Enzymatic modification of wheat starch by a novel maltotetraose-forming amylase from Atopomonas hussainii to retard retrogradation and improve bread quality

Abstract

To retard starch retrogradation and improve bread quality, a novel maltotetraose-forming amylase (AhMFA) from Atopomonas hussainii was expressed in Komagataella phaffii. After high cell density fermentation, the enzyme activity reached a maximum level of 3032 U mL^-1. AhMFA showed optimal activity at pH 6.0 and 55 °C, respectively. After raw wheat starch was treated with AhMFA at 55 °C for 1 h, the relative crystallinity decreased from 24.5 % to 20.8 % without changing the A-type crystalline pattern. The side chain components with A, B1 and B2 chains were reduced to 27.5 %, 44.9 %, and 13.8 %, respectively. The retrogradation enthalpy of wheat starch decreased significantly by 67.8 %. Moreover, the decreased Mixolab parameters (C5 and C5 - C4) indicated that AhMFA reduced starch retrogradation of wheat dough. After addition of AhMFA (3 ppm), the specific volume of bread increased by 29.5 % and its hardness decreased by 46.1 % compared to the control. The AhMFA-added bread exhibited good anti-staling properties with 43.7 % less hardness than the control after storage at 4 °C for 4 days. This study provided a novel maltotetraose-forming amylase for starch modification to retard retrogradation and improve bread quality.

Keywords: Anti-staling; Bread; Enzymatic modification; Maltotetraose-forming amylase; Wheat starch.