Study of starch-lipid complexes in model system and real food produced using extrusion-cooking technology T. De Pilli a, ⁎, A. Derossi a , R.A. Talja b , K. Jouppila c , C. Severini a a Department of Food Science, Faculty of Agriculture, University of Foggia, Via Napoli 25, 71100 Foggia, Italy b KCL, P.O. Box 70, FI-02151 Espoo, Finland c Department of Food and Environmental Sciences, P.O. Box 66 (Agnes Sjöbergin katu 2), FI-00014 University of Helsinki, Finland abstract article info Article history: Received 26 February 2011 Accepted 20 July 2011 Editor Proof Receive Date 17 August 2011 Keywords: Starch-lipid complexes Pistachio nut flour Starch Oleic acid Fat loss Extrusion cooking The formation of starch-lipid complexes during extrusion of model system (rice starch added with oleic acid) and real food (rice starch added with pistachio nut flour) was evaluated. Both formulas were extruded at the same processing conditions (temperature profiles, screw speed and water feed content). The formation of starch-lipid complexes in real food, is strongly dependent on water feed content. In fact, at barrel temperature of 128 °C, the highest melting enthalpy of real food (6.7 J/g) was obtained only at 21% of water feed content whereas in the model system it was obtained both at 16 and 21%. These results point out the importance to consider all components present in the extruded food in order to study biopolymers modifications that occur during processing. Industrial relevance: Additions of lipids alter the physical and chemical properties of starchy foods. The changes brought about by them in starchy foods have been attributed to the formation of complexes between amylose and lipids. These changes in the functionality of starch are of interest to the food industry and for human nutrition. Lipid complexation with starch is a very important reaction in extrusion cooking that affects structure formation and texture of the extruded products. Most studies on the starch-lipid complex formation during extrusion of model systems like starch and free fatty acids have been carried out, instead very little is known about starch-lipid complex formation during extrusion of flour blends containing fatty meal. This paper points out the importance to consider all components present in the food extruded in order to study biopolymers modifications that occur during processing. For this reason it is very important to use model systems that are not very different to real food and anyhow it would be advisable to verify the obtained results on real food, above all when a relation between macromolecular modifications and quality characteristics of extruded products would be studied. © 2011 Elsevier Ltd. All rights reserved. 1. Introduction Addition of fatty acids alters the physical and chemical properties of starchy foods (Singh, Cairns, Morris, & Smith, 1998a). The changes brought about by them in starchy foods have been attributed to the formation of complexes between amylose and lipids. Lipids have been reported to form inclusion compounds with amylose, with the hydrocarbon portion of the lipid located within the helical cavity of amylose (Kaur & Singh, 2000). Since these changes in the functionality of starch are of interest to the food industry and for human nutrition, starch-lipid complexes have been studied extensively using various methods. For example, crystallinity has been examined by X-ray diffraction (XRD), and differential scanning calorimetry has been used to analyze melting- transition characteristics and stability of the complexes (Nebesny, Rosicka, & Tkaczk, 2005). Among food processing, extrusion-cooking is usually a versatile and very efficient technology. Lipid complexation with starch is a very important reaction in extrusion cooking that affects structure formation and texture of the extruded products. Nevertheless, most of these papers studied the starch-lipid complex formation during extrusion of model systems like starch and free fatty acids have been carried out, instead very little is known about starch-lipid complex formation during extrusion of flour blends containing fatty meal. In a previous work, De Pilli et al. (2008) investigated the formation of starch-lipid complexes during extrusion-cooking of a blend contain- ing 25% almond and 75% wheat flour at different operating conditions (barrel temperature and water feed content) by X-ray diffraction, DSC and complexing index. Wheat flour, which was considered as reference material, was extruded at the same processing conditions. Nevertheless, the authors comparing their results with those reported in previous literature, relating to starch or flour added with fat free acids, did not consider that the thermal conditions at which occurs the Innovative Food Science and Emerging Technologies 12 (2011) 610–616 ⁎ Corresponding author. Tel.:+39 881 589245; fax + 39 881 589308. E-mail address: t.depilli@unifg.it (T. De Pilli). 1466-8564/$ – see front matter © 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.ifset.2011.07.011 Contents lists available at ScienceDirect Innovative Food Science and Emerging Technologies journal homepage: www.elsevier.com/locate/ifset