Removal of soil and chemical spray contaminants from tomatoes during industrial washing
Abstract
Chemical spray residues on unprocessed tomatoes are known to be above
limits recommended by World Health Organization (WHO) and Food and drug
Act (FDA) at Kenya. Soil contamination on tomatoes delivered for processing
is substantial and water shortages are a problem in tomato processing.
A study was undertaken to investigate the effectiveness of a commercial
tomato washing system on removal of contaminants, water usage and rate of
washing with an aim of Identifying areas of improvement.
samples of tomatoes were analyzed for chemical and soil contaminants
before and after washing through the system. The effect of soil concentration
in the wash water on the effectiveness of the water to remove soil from
tomatoes was also investigated. Water usage and the rate of washing tomatoes
by the system were also determined.
Chemical residues as dithiocarbamates on unwashed tomatoes ranged
from 0.02ppm to 2.00 ppm. Washing reduced the chemicals to between 0.45
and 0.00 ppm. Amounts of chemical residues remaining on washed tomatoes
were negatively correlated to initial chemical concentration on dirty tomatoes.
Amount at soil on dirty tomatoes ranged tram 58.6 ppm to I,115.6 ppm.
Washing reduced the soil to between 9.6 ppm and 191.3 ppm. Amount of soil
removed from tomatoes was negatively correrated to initial amount of soil on
unwashed tomatoes. Soil removed from tomatoes showed an exponential
decrease with increase of soil concentration in the wash water and an
exponential increase with initial soil load on tomatoes.
overall batch washing rate averaged 5.2 ton/h while mean batch
washing rate averaged 11.8 ton/h. Water used for all operations of processing
averaged 5000 litres /ton of tomatoes. with about 66 percent going to the
washing operation.
Analysis of data on water consumption and tomato flow rate through the
system revealed a potential of reducing water usage by at least 400 litres/ton
of tomatoes processed and increase. batch washing rate by at least 7'i if the
system is modified to include water recirculation.
Citation
Njue, M(1996). Removal of soil and chemical spray contaminants from tomatoes during industrial washingSponsorhip
University of NairobiPublisher
Department of Agricultural Engineering, University of Nairobi
Description
Msc-Thesis