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A comparative study of edible canna (Canna edulis) starch from different cultivars. Part I. Chemical composition and physicochemical properties

Abstract
The chemical composition and physicochemical properties of starches isolated from three cultivars (Japanese-green, Thai-green and Thai-purple) of edible canna rhizomes were studied. Scanning electron microscopy investigations showed that the starch granules from all cultivars of canna were oval-shaped granules with smooth surfaces and were around 10–100 μm in sizes. Proximate composition studies showed that the protein content in the canna samples varied between 0.069 and 0.078%, lipid between 0.014 and 0.019% and ash between 0.25 and 0.33%. All canna starches contained considerably high phosphorus (371–399 ppm), followed by calcium (113–154 ppm) and potassium (35–61 ppm). The absolute amylose content ranged from 19 to 25%. All three starches displayed a B-type X-ray diffraction pattern. The viscograms of canna starches determined by Rapid Visco Analyzer showed that Thai-green and Japanese-green starches paste were quite stable during cooking and had high setback. The enthalpy for gelatinization and dissociation of retrograded canna starches, investigated using differential scanning calorimeter, were 17.6–18.4 and 12.3–15.0 J/g of starch, respectively. The results obtained from freeze-thaw stability and light transmittance measurements indicated that all canna starches had a high tendency for retrogradation.

Keywords
Canna edulis; Edible canna starch; Cultivar; Physicochemical properties; Composition

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