Brookfield LFRA Texture Analyzer - Manual (Page 17)

Brookfield Engineering Labs., Inc. Page 17 Manual No. M/05-370-A1205
IV. TEST METHOD DEVELOPMENT
The measurement results provided by the LFRA Texture Analyzer will be dependent on several
factors relating to the sample, the test probe, and the test parameters. A variation on any of these
elements may result in a change in measurement results. For good test repeatability it is sug-
gested that a clear and complete test method be developed. The following sections describe
these elements. It is not possible for all possibilities to be covered in this document; Brookfield
suggests that your method development include some trial and error testing to determine the best
test method for your sample material.
IV.1 Sample Preparation
The measurement of texture using the LFRA Texture Analyzer requires contact between the test
probe and the sample. The shape and surface of the sample may affect the measurement results.
Consider for example an orange: the test of a peeled orange will likely give a different result
from the test of a single wedge from the same fruit. This is likely the same for any bulk material
when compared to a neatly prepared cube of material. Consideration should be given to the
preparation of the sample to facilitate repeatability of the test. For example a material that has a
flat surface offers a consistent interface with the probe even if the material is not centered in the
test fixture. If your test sample is uneven, part of the test method could be to cut / shape / modify
the sample such that the sample is flat; consider the difference between a loaf of bread versus a
slice of bread.
IV.2 Test Probe / Fixture
The LFRA Texture Analyzer may be used with a wide variety of probes and fixtures. Brookfield
offers a set of standard items while also providing special design services. Each type of probe
offers benefits for certain sample types. The following table provides some basic guidelines.
Although this table represents our general experience, it is important to note that there are no
fixed rules for texture measurement. The main objective is to quantify your material in the best
way. This table only represents suggestions.
Probe Type Typical Application
Cylinder well defined samples with uniform surfaces,
general purpose, TPA (texture profile analysis)
Sphere samples with small scale variations on surface,
general purpose
Cone samples with rigid outer layer, often used for
penetrometry
Wire required for cutting samples
Magness Taylor required for puncturing, often used for determining
ripeness of fruit/vegetables
Extrusion Cell samples that can be made to flow, general purpose
Table V.1