Heat‐sensitive inhibition of aqualysin 1 by protein containing wheat, maize, and barley extracts

Background and objectives Wheat flour proteins inhibit the thermo‐active serine peptidase aqualysin 1 (Aq1) from Thermus aquaticus in a temperature‐dependent way. The impact of aqueous flour extracts (FEs) from maize, barley, or rice on Aq1 activity both in an assay and in a gluten‐starch model system (GSMS) for bread making was investigated. Findings The degree of Aq1 inhibition by maize and barley FEs decreased at temperatures exceeding 50°C. With higher levels of FEs, higher temperatures were required to undo inhibition. Rice FEs did not inhibit Aq1. Gluten hydrolysis started at lower temperatures in GSMS containing maize FE rather than wheat FE. Incubating Aq1 with maize FE prior to inclusion in GSMS containing wheat FE decreased the onset temperature of Aq1 activity. Conclusions In presence of their FEs, the onset and optimal temperatures for Aq1 activity increased in the order maize, wheat, and barley. When Aq1 was incubated with maize inhibitors prior to dough making, wheat inhibitors still impacted Aq1 activity. Significance and novelty That maize and barley contain inhibitors inactivating Aq1 in a heat‐sensitive way different from that exerted by those in wheat is novel and relevant in the context of the production of multigrain bread products.