Sequential maltogenic α-amylase and branching enzyme treatment to modify granular corn starch

Due to the semi-crystalline structure of native starch granules, enzymatic modification of these solid, raw, entities by branching enzyme (BE) is limited. Here, we describe a method to efficiently modify starch by BE after maltogenic alpha-amylases pre-treatment. This pre-treatment produced pores at the starch granule surface, which decreased the granular yield, but increased the branching degree in starch molecules. BE post-treatments recovered the yield, increased the content of long amylose chains, and the starch crystallinity. WAXS analysis showed that BE transformed the unresolved doublet peak at 2 theta 17 degrees and 18 degrees to a strong peak at 2 theta 17 degrees, i.e. transformed the granules from the A-type to a mixed A-, B-type allomorph. Syneresis of starch gels increased with increasing BE concentrations and increased the content of slowly digested starch in retrograded starch preparations. Rheology data demonstrated that low and medium BE concentrations produced starch gels with higher G' and G'' after storage for 1day, whereas high BE concentrations reduced both G' and G''. Our data demonstrate the potential of clean, enzyme-based protocols using sequential addition of starch active enzymes for post-harvest modification of raw starch granules to obtain clean and functional starch.

Automated summary

This study describes a method to efficiently modify starch using branching enzyme (BE) after maltogenic alpha-amylases pre-treatment. The pre-treatment produced pores on the starch granule surface, decreasing granule yield but increasing branching degree. BE post-treatments recovered yield, increased long amylose chains content, and starch crystallinity.