No abstract

No abstract

The properties of starch separated from potato tubers were studied regarding the following storage temperatures: +20 °C, +8 °C, +4 °C and 0 °C. The study included also potato tubers having been frozen, thawed and refrozen as well as potato tubers before storage. Starch separated from the stored potato tubers showed differences in chemical composition, reducing power, granularity, whiteness and viscosity as well as gelatinization temperatures in comparison with the starch separated from potato tubers before storage. Quantity and direction of the changes within starch properties depended on storage temperatures. The smallest changes in the properties were observed during potato storage at +4 °C and +8 °C.

Starch modification by chemical reaction is widely used to improve the properties of native starch. Modified by citric acid, starch is characterized by specific properties resulting from the presence of citrate residues and as a result of cross-linking starch. The chemicals used for preparing starch citrates are safe for human health and the natural environment compared to the harsh chemicals used for conventional modifications. Starch citrates are traditionally produced by heating starch–citric acid mixtures in semi-dry conditions or by a heat moisture treatment. The conditions of the modification process (roasting temperature, heating time, citric acid dose) and the botanic source or genotype of starch determine the degree of substitution and the properties of the obtained preparations. Changes of starch properties occurring during esterification lead to reduced relative crystallinity, resulting in a decrease in the affinity for water, the gelatinization parameters, and the viscosity of starch citrate. However, one of the most important outcome of the modification is the formation of resistant starch (RS), which has increased resistance to the action of amylolytic enzymes. Currently, new methods for producing starch citrates with improved functional and rheological properties while maintaining the highest possible content of resistant starch are being sought. The article presents an overview of recent studies on the production, properties. And applicability of starch citrates with special attention paid to their role as preparations of resistant starch (RS). The use of citric acid for modification of starch is better for the technology process, while using cross-linking is better than simply using esterification.

The aim of this study was to determine selected properties of extrudates produced from potato starch with the addition of ethyl alcohol. Ethyl alcohol at 5, 10, 15, and 20% concentration was added to potato starch with moisture content of 18 and 23%; the starch was then extruded in single-screw extruder. The extrusion process was carried out in three temperature variants. The resultant extrudates were determined for color, expansion ratio, and mechanical properties. Properties of the extrudates were found to depend on parameters of the extrusion process, moisture content of the extruded sample and ethanol content. Morphological characteristics of the extrudates produced were affected by temperature of the extrusion process, i.e., increasing extrusion temperature resulted in a higher expansion ratio, a lower density, and higher saturation of white color. The extrudates produced from starch with the addition of ethanol were whiter, than those prepared without ethanol. The samples produced with ethanol addition were characterized by a higher number of air spaces and thinner walls, when compared to the those prepared from starch moistened only with water. All mechanical properties were lower in the samples prepared with the addition of ethanol, as compared to the extrudates without its addition.