Degradation of Gluten in Wheat Bran and Bread Drink by Means of a Proline-Specific Peptidase

Theresa Walter

doi:10.4172/2155-9600.1000293

Abstract

Gluten-free wheat bran and bread drink were produced by degrading gluten with Aspergillus niger prolyl endopeptidase (AN-PEP). For this purpose, bran from native and germinated wheat grains as well as bread drink were mixed with AN-PEP and incubated at 50°C under different conditions. The amount of enzyme activity (1.2 • 10-4 - 8.7 • 10-1 U), the incubation time (0-72 h), and the pH value (1.0-9.0) were systematically altered. The gluten content was monitored by a competitive ELISA using the R5 antibody. Gluten in two wheat bran samples produced in the laboratory was degraded below the threshold for gluten-free foods of 20 mg/kg. This was not possible in a commercial wheat bran sample that had potentially been heat-treated leading to strong crosslinking of gluten by incorporation of gliadins into the glutenin fraction, possible formation of isopeptide crosslinks and, thus, poor digestibility. In contrast, gluten in bread drink was easily degraded after a short incubation time of 30 min and low AN-PEP activity. No significant differences of the quality parameters between treated and untreated products were found. Remarkably, bran from germinated grains was strongly enriched in nutritionally positive compounds such as dietary fiber and folates compared to native grains. Thus, wheat bran from germinated grains rendered gluten-free by treatment with AN-PEP can contribute to increasing the nutritional value of the gluten-free diet.

Highlights

Celiac disease (CD), called gluten-sensitive enteropathy, is an inflammatory disorder of the upper small intestine, affecting about 1% genetically predisposed individuals of the Western population
The gluten content of bran 2 was even reduced below the limit of quantitation (LOQ; 10 mg gluten/kg) of the ELISA method after a longer incubation time (48 h) with a lower enzyme concentration (0.12 U)
Aspergillus niger prolyl endopeptidase (AN-PEP) appears to be the enzyme of choice because it manages to degrade even very high gluten concentrations (≈100,000 mg/kg) in different matrices at pH values between 1.0 and 4.0 and temperatures between 40 and 50°C without any adverse effects

Summary

Introduction

Celiac disease (CD), called gluten-sensitive enteropathy, is an inflammatory disorder of the upper small intestine, affecting about 1% genetically predisposed individuals of the Western population. It is one of the most frequent food intolerances worldwide. Storage proteins from wheat, rye, barley, and possibly oats, which are called gluten in the field of CD, trigger an immune response in the small intestine leading to an inflammation and to the destruction of the microvilli necessary for the absorption of nutrients. Dietetic gluten-free products are regulated by the Codex Alimentarius Standard as well as the Commission Regulation (EC) No 41/2009. Products with gluten contents between 20 and 100 mg/kg can be declared as “low in gluten”

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