Characterisation of starches isolated from Arracacha xanthorriza, Canna edulis and Oxalis tuberosa and extracted from potato leaf
Year: 2004
Type: dissertation
Abstract: Starches from Arracacha xanthorriza, Canna edulis and Oxalis tuberosa grown in the Andean region were characterised. All three starches revealed a B-type X-ray diffraction pattern. The amylose content determined by gel permeation chromatography was 4% for A. xanthorriza, 18% for O. tuberosa, and 24% for C. edulis. The complexation ability of the three starches with a surfactant was investigated, and the amylose content was found to be positively correlated with the enthalpy of the complex. The dynamic rheological behaviour of gels made with the three starches was studied in strain-sweep mode. A. xanthorriza starch formed gels which had a stable elastic modulus when stored for three days at 4 ºC. A decrease in pH from 6.5 to 4.0 resulted in a reduction of the elastic modulus for all three starches. The starch content in potato leaves collected at different times on a day and night in July varied between 2% and 13%, with a minimum in early morning and a maximum in late afternoon. Much lower starch content was found in leaves collected in August, when, the morning samples again had the lowest content. Isolated leaf starch granules had either an oval or a round shape with a size smaller than 5 μm. Dimethylsulphoxide-extracted and debranched starches contained small amounts of amylose and a material with intermediate chain length. Unit chains with less than 6 glucose residues were detected in isolated amylopectin. The afternoon samples showed a similar chain length distribution as reported for potato tuber starch, where the populations around DP 19 and DP>35 became significant during the day, whereas the short chains remained basically unchanged. Results from iodine staining indicated that amylose from the afternoon samples had a high proportion of shorter chains. Both leaf and tuber starches seemed to be composed only of amylose and amylopectin, with constant chain length distribution over their molecular weight ranges. The results indicate that the material with molecular weights between the pure amylopectin and amylose is a mixture of the two and not an intermediate material. Purified fragments of isolated leaf starch were analysed with 31P-NMR and no signals corresponding to phosphate monoesters linked to glucose at the C3 and/or C6 positions were detected. The results show that starch in potato leaves does not contain any detectable amounts of phosphate monoesters.
Author: Stalin Santacruz
Language: English
Subfield: Nutrition and Dietetics
Field: Nursing
Domain: Health Sciences
SDG: Zero hunger
Open Access status: green
OpenAlex ID: W1490137423