Thermo-reversible inhibition makes aqualysin 1 from Thermus aquaticus a potent tool for studying the contribution of the wheat gluten network to the crumb texture of fresh bread

Abstract

The thermo-active serine peptidase aqualysin 1 (Aq1) of Thermus aquaticus was applied in bread making to study the relative contribution of thermoset gluten to bread crumb texture. Aq1 is active between 30 °C and 90 °C with an optimum activity temperature of around 65 °C. It is inhibited by wheat endogenous serine peptidase inhibitors during dough mixing and fermentation and starts hydrolyzing gluten proteins during baking above 80 °C when the enzyme is no longer inhibited and most of the starch is gelatinized and contributes to structure formation. Aq1 activity reduced the molecular weight of gluten proteins and significantly increased their extractability in sodium dodecyl sulfate containing medium. While it had no impact on the specific bread volume and only limited impact on hardness, cohesiveness, springiness, resilience and chewiness, it impacted bread crumb coherence. We conclude that starch has a greater impact on crumb texture than thermoset gluten.

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

“…The MW distributions of proteins extracted from the heated GSB doughs under reducing conditions with SDS containing medium (SDS‐EP‐R) were evaluated with SE‐HPLC as in Verbauwhede et al. (2018). The profiles were divided into HMW (MW exceeding 18.4 k) and LMW (MW lower than 18.4 k) protein, and the levels of SDS‐EP‐R were calculated as in Verbauwhede et al.…”

“…It is hence of interest to impact on gluten during different stages of bread baking. That aqualysin 1 (Aq1) is subject to heat‐sensitive inhibition makes it a potent tool for studying the contribution of gluten to bread loaf volume, crumb structure, and texture (Verbauwhede et al., 2018; Verbauwhede, Lambrecht, Fierens, et al, 2019; Verbauwhede, Lambrecht, Jekle, et al, 2019). In addition, appropriate peptidase use results in soft fresh bread crumb and delays crumb firming and the subsequent increase of its chewiness during storage (Caballero, Gomez, & Rosell, 2007; Indrani, Prabhasankar, & Venkateswara Rao, 2003; Mathewson, 2000).…”

“…Its four cysteine residues form two disulfide bonds (Kwon et al., 1988) which contribute to its thermostability by stabilizing the conformation of the catalytic site (Sakaguchi et al., 2008). Aq1 is active in a 30°C to 90°C temperature interval with optimal activity at about 65°C and pH 10 (Verbauwhede et al., 2018). Verbauwhede et al.…”

“…Verbauwhede et al. (2018) reported for the first time that in bread making Aq1 only starts hydrolyzing wheat proteins at about 80°C and that this is because wheat endogenous serine peptidase inhibitors block its activity in the earlier stages of the process. Also, in vitro inhibition of Aq1 by extracts of wheat flour is concentration and temperature dependent (Verbauwhede et al., 2018).…”

Wheat Seed Proteins: Factors Influencing Their Content, Composition, and Technological Properties, and Strategies to Reduce Adverse Reactions

“…This network is important for bread quality, affecting loaf volume, crumb structure, and initial texture (Delcour et al., ). A recent study used a thermoactive peptidase to show that the gluten network contributes mainly to the coherence of the crumb and less to the texture and the final bread volume (Verbauwhede et al., ).…”