Journal of Nutrition & Food Sciences
Open Access

Abstract

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

Theresa Walter, Herbert Wieser and Peter Koehler

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.