RESUMO
Sour starch pr "polvilho azedo", a sun-dried fermented cassava starch, is widely known in Brazil as an important cooking ingredient, mainly for biscuit for making. As the process arose from popular knowledge all over the country, it is possible to found different ways of production, nowadays focused in the Southeast and Southern States. The standard of quality of sour starch is not yet clearly defined and empirical quality tools are used in order to manage the production process and to commercialize the product. The economical possibilities qhich arise with the opening of the frontiers for exportation process in South America MERCOSUL strongly recommended further studies in this area. In the present study 31 samples of sour starch were collected in Paraná for investigations concerning sanitary conditions and physical, chemical and functional properties. In almosta all samples it was detected foreign bodies including insects, acarides, rodent's hair and sandy material. The results concerning physical, chemical and functional properties stated medium, minimum and maximum values as well as the range of values at 95 per cent confidence. Compared to the properties of natural cassava starch, overlapping was observed in water content and in water binding capacity. The properties that could be used to discriminate the natural and fermented starch are pH, acidity, solubility of the granules, and specific volume and degree of expansion of the biscuit. Further statistical analysis showed no correlation among the properties, and the results were not useful to discriminate clusters of similarity. As the degree of expansion and specific volume of the biscuit are suitable indicator of quality, both properties can be used to manage the quality of the product and of the process