Starch-lipid complex formation during extrusion-cooking of model system (rice starch and oleic acid) and real food (rice starch and pistachio nut flour)

The formation of starch-lipid complexes during extrusion-cooking of model system (rice starch and oleic acid) and real food (rice starch and pistachio nut flour) was evaluated. Both formulas were extruded at the same processing conditions (temperature profiles, screw speed, and water feed content). The obtained data showed that in model system and real food, the formation of starch-lipid complexes occurred under different processing conditions. In particular, the highest formation of starch-lipid complexes, that is, the highest melting enthalpy value (Delta H-m = 1.18 J/g), was obtained at the middle values of barrel temperature (100 degrees C) and water feed content (19%) in the model system. Yet, the only processing variable that had a significant effect on the formation of starch-lipid complexes in the real food was barrel temperature. In particular, the highest melting enthalpy of starch-lipid complexes (Delta H-m = 9.28 J/g) was obtained at the highest values of barrel temperature (130 degrees C). These results point out the importance of considering all components present in the raw materials submitted to extrusion-cooking in order to study biopolymer modifications, which occur during processing.