The Construction of Sodium Alginate/Carboxymethyl Chitosan Microcapsules as the Physical Barrier to Reduce Corn Starch Digestion

To enhance the resistant starch (RS) content of corn starch, in this work, carboxymethyl chitosan/corn starch/sodium alginate microcapsules (CMCS/CS/SA) with varying concentrations of SA in a citric acid (CA) solution were designed. As the SA concentration increased from 0.5% to 2%, the swelling of the CMCS/CS/SA microcapsule decreased from 15.28 ± 0.21 g/g to 3.76 ± 0.66 g/g at 95 °C. Comparatively, the onset, peak, and conclusion temperatures (T_o, T_p, and T_c) of CMCS/CS/SA microcapsules were higher than those of unencapsulated CS, indicating that the dense network structure of microcapsules reduced the contact area between starch granules and water, thereby improving thermal stability. With increasing SA concentration, the intact and dense network of CMCS/CS/SA microcapsules remained less damaged after 120 min of digestion, suggesting that the microcapsules with a high SA concentration provided better protection to starch, thereby reducing amylase digestibility. Moreover, as the SA concentration increased from 0.5% to 2%, the RS content of the microcapsules during in vitro digestion rose from 42.37 ± 0.07% to 57.65 ± 0.45%, attributed to the blocking effect of the microcapsule shell on amylase activity. This study offers innovative insights and strategies to develop functional starch with glycemic control properties, holding significant scientific and practical value in preventing diseases associated with abnormal glucose metabolism.