“Proceeded of improvement of the quality of the Robusta coffee”.

The present invention relates to a method for improving the quality of the coffee Robusta coffee beans by treating Robusta raw with steam at elevated temperatures and high pressure and then roasting grain into steam.

Robusta coffees are grown in regions of lower altitude. They have a strong and powerful, but also have a flavor note "earthen" and "musty" which is found undesirable in many consuming countries. Because of their taste strong base and their high content of caffeine, Robusta coffees are often mixed with varieties of coffee mild (e.g. the Arabica coffee) largely for enhancing flavor and increase the caffeine content of the final product.

The flavor note "earthen" and "musty" undesirable in many countries consumers can be noticed sensorically even if there is only a small proportion of Robusta coffee in the mixture. The coffee industry attempts therefore long been to find ways to improve the organoleptic Robusta coffee.

A known method of improving the quality of the coffee is presented within the of As-576 515. The method includes exposing the raw coffee beans, with agitation thereof, to steam at a pressure of 1 to 3 atm during at least 1 hour until an amount of water of 6 to 10% is absorbed.

A more recent method of enhancing the quality of green coffee is the object of the ep-to-234 712. The method comprises the following phases:

- treatment of green beans to steam at about 126 to 158 degrees C. at a pressure of about 1.4 to 5.0 bar for a period of about 0.5 to 3.0 min,

- then, moistening of coffee beans to water for a period of 0.5 to 2.0 min,

- novel treatment of coffee beans to steam at a pressure of 1.4 to 5.0 bar for a period of 0.5 to 4.0 min,

- roasting grains.

These methods improve significantly the quality of coffees of different varieties or origins. However, the improvement of Robusta coffee products treated with these known methods is very good. Applicants have a certain flavor note unpleasant night much to their quality.

The present invention therefore aims to provide a specific method for improving the quality of the coffee Robusta.

This is achieved by raising the water content Robusta coffee beans to a level of 30 to 45% and then treating it with saturated steam having a temperature of 140 to 135 degrees C. and a pressure of 3.0 to 4.0 bar for a period of 40 to 120 min, in particular for the removal of the methyl-2 isoborneol, the constituent which is revealed as the compound key responsible for 1' flavor of Robusta.

In the method of the invention, firstly, the water content of crude Robusta coffee beans is significantly increased in relation to the native level, usually about 8 to 12%, so as to reach 30 to 45%. Then, the grains are treated with saturated steam at high pressure. To achieve the purpose of the invention, it is important to abide by the limits of the process parameters, it is to say the range of saturated steam temperature, the pressure interval and duration of treatment indicated.

Optimal results are obtained by treatment with saturated steam at about 138 degrees g and at a pressure of 3.1 to 3.6 bar for a period of 75 to 90 min.

The first phase of the process, raising the grain moisture content Robusta coffee, may be performed in different ways.

In a preferred embodiment of the invention, raw Robusta coffee beans to low water content are steam within a pressure vessel for about 20 min, the steam temperature is raised to about 135 degrees c and the pressure post concomitantly up to about 3.1 bars. It is good that the raw coffee beans are continuously shaken so that water is absorbed also. When the grain moisture content has reached the necessary level (about 30 to 40%), the cock is opened (top) of the pressure vessel and starts the saturated steam treatment provided by the invention. Naturally, raw Robusta coffee beans that have been processed by another method for step-up their water content to 30 to 45% can also be set in a pressure vessel suitable for this treatment with saturated steam. The saturated steam is passed through the grains at a temperature in the small range of 140 degrees to 135 C and preferably to about 138 degrees g and at a pressure of about 3.0 to 4.0 bar and preferably between about 3.1 and 3.6 bars, for a period of about 60 to 120 minutes and preferably about 75 to 90 min. It is good, although this is not absolutely necessary, for agitating the grains during treatment with saturated steam, because this provides more uniform processing.

After this treatment, stopping the flow of steam but is continually removing vapor still present in the pressure vessel for a period of preferably 5 to 10 min of, thereby equalizing the pressure.

Then, the grains are dried to have a moisture content of about 8 to 12% advantage. For this purpose can be used conventional methods of drying. This has the benefit that redrying is not forced to roasting immediately processed grains to steam, but may be to maintain a certain time as unprocessed raw grains with steam. The raw grains processed steam resséchés to have the water content above may be roasted by usual techniques. Preferably, they are roasted in an a fluid bed roaster by introducing, gas roasting hot until they have the desired color index.

The invention provides as another way for the carrying of the water content of ordinary coffee beans at between 30 and 40% by absorbing water at a temperature of 80 to 90 degrees C. for this, raw beans are brought into contact with a quantity of water previously determined experimentally. The raw grains continuously stirred so that water is absorbed completely and also, it is to say that it is not necessary to allow the extraction of water-soluble materials. When the raw grains have absorbed the water amount fixed, it is to say that their water content has reached a level of 30 to 45%, these are treated with saturated steam as indicated above.

The principal the fruit of the invention is that the Robusta coffee products obtained from grain treated in this way have lost their grade "earthen" and "musty". Found they have a pleasant aroma and have substantially more taste of Robusta. As the note of Robusta coffee flavor unpleasant characteristic cannot be removed to a satisfactory degree of any other manner, the invention represents a significant advancement in the field of quality improvement Robusta coffee.

Seen known processes for quality improvement by treating raw grains to steam, which does not eliminate the unpleasant taste characteristic of the Robusta, that performs the method of the invention is quite surprising.

