Abstract:Tapioca starch is widely applied in the food industry. However, it usually requires modification before it can be used in food. Compared to traditional modification techniques, enzymatic modification has become a research hotspot in the field of starch due to its environmental friendliness, minimal by-product generation, and high yield. In this study, a starch branching enzyme(GBE) derived from the extreme thermophilic bacterium Rho-dothermus obamensis STB05 (Ro-GBE) was used for the purpose of catalyzing the highly branching modification of tapioca starch. The effects of this modification on the molecular structure, stability, and in vitro digestibility of cassava starch were systematically investigated. The results showed that after modification with an enzyme dosage of 100 U/g and a reaction time of 12 h, the resulting product exhibited an α-1,6 glycosidic bond ratio of 7.85%, which represents an increase of 152.41% over that of native tapioca starch. Additionally, the ratio of long-chain molecules in the modified starch decreased, while the short-chain proportion increased, and the average chain length was reduced. Furthermore, stability tests on tapioca starch paste indicated that the highly branched modification improved properties such as solubility, precipitation stability, transparency stability, and freeze-thaw stability. The results from the in vitro digestion experiments revealed a reduction in the digestibility of the modified starch. These findings provide a preliminary theoretical basis for biological modification of tapioca starch and its industrial application.
