Addition of 1, 4-α-glucan branching enzyme during the preparation of raw dough reduces the retrogradation and increases the slowly digestible fraction of starch in cooked noodles

Abstract

Consumers significantly prefer wheat noodles that offer both an acceptable texture and health benefits. To this end, a cold-active 1,4-α-glucan branching enzyme from Bifidobacterium longum (BlBE) was expressed in the generally recognized as safe (GRAS) host cell Bacillus subtilis and then used at 120, 240 or 480 U/g flour in the preparation of raw dough. The storage modulus and loss modulus of the BlBE-modified dough decreased, but the pseudo-plasticity increased. The cooked noodles' hardness, gumminess and chewiness decreased by 12.1%–45.8%, 9.7%–40.4% and 16.0%–42.4%, respectively, but both resilience and cohesiveness increased by 4.0%–14.8% and 1.8%–9.0%, respectively. Pearson analysis revealed a correlation between the noodles' textural parameters and the doughs' power law equation parameters. BlBE-modified noodles exhibited significantly (P < 0.05) lower differential scanning calorimetry retrogradation enthalpies during storage at 4 °C for 7 days and released significantly lower levels of glucose during incubation with mammalian α-glucosidase at 37 °C for 10 min–360 min. BlBE at 480 U/g flour increased the slowly digestible portion by 12.6%. BlBE decreased the molecular weight, x-ray diffraction crystallinity, and fourier transform infrared spectroscopy ratio of band's heights at 1045 cm−1 and 1022 cm−1 of starch but increased the amylopectin content and ratio of short- to long-branch chains. These structural changes in starch partially explained the reduced retrogradation and enhanced slowly digestible starch fraction in the noodles. © 2022 Elsevier Ltd