Studies on the Pungent Constituents in Black Pepper (Piper nigrum L.)

Part IV. Pungency of piperine

Abstract

Pungency of black pepper is due to piperine and its cis-isomers give almost no heat. Threshold level of pungency of piperine is 5 to 10ppm which is almost the same level of its solubility in water (6.2μg/ml).
Crystalline piperine which is easily crystallized shows almost no pungency, while piperine, which is dissolved or dispersed minutely in water so much as to give enough stimulus to the nervous cells on tongue, has strong heat. For example its alcoholic solution gives very strong heat immediately after poured into water and loses its pungency after crystallization.
By model experiments (such as piperine in solution, in starch paste, in the presence of edible oils, adsorbed on filter paper and so on) it was observed how different states of piperine showed different degrees of pungency.
It was assumed that loss of pungency of ground pepper during storage is due to the gradual crystallization of piperine which had been dissolved in essential oils or oily by-alkaloids in pepper, although it has been attributed to gradual isomerization of chavicine into piperine by NEWMAN or piperine into isochavicine by CLEYN.