title: Isolation and physicochemical characterisation of starch from cocoyam (Colocasia esculenta) grown in Malawi.
abstract: BACKGROUND
  The aim of this study was to determine the physicochemical properties of starches isolated from Malawian cocoyams and compare them with those of cassava and corn starches.
  
  
  RESULTS
  The purity of the isolated starches varied from 851 to 947 g kg(-1) and pH from 4.93 to 6.95. Moisture, ash, protein, fat and amylose contents ranged from 104 to 132, 0.3 to 1.5, 3.5 to 8.4, 0.9 to 1.6, and 111 to 237 g kg(-1), respectively. Cocoyam starches gave higher potassium and phosphorus but lower calcium levels than the other starches. The shape of starch granules varied from spherical to polygonal with cocoyam starches displaying smaller-sized granules than cassava and corn starches. Cocoyam starches gave a higher wavelength of maximum iodine absorption and blue value but lower reducing capacity values than cassava and corn starches. The extent of acid hydrolysis of the starches also differed. Cocoyam starches exhibited amylopectin molecules of higher molecular weights but amylose molecules of lower molecular weights than cassava and corn starches. Cocoyam starches exhibited lower water absorption capacity and swelling power, paste clarity and viscosity but higher solubility, gelatinisation temperatures and retrogradation tendencies than cassava and corn starches.
  
  
  CONCLUSIONS
  The physicochemical properties of native Malawian cocoyam starches vary among the different accessions and differ from those of cassava and corn starches.
authors.affiliation: Plant Sciences Department, University of the Free State, P.O. Box 339, Bloemfontein 9300, South Africa. MwetaDE@ufs.ac.za
authors.forename: Davies E
authors.initials: DE
authors.lastname: Mweta
authors.forename: Maryke T
authors.initials: MT
authors.lastname: Labuschagne
authors.forename: Susanna
authors.initials: S
authors.lastname: Bonnet
authors.forename: Jannie
authors.initials: J
authors.lastname: Swarts
authors.forename: John D K
authors.initials: JD
authors.lastname: Saka
mesh_terms: D000687:Amylopectin / Q000737:chemistry; D000688:Amylose / Q000032:analysis*; D031060:Colocasia / Q000737:chemistry*; D004040:Dietary Carbohydrates / Q000032:analysis; D004041:Dietary Fats / Q000032:analysis; D004044:Dietary Proteins / Q000032:analysis; D005524:Food Technology; D006863:Hydrogen-Ion Concentration; D006868:Hydrolysis; D007455:Iodine / Q000493:pharmacokinetics; D008295:Malawi; D002365:Manihot / Q000737:chemistry; D008970:Molecular Weight; D010316:Particle Size; D035281:Plant Tubers / Q000737:chemistry*; D013213:Starch / Q000737:chemistry* / Q000302:isolation & purification / Q000592:standards; D014131:Trace Elements / Q000032:analysis*; D014867:Water / Q000032:analysis; D003313:Zea mays / Q000737:chemistry
chemical_list: D004040:Dietary Carbohydrates; D004041:Dietary Fats; D004044:Dietary Proteins; D014131:Trace Elements; D014867:Water; D013213:Starch; D000688:Amylose; D000687:Amylopectin; D007455:Iodine