Cereal Chem. 76(5):629-637Structures and properties of starches isolated from different botanical sources were investigated. Apparent and absolute amylose contents of starches were determined by measuring the iodine affinity of defatted whole starch and of fractionated and purified amylopectin. Branch chainlength distributions of amylopectins were analyzed quantitatively using a high-performance anion-exchange chromatography system equipped with a postcolumn enzyme reactor and a pulsed amperometric detector. Thermal and pasting properties were measured using differential scanning calorimetry and a rapid viscoanalyzer, respectively. Absolute amylose contents of most of the starches studied were lower than their apparent amylose contents. This difference correlated with the number of very long branch chains of amylopectin. Studies of amylopectin structures showed that each starch had a distinct branch chain-length distribution profile. Average degrees of polymerization (dp) of amylopectin branch chain length ranged from 18.8 for waxy rice to 30.7 for high-amylose maize VII. Compared with X-ray A-type starches, B-type starches had longer chains. A shoulder of dp 18-21 (chain length of 6.3-7.4 nm) was found in many starches; the chain length of 6.3-7.4 nm was in the proximity of the length of the amylopectin crystalline region. Starches with short average amylopectin branch chain lengths (e.g., waxy rice and sweet rice starch), with large proportions of short branch chains (dp 11-16) relative to the shoulder of dp 18-21 (e.g., wheat and barley starch), and with high starch phosphate monoester content (e.g., potato starch) displayed low gelatinization temperatures. Amylose contents and amylopectin branch chain-length distributions predominantly affected the pasting properties of starch. MATERIALS AND METHODS MaterialsChinese taro, mung bean, waxy rice, sweet rice, green leaf canna, lotus root, water chestnut, and cattail millet starches were isolated in the laboratory as reported by Lim et al (1994). Waxy amaranth I was isolated by the alkaline method (Myers and Fox 1994). Waxy amaranth II and normal glacier barley starch were isolated by a combination of mild alkaline and protease treatments (Radosavljevic et al 1998). Green banana starch was provided by A. R. Bonilla, University of Costa Rica. Waxy maize, amyloseextender (ae) waxy and dull (du) waxy maize starches were gifts of Cerestar, USA (Hammond, IN); potato and wheat starches were purchased from Sigma Chemical Co. (St. Louis, MO);

Scanning electron micrographs of the granules of 54 starches obtained from a wide variety of plant sources, consisting of roots and tubers, grains, maize, peas and beans, fruits and nuts, and small granule starches, are presented as a comparative study of their sizes and morphologies. All micrographs are presented at a magnification of 1500X with the addition of micrographs of 600X for the very large granules and micrographs of 10,000X for the very small granules.

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Information presented here can serve as a guideline for the selection of appropriate conditions for HPP of tuna loins. Our results show that HPP has a potential to replace the highly energy-intensive steam precooking step, which is traditionally required in a canned tuna production process.

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