Polvilho azedo tradicional obtido com alteração na etapa de secagem solar

Abstract

The sour cassava starch is a product derived from cassava and, after going through the processes of natural fermentation and solar drying, acquires a property of differentiated expansion, that allows its use in expanded baked products. The process of solar drying is carried out in the open areas, without protection, and contamination by dirtiness and insects from environment can occur. Thus, the aim of this work was to obtain sour cassava starch of high quality in a controlled process, including the use of a low cost solar dryer that takes advantage of thermal energy, ultraviolet radiation, and prevents contamination and maintains the original characteristics of the product. The sour cassava starches were obtained from the native cassava starch, varying the type of drying. The samples were evaluated by chemical, microbiological and microscopic composition, as well as presence of physical contaminants. Expansion, thermal, pasting, structural, and technological properties were also evaluated. In addition, cassava starch biscuits were prepared and sensorially compared with commercial samples. The use of the solar dryer in the drying of the sour cassava starch has provided a faster drying and lower moisture (9.9 and 9.7%) than the control (11.6 and 11.5%). The specific volumes obtained for the samples dried in the sun and in the solar dryer ranged from 4.2 to 4.9 mL g-1 , showing that the solar dryer obtained products with the same expansion capacity as the control (4.6 mL g-1 ). These values are considered of small expansion and can be explained by the absense of lactic acid in the samples. The solar dryer minimized the contamination, being found insect fragments and sand-earth material, which can be avoided using protection screens and drying process in places without transit of vehicles. All the samples have presented high total carbohydrate content (99.6%). The pH of the native starch was 4.90, whereas fermented starch from 4.52 to 4.63, due to the action of lactic acid bacteria during fermentation. The granules of the fermented starches have presented slight erosions on their surface, probably due to the action of amylolytic enzymes. No significant differences (p>0,05) were found between the samples in terms of color, amylose content, syneresis, solubility, swelling power, carbonyl and carboxyl content and structural properties. The oxidation resulted in more transparent pastes for the fermented starches than native starch. Differential dyeing has suggested a lower presence of carboxyl groups in the native starch, with the exception of a dry sample in the solar dryer. X-ray diffraction analysis has showed the A-type pattern. Thermal analysis resulted in higher temperature values and enthalpy change for sour cassava starch. The pasting properties have showed a reduction in the viscosity peak at neutral pH. The cassava starch biscuit made with sour cassava starch obtained by drying in the solar dryer, although presenting the smallest expansion in relation to the other biscuits produced with commercial grade sour cassava starch, presented desirable sensory characteristics.