Discussion
Microbial dry weight is a standard biomass parameter in
research and production settings. The traditional method
for its determination using ovens is time consuming and
tedious, requiring equilibration between drying and
weighing. Some studies have investigated more efficient
drying methods, such as the use of microwaves (Buono
and Erickson 1985), but a more significant advance has
been made by using moisture analysers that combine drying
and on-line weighing. Kennedy and Phillips (1996)
and Fenton and Kennedy (1998) used a moisture analyser
for biomass determination of fermentation samples and
fruit pomace, but the balance used had a low accuracy
requiring large sample volumes. Modern moisture analysers
with rapid infrared-heating units and analytical balances
are now available, but there is no published work
presenting an analysis of their accuracy and precision.
In the method presented by Kennedy and Phillips
(1996), drying was preceded by sample filtration and
washing. Filtration steps are time and material consuming,
and filters with pore sizes sufficiently small to retain
micro-organisms would suffer from rapid filter fouling if
used with pure fermentation samples. In this work,
microbial biomass was determined by direct application
of culture samples to a heat-resistant glass fibre pad
placed on the weighing pan and did not require filtration
and washing steps.