Structural characteristics of linear dextrin and in vitro digestion of lauric acid complexes generated via gradient alcohol precipitation

Linear dextrin (LD), a low-molecular-weight carbohydrate, regarded as a type of short amylose, can form resistant starch when combined with fatty acids. This study investigated the structural properties and in vitro digestion of linear dextrins and their complexes with lauric acid (LA). Four groups of linear dextrins were prepared by pretreating gelatinized high-amylose maize starch (HAMS) with pullulanase followed by gradient ethanol precipitation at concentrations of 0 %, 50 %, 60 %, and 70 % (v/v). The GPC results showed that the weight average molecular weight (Mw) of these linear dextrins were 425.88 kDa, 189.68 kDa, 3.77 kDa and 2.01 kDa, respectively. After linear dextrins were complexed with lauric acid through co-precipitation treatment, the X-ray diffraction data revealed that, except for LD-70-LA, all other complexes formed a V-type structure. The complexing index of the complexes initially increased and then declined with increasing ethanol concentration, reaching a peak value of 41.54 % for LD-50-LA. The LD-0-LA, LD-60-LA and LD-70-LA complexes exhibited weaker anti-digestion properties compared to LD-50-LA, which demonstrated the highest resistant starch content at 52.43 %. This study offers a new approach and application potential for the efficient production of resistant starch. •Debranched high-amylose maize starch was fractionated using gradient ethanol precipitation.•Linear dextrin was characterized using Size-Exclusion Chromatography (SEC).•Formation of single helical conformation was induced by ethanol molecules.•Linear dextrin with different molecular weights displayed distinct complexing properties.•Resistant starch content increased after gradient ethanol precipitation and co-precipitation.