Preparation and properties of pregelatinized cassava (Manihot esculenta. Crantz) and jicama (Pachyrhizus erosus) starches using ohmic heating.

摘要

Pregelatinized starches are used in food systems as stabilizing additives, moisture retainers and thickeners. Drum driers and extrusion processes used in the industry for preparing pregelatinized starches cause severe degradation of starch granules, increasing the amount of soluble solids. In this study, the use of an ohmic heating process, in which an electric current is passed through the material to generate heat, to minimize loss of solids and obtain an adequate degree of gelatinization in jicama (Pachyrhizus erosus) and cassava (Manihot esculenta) starch obtained in Mexico, was evaluated. Ohmic heating caused greater effects of gelatinization (P?0.05) with high voltage (123 V) and short processing time (10 minutes). In the case of jicama starch, the water absorption index (50 degrees C) ranged from 3.2 to 4.7% and the water solubility index (50 degrees C) from 1.2 to 2.2%. For cassava starch, the results were 3.7 to 5.4% and 3.2 to 6.1%, respectively. Analysis of viscosity and thermal properties indicated that treatments with maximum voltage and longer processing times gelatinized 70.0% of the native jicama starch and 39.1% of the cassava starch. The starches obtained showed different functional properties with diverse degrees of gelatinization that may be used in the food industry..