The Effect of α-, β- and γ-Cyclodextrin on Wheat Dough and Bread Properties

Effect of cyclodextrin glucosyltransferase extracted from Bacillus xiaoxiensis on wheat dough and bread properties

In this study, the cyclodextrin glucosyltransferase (CGTase) was extracted from Bacillus xiaoxiensis. CGTase had negative effects on dough viscoelastic properties and gluten strength but had positive effects on bread baking qualities and anti-staling properties. Adding an appropriate amount of CGTase (less than 0.3 U/g) could improve the specific volume, crumb texture, crust color, moisture content, and crumb hardness of bread. The bread crumb with 0.4 U/g CGTase (based on flour weight) had the lowest retrogradation enthalpy of 0.53 ± 0.10 J/g and the lowest relative crystallinity of 16.1%, which indicated the alleviating effect of amylopectin crystallization. Moreover, CGTase reduced the moisture from forming crystal lattices and limited starch molecule migration. The T₂ transverse relaxation results showed that the increase of immobilized water content in the bread with CGTase was lower than the control after 5 days of storage, which implied the water-holding capacity of the bread was enhanced and provided information on the inhibition of water migration. Hence, the CGTase could be a potential bread improver.

Highlight on mutations affecting the US132 cyclodextrin glucanotransferase binding specificity, thermal stability, and anti-staling activity

We have already reported that the triple mutant (K47E-S382P-N655S of Paenibacillus pabuli US132 cyclodextrin glucanotransferase US132 (CGTase)) altered the CGTase specificity. In the current study, the single (K47E, S382P and N655S) and double (K47E+S382P, K47E+N655S, and S382P+N655S) mutants were constructed to elucidate the synergic or antagonist substitutions effect on the enzyme behavior. For the six generated mutants, an improvement of the dextrinization/cyclization ratio from 4.4 to 6-fold was observed when compared to the wild-type enzyme. The mutations effect on enzyme specificity was not attributed to synergy modulation since the single mutant N655S had the highest ratio enhancement. Moreover, the mutant N655S revealed the highest β-cyclodextrin binding affinity with a high amount of hydrophobic bonds which might be contributed to the apparent decrease in the cyclization activity. On the other hand, mutations N655S, K47E, and (K47E-N655S) showed the same positive effect on thermal activity. The highest stability was attained at 70 °C by N655S to be 3.6-fold higher than the wild-type. The addition of N655S to wheat flour induced a decrease of dough and bread hardness and led to an increase in dough and bread cohesiveness and a rise in bread masticability values compared to the control. This mutant addition also corrected the dough elasticity decrease engendered by the wild-type CGTase indicating that N655S-CGTase could be an alternative anti-staling agent.