The Robusta coffee which the raw grains have been processed under the conditions of pressure and duration provided by the invention, but at low temperatures, for example less than about 135 degrees C., yet have an "earth" tasting "musty" and, even if an extended processing times.

If processing temperatures are greater than 140 degrees C., an unpleasant taste is still perceivable ("taste processing"), even with shorter periods of treatment, it is to say less than about 60 min. Froze shows that to obtain the surprising improvement of the quality of the coffee lobusta, it is essential and critical to meet specified ranges of temperature, pressure and treatment time and their combination taught by the invention.

Were tests to find the cause of the surprising success of the method of the invention. These have shown that when the operating conditions provided by the invention were exactly met, a certain compound which is probably responsible for the unpleasant flavor note was removed. This compound is methyl-2 isoborneol (exo-L, 2.7, ? - tétraméthylbicyclo 2.2.1 heptanol at above 2).

Methyl 2 isoborneol was identified in coffee by gas chromatography and mass spectrometry. Although this is a known compound, heretofore, it was not known and has not been reported as Robusta coffee component having an influence on 1' flavor thereof.

After identifying this compound by the trials made relatively to the described method and the separated from it, were sensory threshold tests in water have shown that a concentration of about 2.5 to 5.0 ppt of methyl-2 isoborneol in water undergo printing "earthen" and "musty" significant, which means that even extremely small amounts of methyl-2 isoborneol are perceptible sensory and therefore affect the flavor.

The trials with respect to the present invention have finally also confirmed that the methyl-2 isoborneol was still detectable after roasting Robusta coffee products in the non-treated by the method of the invention, meaning that the roasting left alone.

The method of the invention is explained in more detail hereinafter by means of two examples.

Example 1

Is 10 kg of raw coffee Robusta Indonesian in an autoclave of 50 liters. Introduced during 10 minutes in this autoclave steam having a temperature of 115 to 135 degrees C. the pressure in the autoclave rises to 3.1 bars. Continuously stirred seed into the autoclave so that water is absorbed also. After 10 min, the grain moisture content is mounted to 35%.

Then, passed during 90 minutes through the grains of saturated steam having a temperature of 135 degrees C., the pressure in the autoclave being of 3.1 bars. The vapor is passed into the autoclave at 10.2 l/h rate. After 90 minutes of passage of saturated steam, the steam inlet is stopped and removed as 7 minutes the steam still present in the autoclave.

Then, is dried in a fluidized bed dryer Robusta coffee steamed to return its water content to 10% then the trump to an index average color. The sample taste is roasted and compares it to the original. The taste "earth" and "musty" characteristic of the coffee Robusta is practically imperceptible. Those skilled in coffee experience improved of quality relative to the original.

We investigated the methyl-2 isoborneol in the sample roasted with the two-dimensional chroraatographeSichromat Siemens humage analysis. Then 0.6 ppb is found (µg/kg of roast coffee powder) methyl 2 isoborneol in the original, is to do so is found in the sample treated with the method of the invention, the minimum detectable to the analysis being of 0.05 ppb or more.

Example 2

Is 10 kg of raw coffee Robusta Indonesian in an autoclave of 50 liters. 20 To 30 is introduced during this autoclave minutes in, at a rate of about 6.3 l/h, water having a temperature of 80 to 90 degrees g continuously stirred the grains so that water is absorbed also and completely and it does not occur extraction. After introduction of 2.6 kg water for 20 to 30 minutes and complete absorption of the water by the grains, the water content thereof is mounted to about 40%.

Then, saturated vapor is introduced having a temperature of 140 degrees to 135 g when the pressure in the autoclave reaches about 3.1 bars, it opens a valve to the outlet thereof and passed saturated steam through the grains. This operation is conducted in the same manner as in the example 1. As in the example 1, the steam treatment is followed by drying in the fluid bed dryer and the roasting.

The analysis has not ray evidence of raéthyl-to-2 isoborneol roasted in the sample.

The apparatus for implementing the method of the invention can be configured in different ways. The drawing schematically shows a preferred apparatus.

Raw coffee beans are processed in an autoclave 10 having an agitator 11 driven by motor 12. The raw coffee can be loaded into the autoclave 10 and be discharged through a sealable port not shown on the drawing.

In the lower part of the autoclave 10, it is say at its base, is a feed line 13 provided with a solenoid valve 14. A discharge line 15 also having a solenoid valve 16 is connected to the upper part of the autoclave, in the present case to its upper wall. This discharge pipe 15 passes to a conventional condenser 17.

According to the invention, the complete treatment, including pre-processing of the grains for the elevation of their water content, is performed in a single container, namely the autoclave 10. To do this, after having loaded the robust coffee in the autoclave, steam is introduced therein through the feed line 13. At this time, the discharge line 15 is closed. During this steam treatment, coffee beans, in the autoclave, constantly agitated by the agitator 11.

When the moisture content of coffee beans has reached the desired level, is opened the discharge line 15. Maintaining in the autoclave is introduced via the feed line 10 13 saturated steam having a temperature of between 135 and 140 degrees g and a pressure of between 3.0 and 4.0 bars. The treatment lasts about 60 to 120 min. The saturated steam which has passed through the grain will through the exhaust conduit 17 to the condenser 15, where it condenses.

In the first phase of the treatment, may be introduced into the autoclave water instead of steam, also through the feed line 13. In the alternative method of elevating the water content, also stirred the grain with the agitator 11. When the grain moisture content reaches the desired level, the excess possible water can be drained through the feed line 13. Then, the barley grains are treated steaming the manner described above.