AOAC ERP Gluten Assays - Dec 2018

Annex B

Figure 4. Reactivity of the HMW-GS antibody system against different fractions from wheat or rye; all fractions were tested at concentrations between 5 ng/mL and 80 ng/mL; the HMW-GS antibody was coated to microtiter plates and used in the conjugate.

OD 450 nm

3.5

3.0

Wheat prolamins

2.5

Wheat HMW-GS

Rye prolamins

2.0

Rye glutelins

1.5

1.0

0.5

0.0

0

20

40

60

80

100

Concentration (ng/ml)

The barley glutelins (D-hordeins) are quite different to all other gluten proteins (Data base: UniProt). It is therefore not surprising that none of the antibodies raised against rye secalins (R5), LMW-GS or a HMW-GS peptide reacts noticeably with this fraction. However, D-hordeins represent only about 5% of gluten proteins in barley (13).

4.1.3 Selectivity Study: Cross reactivities The cross reactivity panel (table 1 and 2) is slightly modified but still according to Koerner et al. (14) and represents the opinion of the AOAC Allergen community. Some commodities were added to the list due to long lasting experiences of the manufacturer. In total, 83 commodities were tested. The commodities were extracted once like a sample with Cocktail/80% ethanol (3.8) and were tested in the RIDASCREEN ® Total Gluten. Some commodities were tested by adding skim milk powder to mask the interference by polyphenols (3.8). Tables 1 and 2 clearly show that no cross-reactivity (OD of sample > OD of standard 2) exists against the 83 tested commodities. A lot of these commodities are used to compose alternative food for CD patients.

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RIDASCREEN ® Total Gluten In-house validation report 2018-10-21