Effect of processing conditions and concentration of water and milk suspensions on the dynamic viscosity of corn-cranberry gluten-free instant gruels

A b s t r a c t. Selecting the parameters of the extrusion-cooking process makes it possible to produce various types of extrudates with a certain density, expansion, water absorption capacity, stickiness, etc. Porridges and gruels for children are products in a loose form, obtained from rice, corn, rye, oat, barley, buckwheat, millet or wheat flour, that can be produced with conventional drumdrying but also with the application of extrusion-cooking. The aim of the study was to evaluate the effect of dried cranberries addition level and processing conditions of instant corn-cranberry gruels on the dynamic viscosity of solutions with various concentrations and liquid medium used. The results showed that increasing content of cranberries in the recipe resulted in an increase of the dynamic viscosity value of extruded gruels suspensions. Increasing the screw speed during processing caused a decrease in the dynamic viscosity of extruded gruels in the case of aqueous suspensions tested at 40°C. Increasing viscosity along with the increase of screw speed was observed in all milk suspensions. Increasing the temperature of water and milk suspensions caused a decrease in the dynamic viscosity values of extruded corn-cranberry instant gruels. Higher values of dynamic viscosity were observed in the case of suspensions prepared with milk. K e y w o r d s: extrusion-cooking, corn, cranberry, gluten-free, dynamic viscosity