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

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 mum 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. (C) 2003 Elsevier Science Ltd. All rights reserved.