Physicochemical properties of normal and waxy Job's Tears (Coix lachryma-jobi L.) starch

Physicochemical properties of starches from eight coix (Coh lachrymajobi L. ) accessions were investigated. There was considerable variation in most me asured traits, generally corresponding to the separation into waxy and norm al amylose types. The amylose contents of five normal coix ranged from 15.9 to 25.8%, and those of three waxy coix were 0.7-1.1%. Swelling power of wa xy coix starches varied between 28.6 and 41.0 g/g, generally higher than wa xy maize. Normal coix starches had significantly higher gelatinization peak temperature (T-p) than the normal maize, 71.9-75.5 degrees C. The T-p of w axy coix starches was 71.1-71.4 degrees C, similar to waxy maize. Rapid Vis co-Analyzer (RVA) pasting profiles of normal coix showed little variation a nd closely matched the normal maize starch profile. Pasting profiles of wax y coix showed more variation and had lower peak viscosities than waxy maize starch. Waxy coix starches formed very weak gels, while the gel hardness o f normal coix starches was 11.4-31.1 g. Amylose content was the main factor controlling differences in starch properties of the coix starches.