Table 1.

Effects of extrusion on starch molecular structure.

Starch Type	Changes in Starch Molecular Structure	Mechanism	Reference
Genetically modified corn starches	(1) Amylopectin undergoes significant degradation during extrusion, while the size distribution of amylose does not seem to vary notably; (2) No qualitative differences in SEC weight distributions of debranched starch between native and extruded starches.	(1) The susceptibility of starch to shear degradation depends on molecular size and branching structure; (2) The shear degradation of starch during extrusion preferentially cleaves off branch points (α-1,6-linkages).	[35,44]
Rice starch	(1) Most degradation by extrusion occurs on amylopectin molecules; (2) Chain-length distribution of debranched rice starch and extruded samples reveals no significant differences.	(1) Amylopectin is more sensitive to degradation than amylose by extrusion because of its higher branching degree and larger molecular size; (2) Glycosidic bonds near amylopectin branching points are susceptible to shear degradation during extrusion.	[19,39]
Wheat starch	Amylopectin fraction with high molecular size decreases while the fraction in the molecular size range of amylose increases.	Preferential degradation on amylopectin.	[36]
Green banana flour	Amylose content increases in green banana starch after extrusion (from 16.2% to 17.3–33.5%).	Preferential cleavage of amylopectin α-1,6-glycosidic bonds under shearing force in the extruder.	[40]
Jackfruit seed starch (JFSS)	(1) Molecular weight, radius of gyration, relative crystallinity of starch are notably decreased while amylose content is not changed by improved extrusion cooking technology (IECT); (2) B2 and B3+ chains of JFSS are converted to A and B1 chains after IECT treatment.	IECT breaks α-1,4-glycosidic bonds in amylopectin backbone.	[38]
High-amylose maize flour (HAMF), normal maize flour (NMF)	Amylose content of HAMF considerably decreased, while that of NMF increased after extrusion.	The decrease in amylose content in HAMF may be induced by its high amylose and lipid content, where excessive leaching of amylose is bound with free lipids to form amylose–lipid complex during extrusion.	[41]