Improved production of gamma-cyclodextrin from high-concentrated starch using enzyme pretreatment under swelling condition

High substrate viscosity during the production process suppressed the formation of gamma-cyclodextrin (γ-CD) from starch. Although liquefaction can be carried out by enzymes with high temperature optimum, some CGTases of interest are not suitable due to loss of activity at the gelatinization temperature. In order to apply a gamma-cyclodextrin glucosyltransferase (γ-CGTase) with an optimum temperature of 50 °C to the liquefaction of 10% w/v cassava starch, an improved process combining moderate heat treatment (30 °C increased to 70 °C) with enzymatic treatment was established. The substrate viscosity dropped from 2456 to 23 cP after the pretreatment, and the rate of γ-CD production increased from 10.43 to 26.34%. This process was further applied to the liquefaction of 30% w/v cassava starch, and the pretreated substrate was finally converted into 21.81% γ-CD. In general, evaluation indicators and basic principles of starch pretreatment were established, providing a reference for the production of γ-CD.