Molecular structures and some properties of starches from propagules of mangrove species

Molecular structures and some properties of starches from propagules of mangrove species, Rhizophora stylosa Griff. (Rs), Kandelia candel (L.) Druce (Kc), and Bruguiera gymnorrhiza (L.) Lamk. (Bg), were examined. Starch content (dry basis, %) of mature propagules was 26.8-33.9. The Rs, Kc and Bg starch showed Ca, Cb and Cc crystalline type, respectively. Pasting properties differed greatly by source especially for Kc starch having the highest peak-viscosity and similar to 10 degreesC lower pasting temperature (68.9 degreesC). Actual amylose content (%) was 26.3, 24.5 and 22.3 for Rs, Kc and Bg starch. Bg amylose showed number-average degree of polymerization (DPn, determined by a fluorescent labeling method) of 840 while Rs and Kc amyloses showed larger DPn, 2620 and 2200. The mangrove amyloses contained highly branched molecules (average number of chains, 13.8-16.8) with varying proportion (14-57% by mole). DPn of Rs, Kc and Bg amylopectin was 15,700, 15,900 and 11,000, respectively. The Rs amylopectin was characteristic in that the molecular species having medium size (DPn 11,900) predominated (50% by mole). Number-average chain length (2022) and phosphorus content (126-242 ppm) of the amylopectins were comparable to those of sweet potato amylopectins. The molar ratio of unit chains, (A + B-1)/(B-2 + B-3), was considerably different, 5.8-8.5, and the ratios indicated sparse branching of the amylopectins. (C) 2004 Elsevier B.V. All rights reserved.