Colorimetric Method of Determination of Pungent Constituents of Pepper
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Date
1970
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Abstract
Pipeline is an important predominating pungent constituent in pepper. Pepper also contains small quantities of chavicine and piperettine which possess sharp biting and pungency. A survey of the existing methods showed that the ultraviolet spectrophotometric method which is widely used is specific for piperine only and not for the other pungent constituents. In the method described here, it is possible to determine the total pungency due to piperine, chavicine and piperettine. The method consists of hydrolyzing the piperidine containing pungent constituents to liberate piperidine which is reacted with carbon disulphide to form piperidinium pentamethylene dithiocarbamate. Piperidinium pentamethylene dithiocarba-mate reacts with copper sulphate to give a yellow colour which has an absorption maximum at 435m/*. One mole of piperine on hydrolysis gives one mole of piperidine. The cupric complex obeys Beer's law between a concentration of 1 to 14/ig/ml of piperidine. The method is applicable to determine the trace quantities of the total pungent constituents present in pepper and also in the oleoresin of pepper. Pepper is one of the most important of spices used for both flavour and aroma. Piperine is known to be the predominating constituent responsible for the sharp biting and pungency. The quality of the pepper and also of the oleoresin of pepper is dependent on the amount of piperine present in them. The value of pepper is, therefore, dependent on its piperine content. Hence, methods for the estimation of piperine are becoming more important. Recently, Graham1 and Labruyere2 have reviewed the available methods and pointed out their merits and demerits. Among the various methods the spectrophotometric method3' "' 5 is very specific for piperine and reliable under controlled conditions. However, it is known that there are other constituents such as chavicine6 and piperettine' which are also responsible for the pungency. The spectrophotometric method fails to measure the presence of these and it has been found that in dilute solutions the piperine which has trans-trans configuration slowly transforms to its isomeric form chavicine8 (cis-cis configuration). The present method is based on the alkaline hydrolysis of piperidine containing compounds to liberate quantitative piperidine2. The piperidine is reacted with carbondisulphide to get piperidinium pentamethylenedithiocarbamate" which gives a yellow colour with a copper salt forming copper piperidine pentamethylene dithiocarbamate10. The various above reactions using a typical example, piperine are represented below: The yellow colour of the complex has an absorption maximum at 435m/<. In fact, the dialkyldithiocarbamates11 are an important group of reagents for the detection and determination of traces of copper.
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Reprinted from The Flavour Industry, 1, 173-135 (1970)