Annealing is a hydrothermal treatment that changes the structural and functional properties of starches. This study investigates and compares the effects of one-step annealing for 24 and 48 h, respectively, and two-step annealing on the structural, physicochemical, and digestive properties of Castanopsis sclerophylla starch (CaS). Annealing has no effect on CaS morphology, crystalline pattern, and short-range ordered structures. However, annealing decreases the swelling power, solubility, setback, and peak viscosity of CaS and increases its crystallinity and thermal stability. Post annealing, the rapidly digestible starch (RDS) of CaS decreases, the slowly digestible starch (SDS) increases while the resistant starch (RS) content of CaS remains unchanged. Comparing with One-step annealing for 24 h, one-step annealing for 48 h and two-step annealing does not further change the RDS and SDS content of annealed CaS.
In order to explore the application of a new starch source isolated from Castanopsis Sclerophylla , the retrogradation properties and in vitro digestibility of C. Sclerophylla starch (CaS) were investigated for the first time in this study. The Chain-length distribution (CLD) of amylopectin from CaS was characterized. The retrogradation behavior of CaS was measured using rapid viscosity analysis (RVA), rheometry , texture profile analysis (TPA), and differential scanning calorimetry (DSC), and the results compared with those of corn starch (CS). Cas amylopectin displays a lower proportion of short chains (A-chains, 13.31%) and higher proportion of long chains (B3-chains, 31.70%) when compared to corn amylopectin. CaS has a high rate of retrogradation, with higher setback, storage modulus (G′), and lower Tan δ values than CS in short-term retrogradation. CaS gels showed increased hardness and released water from starch gels during storage. Compared with CS, native CaS exhibited higher SDS content and lower RS content and estimated glycemic index (eGI) value. Retrogradation greatly increased the RS content in retrograded CaS and was almost five times higher than that obtained for native CaS after 7 days of storage at 4 °C, whereas it was only slightly higher than that in CS. Furthermore, retrogradation significantly decreased the eGI of CaS, indicating a potential application of CaS in functional food.
Castanopsis sclerophylla is a natural slow-digesting starch resource, and the mechanism by which the endogenous non-starch components slow the digestibility of Castanopsis sclerophylla starch (CaS) remains unclear. In this study, protein, polyphenol, fiber, and pectin were removed from Castanopsis sclerophylla flour (CaF) through enzymatic digestion and water immersion. Their effects on the molecular structure, physicochemical properties, and in vitro digestibility of CaS were systematically investigated. The results showed that the removal of the non-starch components significantly increased the content of rapidly digestible starch but significantly decreased the content of resistant starch from 41.73%. The regulatory priority of each component was in the following order: pectin > fiber ≈ protein > polyphenol. Endogenous non-starch components synergistically inhibited starch digestion through a three-dimensional mechanism: (1) physical barrier—pectin, fiber, and proteins reduced enzyme accessibility by encapsulating starch granules or accelerating their agglomeration, with this effect more prominent in the gelatinized state and masked by the dense crystallinity of non-gelatinized starch; (2) structural stability—these components collectively maintained the short-range ordered structure of starch, reducing enzyme attack sites; (3) physicochemical regulation—pectin enhanced the viscosity of the system through gelation and restricted water mobility, while proteins inhibited starch swelling, which synergistically retarded the process of enzyme diffusion and starch gelatinization. This study reveals that the physical barrier effect of pectin in CaF is the dominant factor affecting starch digestion. Additionally, it provides a theoretical basis and practical guidance for developing low-glycemic index and slow-digesting foods.
危险品化学品经营许可证（带存储）