03 September 2008

The decaffeination of instant coffee happens before the critical roasting process which will determine the coffee's flavour and aroma characteristics.

There are two modern decaffeination methods, solvent extraction and water extraction.

Solvent Decaffeination

The most commonly used solvents are :
  • Trichloroethylene
  • Methylene chloride
  • Similar chlorinated hydrocarbon.
  • Supercritical carbon dioxide
The method for introducing this moisture does not matter, the most importance is the water content of the bean, and typically between 18% and 55% is sufficient. The moisture is required to soften the cellular structure of the bean.

Basic steps of solvent decaffeination :
  1. Steaming of coffee beans for 30 minutes at 110 °C.
  2. Increase of coffee bean moisture content to <40%.>
  3. Beans flow through extractor columns with solvent at temperatures between 50 °C to 120 °C. Caffeine is removed from beans.
  4. Decaffeinated beans are "steam stripped" of solvent for 90 minutes.
  5. Decaffeinated beans are removed from extractors and dried. Caffeine rich solvent is recycled to be used in step 2.
Water Decaffeination

The advantages are :
  1. Higher extraction rates
  2. Caffeine recovery produces a purer product
  3. Less heat treatment of the coffee bean
  4. No direct solvent contact with the bean

This method takes about 8 hours, considerably longer than solvent decaffeination; however it does seem to produce a better quality end product.
The solid content of the water extract of green beans doubles (from 15% to 30%) as caffeine is taken up. During the 8 hour process about 98% of the caffeine is removed, which is comparable with the solvent extraction method. The decaffeinated beans, now 58% moisture by weight, are washed and dried.

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