Chemistry Reference
In-Depth Information
influence is exerted on the results. This can be thought of as an
extra lens available to the magnifying glass analogy to sharpen the
image.
(iii)
How will the results be used?
Here, one considers the final audience
who will receive the results, should they be journal article readers,
conference delegates/fellow rheologists, colleagues, customers or
the layman. Whichever group, the intended audience alters the
manner in which the data are presented, to what level it is discussed
and which form the interpretive style will take. This requires the
rheologist to possess sound and robust communication skills to be
adept at presenting material in the different styles needed.
Assimilating all the information from the questions asked earlier, the
rheologist should now be able predict what the outcome of the results
will look like. This can be sketched out as a guide, and if the measured
results match the predicted results, then the theory and set-up of the
rheometer were likely correct. From these basic tenets, the rheologists
are now ready to begin measuring their sample, and subsequently explore
their data to explain their findings using the interpretive method. In order
to demonstrate this approach, a worked case study is presented in the
following section.
1.1.1
Case study
Wine gums and the art of making them are governed by the setting
temperature of the system. High-ester pectin can be used to make ex-
cellent wine gums, but the setting temperature is high, typically around
70-80
◦
C. This in itself presents possible application limits on the use of
wine gum syrup, i.e. it makes filling it into chocolate cups unrealistic.
How can this problem be solved, quantified and controlled?
High-ester pectin sets in the presence of a co-solute (sugar) as a
function of temperature or pH (acidity). Cold setting of pectin is pos-
sible and has been documented, but has focused on low-ester pectin
(Gilsenan
et al
., 2000; Lootens
et al
., 2003), typically not used in wine
gums. Controlling the acidification of the wine gum mass by means of
glucono-δ-lactone (GDL) allows gelation of high-ester pectin to occur
over ambient temperatures (Madsen and Thulin, 2002; Young, 2007).
Discussion now, as regards the rheology, centred on how to measure
this gelation profile. Small deformation oscillation is performed with
constant small strain; within the linear viscoelastic region, temperature
is kept constant - room temperature (23
◦
C) - and the frequency of
oscillation is kept constant, 0.5 Hz.
Predictions were made of the type of curve to be seen. Focusing on
the phase angle curve against time, we expect to see a high phase angle
