Resistant structure of extruded starch: Effects of fatty acids with different chain lengths and degree of unsaturation

This study investigated the formation mechanism of enzyme-resistant structures in extruded starch, specifically, fatty acid-starch complexes (FASCs). The effects of fatty acids (FAs) with different carbon-chain lengths (C12-C18) and degrees of unsaturation (C18:0-C18:2) on complex formation were evaluated, with fluorescence microscopy verifying complex formation. The complexed-lipid content and degree of relative crystallinity increased with the carbon-chain length and degree of FA unsaturation. FAs with fewer carbons were more likely to generate stable complexes (e.g., form II, melted at 100-120 degrees C), while FAs with more carbons tended to produce relatively unstable complexes (e.g., form I, melted at 80-100 degrees C). After reheating and cooling, a new amylose-lipid complex and an amylose-amylopectin network was formed in the unsaturated FASC samples, which restricted the penetration of enzymes into starch granules. A starch-linoleic acid complex exhibited the highest resistant starch content (15.7%) and lowest predicted glycaemic index (88.4).

Automated summary

This study investigated the formation mechanism of enzyme-resistant structures in extruded starch, specifically, fatty acid-starch complexes (FASCs). The effects of fatty acids with different carbon-chain lengths and degrees of unsaturation on complex formation were evaluated. The results showed that fatty acids with shorter carbon chains and higher unsaturation tended to form more stable complexes. Reheating and cooling led to the formation of new complexes and starch networks, limiting enzyme penetration into starch granules.