 
manner. Any standard commercial roasting operation is acceptable for the 
practice of this invention. A steam roasting process such as that 
described by Bolt, et al., U.S. Pat. No. 3,640,726 (1972) incorporated 
herein by reference, which, itself, helps to improve the flavor of Robusta 
coffees, is useful in the practice of this invention. 
In a more conventional and fully acceptable mode, the Robusta coffee beans 
are roasted in standard fashion in a dry atmosphere by exposing the beans 
to air at a temperature ranging from about 300.degree. F. to about 
700.degree. F. for a time period ranging from about 5 minutes to about 20 
minutes. Typical roasting equipment and methods for roasting coffee beans 
which can be employed herein are described, for example, in Sivetz and 
Foote, Coffee Processing Technology, Avi Publishing Company, Conn., 1963, 
Vol. 1, pp. 203-226, the disclosures of which are incorporated herein by 
reference. 
Once the steam roasting or dry roasting of the Robusta coffee beans has 
been carried out, the roasting process is stopped by quenching the hot 
beans with cold water, and/or with liquid nitrogen, or by conveying them 
into a cooling vessel, all in standard fashion. 
The cooled, roasted Robusta beans are then ground to a suitable grind size, 
depending on the end use of the product. A grind size from on 12 mesh U.S. 
Standard Sieve Series to on 60 mesh U.S. Standard Sieve Series can be 
used. Suitable methods and apparatus for grinding coffee beans are 
disclosed in Sivetz and Foote, supra, pages 239-250. 
Most roast and ground coffees are mixtures of different grind sizes. A 
regular grind coffee contains a mixture of from 20%-35% of on 12 and on 16 
mesh, 50%-60% of on 20 and on 30 mesh and 5%-20% through 30 mesh. A 
typical drip grind coffee can contain from 5%-15% of on 12 and on 16 mesh, 
65% to 80% on 20 and on 30 mesh and 15%-30% through 30 mesh. The brewing 
method determines the mixture of grind size. 
To improve the flavor and aroma in the manner of this invention, the roast 
and ground Robusta coffee beans are then contacted with a low molecular 
weight alcohol having from 1 to 3 carbon atoms. Methanol, ethanol, 
1-propanol, 2-propanol and mixtures thereof are all useful in this step. 
Ethanol, 1-propanol and 2-propanol are preferred for this process, but 
ethanol is especially preferred for both organoleptic and toxicological 
considerations. 
Denatured ethanol can be used in the practice of this invention so long as 
the denaturant does not leave a toxic or organoleptically disagreeable 
residue on the coffee beans. Ethanol denatured with methanol is highly 
preferred whereas ethanol denatured with kerosene is not acceptable. 
The butyl alcohols are not particularly useful in this process because of 
their high boiling points and unacceptable organoleptic properties. Benzyl 
alcohol is also not useful herein. 
It is not necessary that the alcohols be anhydrous. One percent water in 
the alcohol does not affect the process and up to 10% water present in the 
alcohol is acceptable. 
The roast and ground Robusta beans can be simply sprayed with the alcohol. 
In more preferred modes, the roast and ground Robusta beans are mixed with 
alcohol, batchwise or in a continuous manner, at a weight ratio of 
coffee:alcohol in the range of from 2:1 to about 1:5. The most preferred 
ratio is about 1 part by weight of roast and ground Robusta beans to about 
1 part by weight of alcohol. 
The alcohol extraction can conveniently be carried out at room temperature, 
or at temperatures of from about 0.degree. F. to 150.degree. F. 
Any conventional extraction apparatus, such as a stirred tank reactor, 
extraction column, mixing vessel, or solvent percolation system, can be 
used. Chemical Engineers' Handbook, Perry, ed. (4th ed., 1963) at pages 
17-2, 19-17 and 19-18 describes leaching apparatus which can be used in 
this process. The extraction is carried out for a shortened period of 
time, from about 1 minute to about 20 minutes. Preferably, the contact 
time between the alcohol and the roast and ground Robusta coffee beans is 
from about 3 to about 5 minutes. 
The very short contact time between the alcohol and the roast and ground 
Robusta coffee does not substantially decaffeinate coffee. Solvent 
extraction to decaffeinate coffee requires a substantially longer contact 
time (usually hours) between the beans and alcohol. 
