|Li, Li - IOWA STATE UNIVERSITY|
|Jay-Lin, Jane - IOWA STATE UNIVERSITY|
Submitted to: Corn Utilization Conference Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: March 20, 2004
Publication Date: June 7, 2004
Citation: Li, L., Blanco, M.H., Jay-Lin, J. 2004. Physicochemical properties of maize starch during endosperm development. Corn Utilization Conference Proceedings. P. 39. Technical Abstract: Starches were isolated from maize (B73) on 0, 5, 6, 8, 10, 12, 14, 20 and 30 days after pollination (DAP), and the physicochemical changes of maize starch investigated. Starch content in the kernel was 7.8% on dry basis on 0 DAP, and increased rapidly from 22.8% up to 83% at 14 days and 30DAP respectively. Amylose content increased from 20.2% up to 27.1% at 0 and 30DAP respectively. Scanning electron micrograph showed that starch granular sizes were small and similar (diameter 2-4m) from 0 to 12DAP, increasing to 4-8m at 14 DAP, up to 10-15m at 20-30 DAP. Amylopectin molecular weight determined by using HPSEC equipped with MALLS detector showed that starches harvested from 5 to 12DAP had lower molecular weight than those harvested after 12DAP. The onset gelatinization temperature of starch isolated on 0DAP (56.3C) was about 5 degrees lower than that of 5 to 12DAP (61.3-62.4C), and increased up to 68.8C at 30 DAP. Starch retrogradation rate increased from 31.6% (0DAP) to 50.1% (30DAP). The branch chain-length distributions of amylopectin analyzed by HPAEC showed that the very short chains (DP6-12) decreased with the development of endosperm, whereas the chains of DP 13-24 increased. Branch chain length of amylopectins changed with the maturation of maize increasing the onset of gelatinization temperature. Starch harvested on 0DAP showed higher amylose content, larger amylopectin molecular weight, and much lower onset gelatinization temperature than starch harvested on 5DAP. These results indicated that the starch present in the kernel before pollination might have a different biosynthesis system from endosperm starch.