Heat and the Destruction of Gluten

firebrats
"What temperature is required to destroy gluten?"

This question has been asked countless times over the years. Until now, we have not had any concrete answers.

All too often the gluten-free community runs into restaurants using the same deep frier for gluten items and their gluten-free items. Of course, we know this practice is not acceptable for those requiring truly gluten-free foods, but the uneducated think otherwise.

This study appearing at the International Celiac Symposium 2017 India, shows it's quite difficult to destroy gluten with temperatures used in customary cooking methods. And when it is destroyed, it's not safe to eat [not that gluten is safe to eat in its uncarbonized state...]

Resistance of gluten immunogenic peptides (GIP) to heat elimination in a homelike environment. Lessons for cross contamination prevention.

Rodriguez Herrera A2, Garcia Sanchez M2, Lamprea Moruno M2, Monje J3, Comino I1
1 Facultad de Farmacia, Spain, 2 IHP Group, Spain, 3 Universidad Pablo de Olavide, Spain

Background
Verify effective elimination of Gluten Immunogenic Peptides (GIP) by home cooking techniques.

Methods
Batches of samples of gluten containing flour, potatoes, and potatoes plus flour matched to controls were tested. Each batch was cooked in laboratory by use of electric stove, gas stove, oil deep fryer, induction stove and water bath and was cooked at temperature range from 91-233°C (196-452 F) for 5 up to 30 minutes. GIP content was tested by GlutenTox® Sticks (KT- 5340 Biomedal Diagnostics) based on antibody G12.

Results
On gas stove was necessary to keep 233 °C (451 °F) for 10 minutes to have absence of GIP detection. In range 190-200°C (374-392°F) incubation for 30 minutes was needed to have absence of GIP detection. Tests in temperatures below 190°C (374°F) showed presence of GIP at 10 and 20 minutes.

On induction stove temperature up to 246°C (475°F) for 6 minutes was needed to have negativity to GIP. Lower temperature ranges in spite of extended time up to 30 minutes were unable to get negative GIP. In oven processing never was got negative GIP signal, in spite of processing up to 210°C (410°F) and extended incubation time up to 45 minutes.

Samples processed on electric stove, water bath and deep frying showed presence of GIP in all ranges of time and temperature.

Conclusion
It is not realistic the elimination of gluten (GIP) at home kitchen by heat as temperatures higher that 200°C (392°F) are needed. Extended processing time is no compatible with conventional recipes. Fat processing over 200 is link with toxic metabolites generation which may be harmful. Use of oven or deep frying without proper cleaning may transfer GIP to meals when previously gluten containing meals were processed in these appliances.


Source: ICDS 2017 India Abstract Book PDF



GFWDLogo

On September 14th, 2020, Gluten-Free Watchdog presented their first-of-its-kind study to the Association of Official Analytical Collaboration (AOAC) International. This study measured the amounts of gluten found in gluten-free foods when cooked in fryers that previously fried gluten-containing foods.

Like the study above, Gluten-Free Watchdog shows that gluten cross contact in shared fryers is problematic for individuals with gluten-related disorders.

“Gluten-free foods cooked in shared fryers with wheat: A pilot study assessing gluten cross contact.”

Introduction

Dietitians have long been discouraging consumers with celiac disease (CD) from ordering gluten-free foods cooked in shared fryers at restaurants.

This recommendation is based on presumed gluten exposure versus evidence-based research that gluten cross contact occurs. To the best of the authors’ knowledge there is no published data on gluten levels of gluten-free foods after cooking in shared fryers.

The lack of evidence of cross contact contributes to confusion among consumers, especially when gluten-free foods cooked in shared fryers (e.g., fries) are marked as gluten-free on some restaurant menus.

The purpose of the present study is to help inform consumer recommendations by assessing gluten levels of fries free of gluten-containing ingredients cooked in shared fryers with wheat.

Results

The sandwich R5 ELISA found quantifiable levels of gluten in 9 of 20 (45%) orders of fries ranging from 7 to > 84 parts per million (ppm)(above the highest standard) (Table 1).

Five orders (25%) of fries tested above 20 ppm of gluten.

Fries from 6 of the 10 (60%) restaurants were found to contain quantifiable levels of gluten in at least 1 of the 2 orders, with fries from 4 of these 6 restaurants found to contain levels above 20 ppm of gluten in at least 1 of the 2 orders.

The competitive R5 ELISA found gluten in 3 of the 20 (15%) orders of fries ranging from 14 to > 283 ppm gluten (above the highest standard).

Summary

Results of this assessment suggest that gluten cross contact may occur when gluten free foods are cooked in shared fryers with wheat. While a much larger study may be warranted, it remains prudent to advise consumers with CD to avoid foods cooked in shared fryers.

It is impossible for a consumer to know how much gluten is in fryer oil and how much gluten may end up in an order of fries. Shared holding trays, scoops, and fryer baskets also are sources of potential cross contact.

The gluten levels reported in this investigation are likely underestimates due to the limitations of the analytical methods available for gluten analysis of foods heated to high temperatures


For more information (including PowerPoint presentation, video, and white paper):
http://bit.ly/GFWD-French-Fry-Study


Updates:
9/27/20 - Added Gluten-Free Watchdog’s study.