Understanding the fine structure of intermediate materials of maize starches

- Molecular fine structure of starch intermediate material (IM) was further disclosed.
- IM had longer B- and BL-chains than did amylopectin.
- IM had a higher average length of total internal chains than did amylopectin.
- IM had a similar average length of external chains to that of amylopectin.
- A higher amylose content increased the amount of relatively-long chains in IM.

Here we concern the molecular fine structure of intermediate material (IM) fraction in regular maize starch (RMS) and Starpro 40 maize starch (S40). IM had a branching degree and a molar mass (Mw) somewhere between amylopectin (AP) and amylose (AM). Compared with AP, IM had more extra-long (Fr I) and long (Fr II) chains and fb3-chains (degree of polymerization (DP) > 36), with a higher average chain length (CL). Also, IM contained less A-chains but more B-chains (both BS-chains with DP 3-25 and BL-chains with DP ≥ 26), accompanied by longer B- and BL-chains, total internal chains (TICL) and average internal chains (ICL), and a similar average external chain length (ECL). Furthermore, relative to RMS-IM, the IM of S40 (with higher apparent amylose content than RMS) showed increases in relatively-long chains, e.g., Fr II, fb3-chains and BL-chains, but reductions in Mw, relatively-short chains (those with DP 6-12, etc.).