Método para determinação de volume específico como padrão de qualidade do polvilho azedo e sucedâneos/Method for the determination of specific volume as a quality standard for fermented cassava starch and substitutes

The objective was to establish a method for the determination of the expansion of cassava starch and substitutes as a quality standard. Three types of cassava starch were evaluated: Fermented Cassava Starch, Expandex® and Native Starch. The samples were put directly into silicone or metal polytetrafluoroethylene moulds and baked under controlled conditions of temperature (200 or 250 °C) and time (20 or 25 minutes). The proposed method was evaluated by the repeatability of the specific volume (volume ratio:mass) and the results compared with those obtained by the traditional method, in which the ingredients were handled in boiling water, moulded into balls by hand, and subsequently baked in greased aluminium baking pans under the same conditions. The selection of the best method took into account the highest values for specific volume (cm3 g-1) and the least variations between repetitions. For the silicon mould, the best results were obtained under the conditions of 200 °C and 25 min (8.89 cm3 g-1 with 1.46% variability), which provided pastas sufficiently resistant to handling to allow for the taking of measurements. For the polytetrafluoroethylene moulds, the best conditions were 200 °C for 20 minutes (8.16 cm3 g-1 with 7.59% variability). The sample Expandex® showed the same response as cassava starch to the variables of oven temperature and baking time, but showed higher values. The presence of residual intact granules showed that gelatinization of the starch was not completed under the baking conditions used. The proposed method showed ease of handling and the time required was just that necessary to knead the dough with water and bake it.