The alcohol is then separated from the roast and ground coffee beans by 
filtration, centrifugation, or any other conventional means. After the 
excess solvent has been removed, the roast and ground coffee beans are 
then subjected to a drying operation (evaporation) to remove any residual 
alcohol. This drying operation can be carried out by warming the coffee, 
using forced air drying, or drying the coffee beans under vacuum. Indeed, 
any conventional solvent removal process which does not subject the roast 
and ground Robusta coffee to temperatures which would degrade or otherwise 
change their now-optimized odor and flavor characteristics can be used. 
The preferred method of removing the residual alcohol from the moist, 
solvent-treated roast and ground Robusta coffee beans is by vacuum drying 
the ground beans at pressures of from about 0.05 mm to about 300 mm and 
temperatures of from 50.degree. F. to 110.degree. F. 
The alcohol extraction process can be repeated to produce an even more 
bland Robusta coffee. However, repeated extractions do not represent a 
substantial improvement in the overall quality of the product since an 
overly-bland coffee is not desirable. In short, repeated extractions 
remove additional coffee solids without a concomitant improvement in the 
coffee flavor or aroma. 
The alcohol extraction removes undesirable aroma volatiles and some coffee 
solids, which are discarded. For economy, these extracted aroma and flavor 
materials are first removed from the alcohol, which can then be re-used. 
The substantially non-decaffeinated roast and ground Robusta coffee 
prepared by this process can be used in the conventional manner to prepare 
a coffee beverage. Any of the conventional brewing apparatus, e.g., 
percolator, drip coffee maker, and automatic coffee makers, can be used. 
The selection of brewing method determines the size of the grind. The 
resulting beverage has a less bitter, less burnt, and better overall 
flavor and aroma impression than one made with untreated Robusta roast and 
ground coffee. 
In a highly preferred mode, the alcohol-extracted, roast and ground Robusta 
coffee prepared by the above process is blended with the more mild 
varieties of coffee beans, i.e., the Brazilian Arabica beans, Ethopian 
Arabica beans, Columbian "Mild" coffee, or others, to provide a coffee 
product with more balanced flavor and aroma characteristics. 
The Arabica coffee beans used for blending purposes herein are roasted, 
quenched, and ground to from about on 12 mesh U.S. Standard Sieve Series 
to on 100 mesh U.S. Standard Sieve Series, in any conventional manner. The 
roast and ground "Brazils" and/or "Mild" beans are then mixed with the 
roast and ground Robusta coffee beans which have been alcohol-extracted in 
the manner of the present invention. 
Any ratio of alcohol-extracted Robustas to Arabicas can be used herein for 
blend purposes, depending on the flavor desired. To produce a balanced 
flavor which is preferred by most coffee drinkers, a mixture of from about 
15% to about 80% of substantially non-decaffeinated, alcohol-extracted 
roast and ground Robusta coffee beans prepared in the manner of this 
invention and from about 20% to about 85% of the milder flavored beans, 
i.e., the Coffea Arabica varieties is used. For a more balanced flavor, 
the "Milds" and "Brazils" roast and ground beans can also be mixed. Thus, 
blends can contain Central American "Mild", Brazilian and Ethopian Arabica 
beans, along with some Columbian "Mild" coffees. The amount of the milder 
coffee components and the number of these components which are blended 
will depend upon the particular taste or flavor desired in the final 
product. 
The blends can also be improved by using a finer grind of the Arabica 
coffees and a somewhat coarser grind of the alcohol-extracted Robusta 
coffee prepared in the manner of this invention. The size of the grind 
will depend upon the method of beverage preparation, as noted above, as 
well as the aroma and flavor impact desired in the final product. 
Highly preferred roast and ground coffee blends which are flavorful, 
aromatic and economical contain about 60% to 80% of the substantially 
non-decaffeinated improved Robusta roast and ground coffee prepared by 
this invention. 
In another aspect of this invention, "culls" can be improved in aroma and 
flavor by this process. "Culls" are inferior coffee beans, either of the 
Arabica or Robusta variety which are rejected during processing because of 
their physical or organoleptic properties, i.e., appearance, aroma or 
flavor. 
