Cereal Chem 69:528-535   |  VIEW ARTICLE

Physical and Chemical Studies of Taro Starches and Flours.

J. Jane, L. Shen, J. Chen, S. Lim, T. Kasemsuwan, and W. K. Nip. Copyright 1992 by the American Association of Cereal Chemists, Inc. 

Taro (Colocasia esculenta (L.) Schott) flours were prepared from taro corms of Bun-long, Dasheen, Hawaii Red (Lehua), Hawaii White, and Niu'e varieties. Starch contents of the flours varied from 73 to 76% as determined by enzymatic analysis. Starch yields of the flours varied from 51 to 58%. Nitrogen contents varied from 0.33 to 1.35% and from 0.014 to 0.025% in the flours and starches, respectively. Taro starches had irregular, polygonal shapes and small granular sizes. Among the five varieties, Bun-long starch had the smallest average diameter (2.6 micrometers), whereas Dasheen starch had the largest (3.76 micrometers). Amylose contents in these five starch varieties varied from 18 to 22% as determined by iodine affinity and from 19 to 24% as determined by gel permeation chromatography. Molecular sizes of the taro amyloses at the peak of gel permeation chromatography ranged from degree of polymerization (DP) 150 to 550. Branch chain lengths of the taro amylopectin varied from DP 16.8 to 18.4 and from DP 37.2 to 40.5 for short and long branches, respectively. All five starch varieties gave an A-type X-ray diffraction pattern. The taro starches contained 0.23-0.52% lipid and 0.017-0.025% phosphorus. 31P-nuclear magnetic resonance spectra revealed that the phosphorus in the starches was in the form of phosphate monoester derivatives. The onset gelatinization temperatures of the taro flours varied from 72 to 79 C, whereas those of the taro starches ranged from 60 to 74 C. Retrogradations of the starches and the flours, as measured by their enthalpy changes, appeared to be more severe than that of corn starch. Taro starch pastes had significantly higher viscosities than their flour counterparts. Among the varieties, Hawaii Red and Hawaii White starches had the highest peak vicosities, whereas Bun-long starch had the lowest. Both starch and flour pastes set to weak gels.