Submitted to: Starch/Starke
Publication Type: Peer reviewed journal
Publication Acceptance Date: 1/30/2007
Publication Date: 3/28/2007
Citation: Stevenson, D.G., Jane, J., Inglett, G.E. 2007. Characterisation of jicama (mexican potato)(Pachyrhizus erosus L. Urban) starch from taproots grown in USA and Mexico. Starch/Starke. 59(3-4):132-140. Interpretive Summary: Starch characteristics were studied from jícama roots cultivated in Texas and two locations in Mexico. Jícama starch had absolute amylose content of 24%, short amylopectin average branch chain-length and the temperature that starch started melting was extremely low relative to most other starches. Paste viscosity was very high relative to other starches, but starch paste was degraded substantially during heat and shear conditions. Jícama starch could have advantages over other unmodified starches in industrial applications where thickening is required but heat is minimized to avoid adverse reactions. Knowledge from this study provides starch industry with broader range of applications and insight into how starch structure influences functional properties.
Technical Abstract: Characteristics of starch extracted from roots of jícama (Pachyrhizus erosus L. Urban) cultivated in Texas and two locations in Mexico were studied. Jícama starch granules were spherical or polygonal with diameters ranging from 1-13 micrometers. Jícama starch exhibited A-type X-ray diffraction pattern, an apparent amylose content of 28.1% and absolute amylose content of 23.6%. Jícama amylopectin weight-average molecular weight (Mw) was 3.9 x 108 and gyration radius (Rz) was 363 [nm]. Average amylopectin branch chain-length was short (DP 22.7). Onset gelatinization temperatures was very low (52.0 deg C and enthalpy change was 15.1 [J/g]. Amylose-lipid thermal transition was not observed. Peak (282 [RVU]), final (221 [RVU]) and breakdown (137 [RVU]) viscosity of 8% jícama starch paste was high relative to other starches and pasting temperature was 72.3 deg C. Starch characteristics were similar in all three growing locations except for Mw, Rz and pasting properties. High paste viscosities and low gelatinization temperature could give jícama starch some advantages in industrial applications.