Effects of Mutant Thermostable alpha-Amylases on Rheological Properties of Wheat Dough and Bread.

Thermostable mutant (alpha)-amylases (21B, M111, and M77) with various degrees of thermostability were purified from Bacillus amyloliquefaciens F and used as improvers for breadmaking. Test baking with the mutant enzymes was conducted using the long fermentation sponge-dough method. Addition of an appropriate amount of mutant alpha-amylases to the ingredients distinctly increased the specific volume of the bread and improved the softness of breadcrumb as compared with the addition of Novamyl (NM), an exo-type alpha-amylase. M77 was the most effective in retarding the staleness of breadcrumb. The softness of breadcrumb during storage, however, was not correlated with the thermostability. All mutant alpha-amylases weakened the mixing property of the dough, whereas they strengthened the property of fermented dough. Especially, M77 and NM had different effects on the dough properties, but their bread qualities were similar to each other. The strong tolerance of M77 dough to the long baking process might be due to the production of hydrolyzed starches, oligosaccharides in the range of maltopentaose to maltohexaose, as compared with NM. Therefore, in the light of present findings, these mutant alphaamylases are possible substitutes for NM as bread improvers.