Preparation of high-quality protein-based extruded pellets expanded by microwave oven

The aim of this work was to study the effects of extrusion barrel temperature (75-140 degrees C) and feed moisture (16-30%) on the production of third-generation snacks expanded by microwave heating. A blend of potato starch (50%), quality protein maize (QPM) (35%), and soybean meal (SM) (15%) was used in the preparation of the snacks. A laboratory single extruder with a 1.5 x 20.0 x 100 mm die-nozzle and a central composite routable experimental design were used. Expansion index (EI) and bulk density (BD) were measured in expanded pellets, viscosity at 83 degrees C (V-83), thermal properties, and relative crystallinity were measured in extruded pellets. El increased and BD decreased when the barrel temperature was increased, while the feed moisture effect was not significant. V-83 increased when feed moisture increased. Extrusion modified the crystalline structures of the pellets and the X-ray data suggests the formation of new structures, probably due to the development of amylose-lipid complexes. The maximum expansion of pellets was found at barrel temperatures of 123-140 degrees C, and feed moisture of 24.5-30%. It is possible to obtain a functional third-generation snack with good expansion characteristics using a microwave oven, and this snack has health benefits due to the addition of QPM and SM.