The "culls" are roasted using standard roasting procedures. They are then 
ground to a suitable grind size, depending upon the end use of the 
product. To improve the flavor and aroma in the manner of this invention, 
the roast and ground "culls" are then contacted with a low molecular 
weight alcohol having from 1 to 3 carbon atoms in the same manner that the 
roast and ground Robusta coffee beans are treated. 
The very short contact time between the alcohol and the roast and ground 
"culls", from about 1 to about 20 minutes, does not substantially 
decaffeinate these coffee beans. 
The aroma and the flavor of the "culls" is greatly improved, and they are 
then suitable for preparing a roast and ground coffee blend which is both 
flavorful and aromatic. 
The following examples illustrate the practice of this invention but are 
not intended to be limiting thereof.

EXAMPLE I 
50 Grams of roast and ground African Robusta coffee were roasted to a 
"standard" roast, quenched with liquid nitrogen, and cold ground to a 
"regular" grind. This roast and ground coffee was mixed with 50 grams of 
100% ethanol. The mixture was agitated for about 3 to about 5 minutes, and 
the excess ethanol was removed by filtration. The ethanol-moist coffee 
grounds were then placed under a vacuum of 1 to 10 mm mercury at 
100.degree.-105.degree. F. temperature to remove any residual ethanol. The 
resulting roast and ground Robusta coffee was not substantially 
decaffeinated. 
Robusta coffee treated in the foregoing manner is characterized by a 
greatly reduced level of objectionable "tarry" notes in its aroma, and, 
when brewed, the resulting coffee beverage has an improved flavor. 
When Indonesian Robusta coffee beans are used in the above process, a roast 
and ground coffee with improved aroma and flavor is produced. 
The beverage prepared by brewing the roast and ground Robusta coffee 
prepared in the manner of Example I has a less bitter and less burnt taste 
than coffee brewed from untreated, roast and ground Robusta coffee beans. 
When the ethanol is replaced by 2-propanol, or 1-propanol, similar results 
are obtained. 
When ethanol which has been denatured with about 5% methanol is used to 
replace the ethanol, similar results are obtained. 
Twenty roast and ground coffee drinkers were asked to compare the coffee 
beverage made from the untreated Robusta coffee beans with ethanol 
extracted Robusta coffee beans in a paired comparison blind test. Table 1 
summarizes the results. The numbers are the average grades based on a nine 
point scale. A higher number indicates more of the quality being 
described. 
TABLE 1 
______________________________________ 
Alcohol 
Untreated 
Treated Difference 
______________________________________ 
Color 6.35 6.20 -0.15 
Strength 5.75 5.95 +0.20 
Burnt flavor 5.60 5.25 -0.35 
Acid flavor 5.50 4.55 -0.95 
Bitter flavor 
5.80 5.10 -0.70 
Off-Flavor 6.35 5.40 -0.95 
Overall impression 
2.20 2.90 +0.70 
______________________________________ 
These results indicate that the alcohol treated coffee is significantly 
better than the untreated coffee in acid flavor, bitter flavor, off-flavor 
and overall impression. 
EXAMPLE II 
A roast and ground coffee blend was prepared by mixing 80% alcohol 
extracted African Robusta coffee beans prepared in the manner of Example 
I, herein, with 20% of a mixture of Brazilian Arabica and Columbian Mild 
coffees. 
When the coffee blend of Example II is used to prepare a coffee beverage, 
the flavor and aroma is similar to a roast and ground coffee blend 
containing 20% Robusta coffee beans and 80% mild and Arabica coffees, at a 
substantial cost savings. 
EXAMPLE III 
50 Grams of coffee beans which were "culled" as being inferior were roasted 
to a "standard" roast, quenched with liquid nitrogen, and cold ground to a 
"regular" grind. This roast and ground coffee was mixed with 50 grams of 
100% ethanol. The mixture was agitated for about 3 to about 5 minutes and 
the excess ethanol was removed by filtration. The ethanol-moist coffee 
grounds were then placed under vacuum of from 1 to 10 mm/mercury at 
100.degree.-105.degree. F. temperature to remove any residual ethanol. The 
resulting roast and ground coffee was not substantially decaffeinated. 
The coffee "culls" treated in the foregoing manner are characterized by a 
greatly reduced level of objectionable aroma, and when brewed, the 
resulting coffee beverage has an improved flavor. 
When ethanol which has been denatured with about 5% methanol is used to 
replace the ethanol of Example III, similar results are obtained.