Combined pretreatment and enzymatic hydrolysis for improved structure and adsorption capacity of red sorghum porous starch

Currently, porous starch production mainly employs single enzymatic hydrolysis, often resulting in low efficiency and uneven pore distribution. In this study, three pretreatment methods were employed to modify red sorghum starch: freeze-thaw (-15 °C for 3 h/60 °C for 15 min), moist-heat annealing (83.33% moisture content at 30 °C for 24 h), and partial pregelatinization (75 °C for 1 min). These pretreatments were combined with composite hydrolysis using a mixture of α-amylase and amyloglucosidase (1:5, w/w). Among these, partial pregelatinization proved to be the most effective method, significantly enhancing the water and oil absorption capacities of the starch to 1.70 ± 0.08 g/g and 2.25 ± 0.16 g/g, respectively. FTIR analysis indicated a reduction in short-range order. SEM revealed a more uniform pore distribution. This study demonstrated that the pretreatment combined with enzymatic hydrolysis improved the porous structure and adsorption capacity of starch, suggesting its potential for applications in bioactive compound encapsulation, drug delivery systems, or heavy metal remediation.