Study on formation of starch–lipid complexes during extrusion-cooking of almond flour

Abstract

A blend containing almond and wheat flours (about 1:2.5, dry basis) was extruded through a co-rotating twin-screw extruder with a screw diameter of 25 mm. The effects of barrel temperature (61.72–118.28 °C) and feed moisture (21.17–26.83%) on starch–lipid complex formation (X-ray diffraction, melting enthalpy, and complexing index) as well as on fat loss (which occurs during extrusion processing), break strength, deformability and expansion index of extrudates were investigated using response surface methodology (RSM). The only variable that had a significant influence on the formation of starch–lipid complexes was feed moisture (the high values of melting enthalpy and complexing index, i.e. 3.67 J/g and 94.34%, respectively, were obtained with the smallest value of feed moisture, i.e. 21.17%). The highest fat loss and the hardest texture of extrudates were obtained at the highest values of barrel temperature and feed moisture (118.28 °C and 26.83%, respectively).