Abstract
The article presents the results of studies on the model systems of extrudates conducted with a view to determining the function of moisture during the process of forming the structure of starch pastes. There was studied the influence of the moisture content of raw materials on a starch gelatinization point. Studies showed that 15% moisture content in raw materials is sufficient for its constituent phase - starch gelatinization, as well as for the transition of the whole mass to a fluid-viscous state. Further increase in the moisture content is accompanied by a decrease in a gelatinization point. In order to study the influence of moisture on the formation of a porous structure of extrudates, we studied the relationship between the different-type starch pastes and the degree of its transparency and its embrittlement temperature. It has been found that during the process of thermal and mechanical impacts, there occurs the process of the formation of a structure of starch pastes, in particular, samples with the different moisture contents can have an amorphous or crystalline structure. There has been established the relationship between the moisture content of raw materials on the modulus of elasticity of starch pastes based on them. The modulus of elasticity of samples was determined one hour (cooling time to room temperature) and one week after obtaining the starch paste. The above studies showed that minimal physico-chemical and mechanical transformations occur in starch pastes, which are in an amorphous state, that is, in the conditions of a low moisture content. We have established that the moisture content of raw materials, on the one hand, ensures the transition of a high-dispersive phase to a fluid state, or implementing the ex process of extrusion, and on the other hand, influences on the formation of a porous structure in the extrudates.
Highlights
The process of thermoplastic extrusion in the food industry is a new innovative technology, which is distinguished by high productivity and efficiency
It is known that the maximum temperature required for the process of thermoplastic extrusion and the moisture content of processing raw materials have a particular impact on the quality of extrudates, as well as on the physicochemical and structural characteristics of starch paste
Figure shows that in samples with a moisture content below 10%, the embrittlement temperature is higher than 20 °C, the increase in a moisture content of starch pastes results in a lower embrittlement temperature, for example in the case of 25 – 30% moisture content, the embrittlement temperature is -7 to (-11 °C), This means that moisture plays the role of a plasticizer in such a system, while the increase in its amount leads to increasing fluidity micromolecular chains
Summary
The process of thermoplastic extrusion in the food industry is a new innovative technology, which is distinguished by high productivity and efficiency. Hydro-thermo-mechanical impact resulting in physicochemical changes in them, so starch gelatinization and denaturation of proteins occur in extruding raw materials during the process of thermoplastic extrusion (Litviak, 2013; Karpov, 2000; Van Lengerich, Meuser and Pfaller, 1989).
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