Development of complex investigation of extrudats using acoustic echolocation method

Abstract

The swelling parameters (swelling dynamics – Vd and degree of swelling – V) of rye in a composition with buckwheat were investigated by an acoustic echolocation method. The new provisions production experiment was performed with single and twin screw extruders. The obtained experimental results are presented.
The determined swelling parameters (Vd and V) of extrudates have a good correlation with parameters, analyzed by the instrumental method (expansion index, specific density, mechanical strength of the product and a mean diameter of pores). The experiment performed with both extruders proved that varied buckwheat percentage in rye composition (0 till 40 %) allows us to obtain products with various quality of texture – from snacks to breakfast cereals.
Analysis of solubility and water absorption of non – pores structures of extrudates was done using traditional methods additionally. It proved results obtained by acoustic echolocation method, that during extrusion rye starch granules tend be more degraded and depolymerized in comparison with buckwheat. Rye extrudates like snacks differed by intensive swelling dynamic and their structure in time of 60 seconds was collapsed, taking volume of water about 2,9 ml. Extrudates with buckwheat flour differently from pure rye have swelling property and make more equal structure. Analyzed extrudates with the highest amount of buckwheat flour like breakfast cereals were observed as having a long unbroken not interrupted swelling process, keeping structure during measurement time. This sort of products had a highest degree of swelling (V – 5,4 ml_h2o) and the structure looked most uniform.
This means that acoustic echolocation method gives a complex information both about the texture of end products and the processes during extrusion. This method can be implemented in practice to classify extrudates to different quality grades products.