Effect of process parameters on slowly digestible and resistant starch content in extrudates

Abstract

A laboratory single-screw Kompaktextruder KE 19/25 was used at speeds 120–140 rpm of the screw with either a 2 : 1 or 3 : 1 compression ratio; the head had a 3 or 4 mm die. The temperature of the head was set at 131–144°C. The applied raw materials were maize grits, and mixtures with wheat starch, pea flour or chemically modified starch. Input mixtures differed in water addition (50 or 100 g water/kg). The highest amount of resistant starch (3.1% per total starch) in extrudate was found for mixture of pea flour and maize grits (with addition of 100 g water/kg of dry mixture), the output(extrudate)/input(mixture) ratio of the resistant starch was 45.8%. The highest SDS content was obtained for the maize grits and addition of 100 g water/kg using a die with a 3 mm diameter and a screw with a 3 : 1 compression ratio; the temperature of the head was approximately 140°C. Transportation rates: screw 140 rpm, dosing 15 rpm.