Transia Plate Gluten - IUL Instruments GmbH

Transia Plate
Gluten
Result interpretation -
semi-quantitative assay
Validation of the test
The mean optical density (OD) of the negative controls
must be lower than 0.15. If not, the results are
not valid. Repeat the ELISA, taking extra care that all
the reagents are at room temperature and that the
washing step is performed correctly.
Gluten content
As defined by the Codex Alimentarius Commission in
1981 (Codex Standard for “Gluten-free” Foods, STAN
118-198, Food Agriculture Organisation/World Health
Organisation, Rome, Italy), products labelled glutenfree
may not contain more than 200 ppm (0.02%)
gluten.
Compare the mean OD of the sample with the mean
OD of the reference starches.
If the OD of the sample diluted 1/50 is lower than the
OD of starch A then the product may be labelled
“gluten-free”.
If the OD of the sample diluted 1/50 is higher than
the OD of starch A, but the OD of the sample diluted
1/250 is lower than the OD of starch B, then the
gluten level should be measured quantitatively to
determine if the product could be labelled “glutenfree”
or not.
If the OD of the sample diluted 1/250 is higher than
the OD of starch B, but the OD of the sample diluted
1/1,000 is lower than the OD of starch C, then the
label “gluten-free” is not acceptable.
If the OD of the sample diluted 1/1,000 is higher than
the OD of starch C then the label “gluten-free” is not
acceptable.
Result interpretation -
quantitative assay
Validation of the test
The mean OD of the negative controls must be lower
than 0.15.
The standards must meet the following requirements:
Dilution Standard OD
3 0.20 µg/mL ≥ 0.800
4 0.16 µg/mL ≥ 0.650
5 0.08 µg/mL ≥ 0.350
6 0.04 µg/mL ≥ 0.200
7 0.02 µg/mL ≥ 0.100
8 0.01 µg/mL ≥ 0.070
If the standards do not meet the requirements, repeat
the ELISA, taking extra care that all reagents are at
room temperature and that the washing step is performed
correctly.
Gluten content
Using a lin-lin graph paper, draw a standard curve
with the OD of the standards on the y-axis and the
concentration [µg/mL] on the x-axis. An example of a
standard curve is given in Appendix B.
Plot the mean OD of the chosen sample dilution on
the standard curve. Read the gliadin concentration
(G) of the sample dilution.
Note the gliadin concentration on the work sheet
(ENR COM 113) and calculate the gluten content by
using the following equation.
% gluten = G x D x 2 x 10 /10,000
G = gliadin concentration read from the standard
curve
D = dilution factor of the extract (e.g. 50, 250…)
Factor 2 ⇒ it is estimated that 50% of the protein in
gluten is in the form of gliadin.
Factor 10 ⇒ 10 mL of extraction solution is used for
1g of sample
Factor 10,000 ⇒ converts the concentration from
µg/g into %
See Appendix A for conversion from % to ppm.
NOT COM 111E 11/00
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