Decaffeination of tea and coffee

Decaffeination of Coffee and Tea This application is driven by the environmental acceptability and nontoxicity of CO2 as well as by the ability to tailor the extraction with the adjustable solvent strength. It has been practiced industrially for more than two decades. Caffeine may be extracted from green coffee beans, and the aroma is developed later by roasting. Various methods have been proposed for recovery of the caffeine, including washing with water and adsorption. 

A recent development in liquid-liquid extraction has been the use of supercritical fluids as the extraction-solvent. Carbon dioxide at high pressure is the most commonly used fluid. It is used in processes for the decaffeination of coffee and tea. The solvent can be recovered from the extract solution as a gas, by reducing the pressure. Super critical extraction processes are discussed by Humphrey and Keller (1997). 

Extraction processes for natural products including the decaffeination of coffee and tea and the isolation of nutraceuticals, flavors, and fragrances... 

Lack A and Seidlitz H. 1993. Commercial scale decaffeination of coffee and tea using supercritical CCb. In King MB and Bott TR, editors. Extraction of natural products using near-critical solvents. Glasgow Blackie Academic, p. 101—139. 

A further method separates the extracted substances by absorption. Basic for this method is that there should be a high solubility of extracted substances in the absorption material, and that the solubility of absorption substance in the circulation solvent should be as low as possible. Further, the absorption material must not influence the extract in a negative way and a simple separation of extract and absorption material has to be available. An ideal absorption material is therefore a substance which is present in the raw material. Most plant-materials contain water, which can act as a very successful absorption material. An ideal example is the separation of caffeine for the decaffeination of coffee and tea. On the one hand, water has a low solubility in CO2, and on the other, water-saturated CO2 is necessary for the process. The extracted caffeine is dissolved into water in the separator and caffeine can be produced from this water-caffeine mixture by crystallization. One advantage of this separation method is that the whole process runs under nearly isobaric conditions. 

An industrial-scale application is the decaffeination of coffee and tea where a direct separation of the extracted caffeine in the extractor is realized. A layer of activated carbon follows a layer of raw material, and so on. In this way, the loaded extraction fluid is directly regenerated in the adsorption layer and enters as pure solvent into the next stage of raw material. The great advantage of this method is that no further high-pressure vessel is necessary for separation, which reduces investment costs dramatically. 

As one can see from Table 6.6-2 the decaffeination of coffee and tea is the largest application for supercritical fluid extraction, in terms of annual capacities and investment costs. Since the beginning of the 1970s, to the early 1990s, nearly 50% of the whole production capacity for decaffeination of coffee and tea changed to the supercritical extraction process. As the market for decaffeinated coffee is stable, no further plants have been installed within the past eight years. 

E Lack and H Seidlitz, Commercial scale decaffeination of coffee and tea using supercritical COr In Extraction of Natural Products using Near-critical Solvents MB King and TR Bott, Ed., Chapman Hall, London, UK, 1993, pp 101-139. 

Supercritical fluids (scf) are highly compressed liquids or gases. The latter already have an established role in "clean extraction (substitution of chlorinated/organic solvents) on an industrial scale (e. g. decaffeination of coffee and tea, extraction of hops, spices, etc.). The specific physical and chemical properties of scf make them particularly suitable for a variety of other applications, e. g. reactions, powder technology and impregnation. 

Based on its ability to enhance solvating power by increasing fluid density, supercritical fluid extraction offers an attractive alternative for fractionation of fats and oils. It works by the phenomena of selective distillation and simultaneous extraction, as has been shown by many researchers [3-5]. While the use of supercritical fluids in the extraction of numerous biomaterials has been reported, its commercialization has been limited to the decaffeination of coffee and tea and to the extraction of flavors from hops and spices. The chemical complexity of most food ingredients and their tendency to react and degrade at elevated temperatures, emphasize the difficulties of supercritical solvent selection. Carbon dioxide is the preferred supercritical solvent (its properties have previously been cited [6]). 

