Effects of Streptococcus thermophilus GtfB enzyme on dough rheology, bread quality and starch digestibility

Abstract

It is highly desirable to produce bread with both acceptable texture and health benefits. Glucosyltransferase B (GtfB), an enzyme with activities of 4,6-alpha-glucanotransferase, could increase the number of short branches and percentage of (alpha 1 -> 6.) linkages in starch, resulting in slow digestibility and low retrogradation properties of starch. In this study, Streptococcus thermophilus GtfB enzymes were applied in the preparation of wheat flour dough and bread. With the addition of GtfB at 0.04-0.16 U/g flour, the smaller storage modulus (G') and loss modulus (G '') of doughs over a frequency sweep range of 0.01-20 Hz were observed, and the specific volumes and the slowly digestible starch (SDS) contents of breads were increased by 2.3-11.4% and 19.7-35.0% (P < 0.05), respectively. GtfB-modified breads were softer and less gummy and chewy (P < 0.05) after storage at 4 degrees C for 7 days. Thus, these results suggest that S. thermophilus GtfB could be applied to improve the textural and digestive properties of bread.