by Michael Boyd
A STUBBORNLY glutinous bottle of tomato ketchup inspired Ted Hill to an invention that has revolutionised the on-site counting of
bacteria. It has become one of the biggest forces in the continuing
struggle against the potentially lethal microbial contamination of
While shaking the bottle over his breakfast plate, Hill idly wondered
if he could substitute the thixotropic gelling agent in the sauce for
the traditional agar gel that has been used by researchers to grow
microbial colonies for over 100 years.
The problem he wanted to overcome was that testing for infestation
was a costly and time-consuming business because it needed a
laboratory where heat could be applied to melt the agar before the
introduction of the microbes.
He was right in his early morning ruminations. After exhaustive tests
his company, Echa Microbiology Ltd of Cardiff, Wales, has come up
with a new nutritive solution gelled with thixotropic and/or pseudo
plastic agents in place of agar. It is called Echa Smartgel.
"An aqueous or non-aqueous sample can be dispersed in the gel by
simply shaking it in the hand and then allowing the gel to reset as a
flat horizontal layer," says Ted Hill. "During incubation, colonies
develop comparable to their normal formation in traditional plates."
A sensitive redox indicator gives an early indication of colony
growth and helps with counting the number of bacteria present. The
accuracy is equal to that of a traditional agar plate count. Very
large numbers of microbes produce a coloured formazan within a few
hours - a real time test.
Until this inspired moment the traditional count technology had been
confined to laboratories because the 1.5 per cent aqueous solution of
agar used in petri dishes required a temperature of 85 degrees
Celsius (C) to melt it and set again at 39 degrees C. Such
temperatures precluded their use for on-site counting of bacteria in
distillate fuels such as aviation kerosine or diesel derv.
There have been growing practical problems for the air transport
industry associated with microbial contamination. During the last few
years, changes in fuel composition and handling have resulted in some
changes in the type of causative micro-organisms and to a large
increase in their distribution and occurrence.
Filter blockage, coalescer malfunctions, injector fouling,
accelerated corrosion, fuel gauge errors and water entrainment are
but some of the more common consequences of contamination. The
results, if unchecked, could be catastrophic for an aircraft and
The blame for tolerating or even encouraging microbial proliferation
has often been laid at the end-user and his fuel supplier; "poor
housekeeping" is normally cited as the prime cause, particularly
failure to remove free water. But the problem also occurs in storage
and distribution systems.
Whole cargoes have been affected necessitating expensive and
time-consuming procedures to decontaminate the fuel. These
developments have highlighted the need for improved standards of fuel
system management and contaminant detection. But now, with the
production of the ketchup-inspired Echa Smartgel, checks can not only
be done in situ but quickly and cheaply.
"Preliminary tests on water, milk and various emulsions suggest that
the methodology will have wide applications both in the laboratory
and on site," added Mr Hill. "It is also going to be a boon for small
medical and cosmetic companies that do not have a microbiology
laboratory, and has great export potential for testing drinking water
in developing countries."
Already the new Smartgel is being field tested all over Europe by
international oil companies and airlines.
Echa is not only involved in monitoring bacterial contamination but
is also very much concerned with its elimination, not only from
distillate fuels but in any bulk liquid storage.