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Decaf-environmental problems.

Decaf-environmental problems

Economic evaluation of various processes for decaffeination of coffee indicate that the original standard method of using a chemical solvent still yields the highest quality from a flavor standpoint and is the most reasonable in cost. But many environmentalists have expressed concern about this procedure because of fears of atmospheric pollution by solvent losses during extraction. The type of chemical solvent used - methylene chloride is popularly believed to be detrimental to the ozone layer which is alleged to filter out cancer causing light rays from sunlight.

Since the introduction of Sanka (from the French "sans caffeine") early in this century, many solvents have been explored for their caffeine extraction qualities. The family of chlorinated hydrocarbons have been preferred for their high extraction efficiency, excellent separation from water-wet beans, ease of recovery and recycling, low cost and lack of flavor effect. This family includes chloroform, carbon tetrachloride, trichlor-ethylene and many others. With recent emphasis on safety and reduced pollution, methylene chloride, also known as dichlor-methane and [CH.sub.2][C1.sub.2] has become the solvent of choice, having the lowest toxicity and general balance of favorable properties.

Reservations about toxicity of residue from this solvent have been largely resolved. After coffee extraction by this chemical, steaming and drying of the wet, green, extracted beans evaporate essentially all of the solvent since it boils at 104 [degrees] F; and is carried off by the steam which is at least 212 [degrees] F. Any residual amounts of solvent not vaporized by this steam are banished by the much higher roasting temperature of some 400 [degrees] F. The F.D.A. has established ten parts per million of [CH.sub.2][C1.sub.2] as a safe level in decaffeinated coffee. Repeated analyses has seldom exhibited over one-tenth this level or one ppm. Thus, the public has been assured that there is no health hazard from any chemical residue in the cup of coffee decaffeinated by this procedure.

Field reports on the flavor quality of green coffee decaffeinated by various procedures indicate that the chlorinated solvent produces the highest flavor green, the water process the lowest quality; with carbon dioxide-supercritical method and ethyl acetate, somewhere in between.

In all decaffeination procedures, the green coffee is initially steamed so that the beans swell and become completely water- saturated. The native caffeine and other water soluble components dissolve in this moisture. [CH.sub.2] [C1.sub.2], as one of the best caffeine solvents, extracts this active principal from the water phase and little else. Thus after extraction, when the green beans are dried, they are practically identical with the original coffee, absent most of the caffeine.

The water process (sometimes referred to as the Swiss water process) is the ideal method for decaffeination from the standpoint of the use of no foreign solvent, no strange residue, no toxicity hazard, no fire precautions, no atmospheric pollution. In this procedure, the green beans are again steamed to swell and saturate them. They are then completely extracted with water.

The aqueous extract is percolated over activated carbon, which adsorbs most of the caffeine. The decaffeinated liquor is then added back to the extracted green beans which are then dried and roasted.

Although the type of activated carbon is specifically selected for its affinity for caffeine, it may also extract other components from the liquor, particularly some of the precursors of coffee aroma and flavor. Accordingly, when roasted, beans decaffeinated by this procedure would not be as identical as the unextracted beans and would not achieve the quality of the original crop. They could be quite inferior in flavor to the same beans processed with a chlorinated solvent.

The same situation may hold for other extraction procedures. Ethyl acetate, an edible solvent used for decaffeination, is a highly polar solvent, which means it has more of an affinity for other water soluble components than chlorinated or non-polar solvents. It too may extract some flavor precursors from green coffee, but it would be to a lesser extent than water. Super-critical carbon dioxide, the natural solvent, may also be responsible for a slight reduction in aroma. This could be rectified by separating the caffeine from any other components that may be removed during this operation, and adding back these residual components, but it does complicate the procedure.

From an equipment standpoint, the [CO.sub.2] process is the most expensive of all. Operating at very high pressure, it requires heavy steel tanks, pumps and lines strong enough to contain pressures of over 1,000 pounds per square inch (over 75 times atmospheric-pressure). In addition, although [CO.sub.2] is a normal component of the air we breathe and exhale in a confined room, 10% concentration will cause unconsciousness in humans. Above that it can be as fatal as carbon monoxide.

We can now examine the accusation, described by one reader that "During decaffeination with this chemical solvent at the processing plant, harmful chemicals are emitted into the O-Zone."

No Previous Attempts

During the first half of this century, when chlorinated solvents were the exclusive agents used for decaffeination, no attempt was made to prevent the small natural solvent losses that occur in a process of this type. It was less expensive to add make-up solvent than to install high priced solvent recovery equipment. But the total-decaffeination market was so small that it contributed an infinitesimal fraction of the quantity of solvent released to the atmosphere by major polluters, like the dry cleaning industry, industrial metal cleaning, painting and even the automobile. Even today these industries lose more solvent in one day than the total amount used in a year of decaffeination. In fact, to meet the new environmental regulations which now carry severe penalties, users of chemical solvents are installing solvent recovery equipment so that their release of these vapors are well below currently established regulations.

The solvent recovery equipment consists of passing all plant affluent containing solvent fumes through a fixed bed of adsorbent granules having an affinity for chlorinated hydrocarbons. This continues until the bed becomes saturated. At this point, solvent gas begins to be emitted and is automatically detected by a sensitive instrument. The detector then automatically switches the effluent stream immediately to a parallel bed of fresh adsorbent. The first batch of granules is then relieved of its burden by steaming, and the solvent is condensed and recovered for re-sue. When the second bed is saturated, the stream is switched back to the revived first bed, and the second bed is similarly renewed. The cycles can be repeated hundreds of times without appreciable atmospheric contamination.

The coffee industry has come a long way since large scale roasting and open venting perfumed the atmosphere of sections of Front Street, Brooklyn, Hoboken and others. Roasters have learned that it is better to join the E.P.A. in its battle for a better atmosphere than to flght it. The industry has also found that solvent recovery makes good economic sense as well as good environmental policy. Consumers of coffee decaffeinated by chemical solvents need have no fears of either residues in the cup or clean air contamination from this solvent.
COPYRIGHT 1991 Lockwood Trade Journal Co., Inc.
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Copyright 1991 Gale, Cengage Learning. All rights reserved.

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Title Annotation:environmental problems with decaffeinated coffee processing
Author:Lee, Samuel
Publication:Tea & Coffee Trade Journal
Article Type:column
Date:Jul 1, 1991
Words:1194
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