Change of pyrethrin content during drying of pyrethrum flowers
Abstract
Pyrethrum is one of the major cash crops in
Kenya. To extract the insecticidal constituents found
in the pyrethrum flower, the flower has to be dried.
High temperature drying may result in pyrethrin loss .
.This work looks at pyrethrin loss trends as a function
of temperature with the aim of generating information
that may be used to reduce the loss.
The flowers were dried from an initial
moisture content of 80 to 84% (wet basis) at
temperatures of 70 to 175°C. Drying was done in a
thermostatically controlled forced air oven while the
pyrethrin content for various lengths of drying was
measured using photo-spectrometric method. The rate of
moisture removal and change in pyrethrin content was
determined.
It was observed that like any other crop
pyrethrum loses moisture exponentially at a constant
drying temperature. However I a unique pattern of
pyrethrin loss with time during drying was observed.
There exists a period during which there is no loss of
pyrethrin.
The results show that a Newtonian equation
can be used to depict the moisture loss. Two
expressions for predicting pyrethrin loss were
developed and both show good agreement with
experimental Data. An equation for predicting when the
no-loss duration end after the beginning of drying for
the temperature range of 70 to 175°C is also given.
The equation which depicts the no-loss
duration and the expression for moisture removal can be
used to set time-temperature schedules which will
ensure minimum loss of pyrethrin during drying.
Citation
Mwithiga, G.(1990). Change of pyrethrin content during drying of pyrethrum flowersSponsorhip
University of NairobiPublisher
Department of Agricultural Engineering, University of Nairobi,
Description
Msc-Thesis