Synergistic effects of fatty acids and phenolic compounds on enhancing resistant starch formation in rice starch

Starch-lipid complexes are classified as resistant starch (RS) type 5 and their formation can be enhanced through the synergistic action of fatty acids and phenolic compounds. This study investigated the effects of stearic acid, lauric acid, gallic acid, and quercetin on V-amylose complex formation, physicochemical properties, crystallinity, and digestibility of rice starch. The addition of these compounds transformed starch crystallinity from A-type to mixed A- and V-type forms, with relative crystallinity increasing dramatically from 11.6 % in control to 41.4 % in the stearic acid-quercetin complex (R-Ste-Que). V-type diffraction peaks intensified, confirming the formation of stable amylose-lipid-phenolic complexes. SEM showed pronounced surface erosion and cavity development in the starch-fatty acid-phenolic complexes. The highest complexing index (81.87 %) was observed in R-Ste-Que, compared to 0 % in the control. The RS content increased from 1.18 % (control) to 6.56 % in R-Ste-Que, while rapidly digestible starch decreased from 85.22 % to 57.53 %. Differential scanning calorimetry showed the highest enthalpy of amylose-lipid-phenolic complexes at 3.5 J/g in R-Ste-Que, indicating strong V-amylose complex formation. These structural changes highlight the synergistic potential of fatty acids and phenolic compounds to enhance resistant starch formation, offering a promising strategy to develop starch with improved functional and nutritional properties.