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Pale yellow

1. Beta-pinene 2. Para-cymene 3. Gamma-pinene 4. Thymol

* Commercial sample obtained from Synthite Chemicals Ltd., India. Note: Odour of oleoresin and volatile oil obtained by supercritical extraction was like that of fresh crushed seed.

1. Beta-pinene 2. Para-cymene 3. Gamma-pinene 4. Thymol

* Commercial sample obtained from Synthite Chemicals Ltd., India. Note: Odour of oleoresin and volatile oil obtained by supercritical extraction was like that of fresh crushed seed.

4.4.5. Hops extraction

The use of hops extract in the production of beer has increased to the point that almost 25% of the world's supply of hops is converted to hops extract.

The desirable constituents of hops are the soft resins which contain an alpha-acids fraction (mixture of several humulones). In the brewing process, the alpha-acids are isomerised to give beer its characteristic bitter taste. Thus, in the production of hops extract, it is necessary that the extraction conditions favour the extraction of the soft resins with minimal production of undesirable by-products. The process conditions used with supercritical carbon dioxide are in the temperature range of 35-80°C and pressure range of 80-300 bar. This gives an olive-green, pasty extract with an intense aroma of hops. The extent of extraction of alpha-acids is almost 99% and is above the required minimum of 95%. The extract is superior to the ones obtained by using either methylene dichloride or n-hexane as solvent.

The hops extraction may also be carried out by using liquid carbon dioxide at lower temperatures and pressures of 50-70 bar. The hard resins can be eliminated from the extract in this way.

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