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U.S. Department of Health and Human Services

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Gluten-Free Food Labeling - Text Version of PowerPoint Presentation by Jupiter Yeung

Slide 1 - Commercial Gluten Test Kits / Methods

Jupiter Yeung, PhD
Principal Scientist
Food Products Association

FDA Gluten Free Meeting, Aug 19, 2005

photo - FPA logo

Slide 2 - Gliadin Detection Methods

  • Immunochemical
    • ELISA
    • Lateral Flow Device
    • Immunoblotting
  • PCR
  • MS
    • MALDI-TOF
    • LC/MS/MS

photo - FPA logo

Slide 3 - Sandwhich ELISA

photo - diagram displaying how sandwich ELISA works

photo - FPA logo

Slide 4 - Gliadin Antibodies Specificity

  • Skerritt mAb
    • omega-gliadin (alpha-gliadin)
    • wheat - 100%, rye - 120%, barley - 5%
  • Mendez R5 mAb
    • QXPFP toxic epitopes of alpha, beta, gamma, omega-gliadins
    • Equally to wheat, rye and barley
  • Both Ab recognize raw and cooked prolamins

photo - FPA logo

Slide 5 - Commercial Gliadin ELISA Kits

Company
Product
LOD*
LOQ*
Range*
Replicates
Costs
Neogen
Alert (Qualitative)
10
  
1
$237/20Sampl
Veratox
 
5
5-50
1
$465/38Sampl
R-Biopharm
RidaScreen
1.5
2.5
2.5-40
2
$425/96 wells
RidaScreen Fast
5
5
5-40
1
$400/48 wells
Tepnel
Gluten Assay Kit, AOAC                          or High sensitivity
5
50
50-1000
2
$425/96 wells
0.5
5
5-100
2
Hallmark
HAVen Gluten, AOAC
or High sensitivity
5
50
50-1000
2
$425/96 wells
0.5
5
5-100
2
Diffchamb
Transia Plate Gluten
5
5
5-100
2
$500/96 wells
Transia Plate Prolamins
1.5
 0.8
0.8-12.5
2
$500/96 wells
Morinaga
Wheat Protein
0.3*
3.12
3.12-20
2
$600/96 wells

* ppm gliadin

ppm gluten = ppm gliadin x 2

blue cells = Converted to ppm from micro-g/mL

photo - FPA logo

Slide 6 - Commercial Gliadin ELISA Kits

Company
Product
Validation
Neogen
Alert
 
Veratox
 
R-Biopharm
RidaScreen
 
RidaScreen Fast
PWG ring trial
Tepnel
BioKit Gluten
(AOAC OM)
       High Sensitivity
 
Hallmark
HAVen Gluten
(AOAC OM)
       High Sensitivity
 
Diffchamb
Transia Plate Gluten
NFA, Sweden
Transia Plate Prolamins
 
Morinaga
Wheat Protein
NIHS, Japan

photo - FPA logo

Slide 7 - Gliadin ELISA

photo - ELISA test tray

photo - FPA logo

Slide 8 - Lateral Flow Device (Dipstick)

Company
Product
LOD (ppm gluten)
 
Costs
R-Biopharm
Rida Quick
10
 $200 / 20 strips
Tepnel
Gluten Rapid
100
$150 / 10 strips
Gluten Home
100
$ 75 / 5 strips

*Positive can mean less than LOD

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Slide 9 - Lateral Flow Device

photo - strip text diagram

photo - FPA logo

Slide 10 - Lateral Flow Device

photo - lateral flow diagram showing procedure and interpretation

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Slide 11 - Lateral Flow Device

photo - lateral flow device results displaying negative, positive and very high level results

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Slide 12 - Issues with Gluten Test Kits

  • Ab has different specificities to different prolamins, e.g. Skerritt Ab
  • Various results from different extraction media: 4060% EtOH, cocktails
  • Different standards used from different kits
  • False positives and negatives require a confirmatory test
  • Limited availability of confirmatory test to most food lab
  • No sampling plan

photo - FPA logo

Slide 13 - Extraction Media

  • Aq. Alcohol (4060% EtOH)
  • Cocktail (reducing agent + others)
    • interaction of Ab and Ag

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Slide 14 - Matrix Effect

  • Cocktail (reducing agent + others)
    • interference with complex food matrices, e.g. milk
    • interaction of Ab and Ag
  • Samples with high polyphenols, tannins and syrups require fish gelatin to improve recovery

photo - FPA logo

Slide 15 - Effects of Extraction Media

photo - table of effects of extraction media data

Hasselberg et al. Proceeding of the 18th Meeting, WPGAT, 2004

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Slide 16 - Effect of Partial Hydrolysis

photo - bar graph showing effect of partial hydrolysis data

Ferre et al. Proceeding of the 18th Meeting, WPGAT, 2004

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Slide 17 - Reference Materials

  • IRMM480 Wheat Gliadin
  • NIST
    • SRM 1567a Wheat Flour
    • RM 8418 Wheat Gluten
    • RM 8436, 8437, 8438, 8441a
  • Others

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Slide 18 - Confirmation Methods

  • AbWestern blot
  • PCR qualitative, quantitative
  • MS MALDITOF, LC/MS/MS

photo - FPA logo

Slide 20

photo - line graph displaying gliadin profile data

Garcia et al., Proceeding of the 18th Meeting, WPGAT, 2004

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Slide 20 - Detection & Speciation

 
Wheat
Gliadins
Rye
Scalins
Barley
Hordeins
Oat
Avenins
Ab-based
+
-
PCR
+
+
+
+
MS
+
+
+
+

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