Amylose contents, rheological properties and gelatinization kinetics of yam (Dioscorea alata) and cassava (Manihot utilissima) starches
2004
Freitas, R.A. | Paula, R.C. | Feitosa, J.P.A. | Rocha, S. | Sierakowski, M.R.
After defatting yam and cassava starches have amylose contents of 36.2 and 24.2%, respectively. Suspensions of these starches in water were analysed, in an oscillatory rheometer, using a heating rate of 4.0 °C min-1, deformation of 1% and a frequency of 1 Hz, the initial temperatures of gelatinization being 71 and 62 °C for yam and cassava, respectively. A gelatinization study was also carried out by differential scanning calorimetry with different heating rates (2.5, 3.0, 4.0 and 5.0 °C min-1), to give, by the Arrhenius equation, the activation Energy (Ea) of the process. Yam starch showed a more energetic gelatinization process of when compared to cassava starch and also had a lower rate constant (s-1), indicating a relatively slow gelatinization process of at higher temperatures. Yam gels formed by autoclaving a suspension (50 g l-1) showed after 24 h of refrigeration, a stronger structure than for a cassava gel.
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