From our experience in the decaffeination of coffee and tea and the extraction of oils and other valuable ingredients from natural materials it has been deducted that pressures between 250 and 400 bars will be suitable for the extraction of the nibs. Because of the limiting design pressure of larger production plants for all tests the extraction pressure was fixed to 300 bars. 

Plants and plant extracts have been used as medicine, culinary spice, dye and general cosmetic since ancient times. Plant extracts are seen as a way of meeting the demanding requirements of the modem industry. In the past two decades, much attention has been directed to the use of near critical and supercritical carbon dioxide solvent, particularly in the food pharmaceutical and perfume industries. CO2 is an ideal solvent because it is non-toxic, non-explosive, readily available and easily removed from the extracted products. At present the major industrial-scale applications of supercritical fluid extraction (SFE) are hop extraction, decaffeination of coffee and tea, and isolation of flavours, fragrances and other components from spices, herbs and medicinal plants [1-4]. 

As reported in a lot of reviews, extractions with supercritical solvents have a very promising commercial potential. Until now the commercialization is mainly restricted to batchwise extraction of solids with carbon dioxide (e g. decaffeination of coffee and tea, extraction of hop). Laboratory experiments and operation of small-scale pilot plants gave favourable economic values for continuous extraction of liquids with C02 and other gases. Only a few extractions with C02 or C HS are performed already on a small industrial scale. For research purposes and product development a new high pressure counter-current extraction plant was erected. To get greater amounts of product the explosionproof plant was constructed in pilot scale using a special modular concept and an effective visual control system. 

Ethyl acetate is used primarily as (1) a coatings solvent for paints, lacquers, and varnishes (2) an extraction solvent for various processes, including decaffeination of coffee and tea (3) a process solvent in the pharmaceutical industry and (4) a carrier solvent for printing inks, adhesives, and nail polish. It is also used in the manufacture of artificial leather and perfumes, and in certain household products including airplane glue, and paint and nail polish removers. 

Some of the areas in which supercritical CO2 (SCCO2) is commercially important are summarized in Figure 8.9. Extraction processes in the food, tobacco (nicotine extraction) and pharmaceutical industries dominate. Supercritical CO2 is a selective extracting agent for caffeine, and its use in the decaffeination of coffee and tea was the first commercial application of a supercritical fluid, followed by the extraction of hops in the brewing industry. Solvent extractions can be carried out by batch processes, or by a continuous process in which the CO2 is recycled as shown schematically below ... 

The application of supercritical fluids, for example SCCO2, as an environmentally acceptable replacement for conventional solvents, is well documented in the industry. Based on the work of Zosel, the decaffeination of coffee and tea using SCCO2 was the first industrial use of this technology [1]. The advantages of supercritical fluids are not only useful in separation techniques, for example supercritical fluid extraction (SFE) or supercritical chromatography (SFC), their application as process solvents is well recognized [2, 3]. 

Extraction of steroids [28] removal or replacement of liquid solvents (e.g., chlorinated solvents) [3] Production of aerogels [13-26] dyeing [29] Decaffeination of coffee and tea [30,31] extraction of bitter hop fractions extraction of fragrance and flavoring components extraction and fractionation of fatty acids (e.g., omega-3) recovery of vitamin E from processed soya oil [4] production of sesame-based antioxidants [32] and sterilization and microorganism inactivation [33,34]... 

Commercial scale decaffeination of coffee and tea using supercritical CO2... 

Methylene chloride is used as an extractant in the recovery and purification of a wide variety of materials including oils, fats, and waxes. The chemical is used for the decaffeination of coffee and tea, oleoresin extraction from a variety of spices, and for the extraction of hops. As with tablet coatings, little or none of the chemical remains in the finished product. 

Extraction using supercritical carbon dioxide has been an established industrial-scale technique for many years. High-pressure CO2 extraction is already widely used, for example, for dealcoholization decaffeination of coffee and tea processing of tobacco, hops, spices, and fats and oils from both vegetable and animal sources and also to extract specific compounds or active ingredients for the food, beverage, and tobacco sector and in the chemical and pharmaceutical industries, as well as in the fields of cosmetics, leafher, textile, paints, and beverages. 

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