Structural modification of starch by pullulanase improves the quality of sweet potato starch noodles

Pullulanase (PUL) is a starch-debranching enzyme that specifically hydrolyzes the α-1,6-glycosidic bonds at the branch points of amylopectin, yielding amylose and oligosaccharide chains. These products are widely utilized to modify starch properties. However, the effects of PUL on the characteristics of sweet potato starch (SPS)-based noodles remain unclear and warrant further investigation. Herein, the impact of PUL on the physicochemical properties of SPS and SPS-derived starch noodles is systematically examined.

With the addition of PUL, surface cracking of starch granules increased, indicating its hydrolytic effect on SPS. Improvements were observed in light transmittance, viscosity, retrogradation value, thermal stability, and gel strength, while solubility demonstrated noticeable changes. Notably, the texture and cooking quality of SPS-based noodles were remarkably enhanced. Correlation analysis revealed that the cooking quality of noodles was closely associated with the structural changes in starch. PUL reduced long- and short-range molecular orders, loosening the double-helix structure and thereby enhancing the gelling property of SPS. However, excessive PUL dosage led to starch chain rearrangement, reinforcing the double-helix structure and strengthening the crystalline order, which in turn diminished gelatinization and gel strength.

An appropriate amount of PUL addition could enhance the quality of SPS-based noodles, and the dosage is approximately 50 U g^-1 starch. The findings could expand the application scope of PUL and provide a theoretical basis for the green preparation of SPS noodles in practical production. © 2025 Society of Chemical Industry.