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Helipath measurement

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by

Lydia Asri

on 29 August 2013

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Transcript of Helipath measurement

The Helipath Mistery
A preliminary study has been done to develop a method for measurement using Helipath. Nevertheless due to time and resource constrains this study has left some points to be improved that were taken into account in this study:

- Fixed travel height of the spindle
- Fixed lead time from pouring water until the start of measurement: 1 min
- Tall beaker with diameter 61,5mm as a sample cup to enable the forming of a higher foam layer and to have better solubilisation
- Spindle TB were chosen based on of several factor.
The larger the spindle, the lower the viscosity range it can measure. TA is the larger spindle, but TA is not an option to be combined with the tall beaker (separate study on wall effect is done and available)
- The amount of foamer used in the recipe is decrease to 8 gr for better solubilisation.
Experimental set up

Method:
- Travel height: 25mm
- Tall beaker as sample cup
- Spindle type: TB
- Recipe: 8 gr foamer+2 gr coffee in 150 ml hot water
- Rotation speed: 1 rpm, 2 rpm, 3 rpm


Discussion
Helipath is a very sensitive tool, any small difference in a sample will be reflected in the result.
Objective of experiments
Evaluate and approach the possibility to measure foam texture using Brookfield Viscosimeter with Helipath stand.

Background
Instrument: Brookfield Viscometer with helipath T-bar spindle
Materials:
Samples 22M, 30G, 26K, 25H, 23H, 21A, 25C
Kraft reference coffee
Correlation of Spindle type, Rotational speed and Torque Value
Spindle and speed combination is chosen based on several factor.

1. Torque
One of the goal is to obtain a %torque reading between 10 and 100 as the relative error of measurement improves as the reading reach 100.

2. Spindle factor
The goal is to select combination of speed/spindle whose range brackets the estimated sample viscosity.

3. Rotational speed
The use of higher rotational speed would result in higher torque reading and lower viscosity reading.


TB 1 rpm
TB 2 rpm
TB 3 rpm
Overview of measurement using different rotation speed
Parameter
Fixed parameter:
-
Tall beaker (61.5 mm)
- Spindle TB
- Travel height

Variable parameter:
Rotation speed: 1 rpm, 2 rpm and 3 rpm
Which speed is most suitable ?
Well, Let's look through statistical glass
TB 1 rpm
want some details?
want some details?
TB 2 rpm
TB 3 rpm
want some detail?
How is the reliability?
reproducibility?
TB 3 rpm
TB 2 rpm
TB 1 rpm
As a consequences, small differences in sample weight, stirring time/style can differ the result which result in not so good repeatability, specially in bad soluble sample such as 26K
With all the limitations that we have, the question is:
How good is good enough?
Helipath can be useful to group foamers in a different level of firmness and stability to create a foam texture map for the portfolio
And how can we make use of this instrument properly?
As long as sample preparation is still done manually, there will always be variation. Maybe we can think of a way to automate the sample preparation...
But one has to keep in mind that this instrument and the method has limitations and therefore is not recommended to zoom in the precise value for comparing samples which are closely alike
Plotting the measurement to "a value"
Another approach is to generate trendline based on the peak values. Two trendlines can be generated, the odds peaks trendlines and the even peaks trendlines. The odds peaks represent the measurement when the spindle goes inside the foam and the even represent the value when the spindle goes out of the foam.

Plotting maximum viscosity as y axis and foam firmness stability (lowest peak viscosity/maximum viscosity x 100) as x axis.
The disadvantages is that in some foamer the lowest peak is not always the last peak and the highest peak is not always the first peak so we can not always compare using the same time interval. Other disadvantages is that the foam firmness stability rely only on two peak points.

1. Former study of Rineke
2. Trendlines
Trendline
Rineke's approach
Application test
In summary..
Brookfield Viscometer with Helipath T-Bar spindle
lower limit
lower limit
lower limit
This instrument are not designed to measure viscosity below the lower limit and samples with torque less than 10%
This instrument are not designed to measure viscosity below the lower limit and samples with torque less than 10%
This instrument are not designed to measure viscosity below the lower limit and samples with torque less than 10%
For zooming in the difference between samples, it is recommended to also compare the graphs generated from the measurement itself.
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