Characterization of enzymatically modified rice and barley starches with amylosucrase at scale-up production

Physicochemical properties of Neisseria polysaccharea amylosucrase (NpAS)-treated rice and barley starches were investigated at scale-up production. Pre-gelatinized rice and barley starches were treated with significantly lower NpAS dose (0.1 U/mL) but 100 times larger reaction volume (3500 mL), compared to the analytical scale (35 mL) used in the previous study. NpAS-treated starches in this scale-up production were characterized with respect to reaction efficiency (RE), resistant starch (RS) content, amylopectin (AP) branch-chain length distribution, solubility, swelling power, pasting viscosity, and thermal transition properties. The RE enhanced up to 1.8 times by increasing the reaction volume, which improved the RS content and AP branch-chain lengths of NpAS-treated starches. Compared with the native starch, NpAS-treated starches exhibited lower solubility and swelling power, lower pasting viscosity, and a large increase in the melting peak temperature. Consequently, NpAS treatment of pre-gelatinized starches in this study would be a potential way of replacing commercial RS production.