Béatrice Conde-Petit

Characterization of amylose—flavour complexes by DSC and X-ray diffraction

Abstract Amylose is able to form complexes with a variety of ligands such as fatty acids, emulsifiers and flavour substances. The complex-forming molecules induce the formation of single amylose helices (V amylose). Starch complexation with flavour molecules is one of the mechanisms of flavour retention in starch-containing food systems. Furthermore, the formation of starch—flavour complexes modifies the texture of low-concentration starch systems. In the present investigation, starch—flavour complexes were prepared by combining aqueous potato starch dispersion (2 g/100 g) with decanal and (−)fenchone respectively. The water-insoluble ligands were introduced with the aid of lecithin as non-complexing emulsifier. Flavour molecules other than decanal and (−)fenchone were added directly or dissolved in ethanol. DSC measurements and X-ray powder diffraction were carried out on freeze-dried samples. X-ray diffraction clearly showed the pattern of V amylose, indicating the formation of complexes with different crystalline structures. Endothermic transitions as shown by DSC correlated with the melting of the crystalline amylose-flavour complexes. No correlation was found between the melting temperature measured by DSC and the crystallinity determined by X-ray diffraction.

Comparative characterisation of aqueous starch dispersions by light microscopy, rheometry and iodine binding behaviour

Aqueous potato, wheat and pea starch dispersions (2 g dry Starch/100 g dispersion) were prepared at different time-temperature conditions and characterised by light microscopy of stained cryo-sections, amperometric iodine titration and rheometry. Depending on the gelatinisation conditions and the type of starch, a broad range of microstructures was obtained ranging from limited swelling to complete disintegration of starch granules. The swelling was accompanied by leaching of amylose from the granules and accumulation of amylose in the centre of the granules. The iodine binding capacity of the starch systems was related to the extent of swelling and solubilisation of starch and is therefore an appropriate indicator to follow the gelatinisation process. The flow behaviour was also sensitive to differences in the microstructure. The combination of light microscopy, iodometry and rheology successfully allowed the extensive characterisation of the supramolecular structure of low concentration starch systems.

Structural features of starch–lactone inclusion complexes in aqueous potato starch dispersions: the role of amylose and amylopectin

Abstract Starch, in particular the linear amylose, is able to form inclusion complexes with a wide spectrum of ligand molecules, among them flavor compounds such as lactones. The structural properties of potato starch dispersions with lactones were followed with oscillatory measurements, amperometric iodine titration, X-ray diffraction measurements, and light microscopy. The complexation of starch influences the structural properties of starch dispersions at different length scales. At the macroscopic level, the unfavourable interaction of amylose–lactone complexes with water promotes gelation or phase separation, and amylose–lactone complexation leads to spherulitic crystallization. Amylopectin–lactone interactions are thought to contribute to the long-term behavior of starch dispersions. Thereby, the colloidal properties of starch dispersion and spherulite morphology are determined by the type of lactone and the kinetics of starch complexation.

Complexation induced changes of rheological properties of starch systems at different moisture levels

Starch, especially the linear amylose fraction, is able to form helical inclusion compounds or complexes with molecules like flavor compounds, fatty acids, and emulsifiers. The effects of starch complexation on rheological properties were studied (a) in aqueous dispersions of 1%–4% starch content, (b) in high‐concentration gels of 40% starch content, and (c) in extrusion cooked low moisture starch blends. Complexation was followed by iodine binding capacity of starch and by differential scanning calorimetry. Rheological characterization was based on dynamic and steady shear measurements and on uniaxial force deformation tests. At low starch concentrations, the addition of complexing emulsifiers and flavor compounds induced gelation, provided that enough amylose was solubilized and swollen granules were present. Likewise, freshly prepared high‐concentration starch gels with the addition of complexing ligands exhibited higher moduli of deformability than control samples without additives. The sequence of mo...

Rheology and structure of amylopectin potato starch dispersions without and with emulsifier addition

Low-concentrated aqueous dispersions of amylopectin potato starch were characterised by light microscopy and rheological measurements. With increasing heat treatment the granular structure was more and more disintegrated. The dispersions were of transparent appearance, exhibited a shear-thinning behaviour, and showed a time-dependent increase in viscosity. The addition of calcium stearoyl-lactyl-2-lactylate (CSL) and glyceryl monostearate (GMS), respectively, to low concentration amylopectin potato starch dispersion resulted in the formation of soft gels. Emulsifier-emulsifier or emulsifier-starch interactions promote the development of a weak network structure. It is also conceivable that side chains of the amylopectin in amylose-free potato starch are able to form complexes. Results obtained by iodine colorimetry gave some evidence of a possible complex formation between amylopectin potato starch and CSL.

Influence of starch flavour interactions on rheological properties of low concentration starch systems

Abstract Interactions between starch and the complex forming flavour substances decanal and (—)fenchone were studied in low concentration starch systems. Rheological changes were determined with dynamic measurements, the formation of complexes by measuring the iodine binding capacity of starch and by X-ray diffractometry. Decanal and (—)fenchone led to the formation of amylose helices with 6 and 7 d -glycosyl units per turn, respectively, and induced the gelation of low concentration starch systems.

Influence of xanthan on the rheological properties of aqueous starch-emulsifier systems

Abstract Interactions between potato starch and complex-forming emulsifiers in the presence of xanthan, and their consequences on the rheological properties, were investigated. The aqueous starch-xanthan-emulsifier systems were prepared by mixing the separately dispersed components or by heating the components together. The amount of leached amy lose and the formation of starch-emulsifier complexes were determined by amperometric iodine titration. The viscoelasticity was measured with small-deformation oscillatory tests. The results show that while the incompatibility between starch and xanthan does not affect the formation of starch-emulsifier complexes, it does hinder the gelation process induced by starch complexation and reduce the firmness of the resulting gels. The combination of starch with small amounts of an incompatible biopolymer like xanthan and a complex-forming emulsifier allows the generation of different gel structures.

Gelation of low concentration starch systems induced by starch emulsifier complexation

Abstract Starch-emulsifier interactions were studied in low concentration model starch dispersions prepared with glycerol monostearate (GMS) or lecithin (LEC). The degree of complex formation was determined by measuring the iodine binding capacity of starch; the rheological properties were investigated with dynamic and steady shear measurements. GMS formed insoluble starch inclusion complexes inducing starch gelation in 2% starch dispersions, provided that enough amylose was solubilized and swollen starch granules were present. LEC did not form complexes and failed to induce starch gelation.

Chapter 8:Self-Assembly of Starch Spherulites as Induced by Inclusion Complexation with Small Ligands

Starch is synthesized in higher plants in the form of partly crystalline granules with different morphologies and sizes between 1 and 100 μm. The linear amylose and the branched amylopectin are the starch polymers, and most common starches are composed of 25% amylose and 75% amylopectin. The formati...

Phase Separation of Aqueous Starch/Galactomannan Systems: Influence of β-Lactoglobulin Addition

ABSTRACT Phase behaviour (at 25° and 60°), kinetics of phase separation and rheological properties of aqueous amylopectin/galactomannan mixtures were investigated. The influence of β-lactoglobulin addition on the aforementioned parameters was studied. Binodals typical of this system are located towards the concentration axis of the lower molecular weight polysaccharide, i.e. amylopectin. The addition of 1% (w/w) β-lactoglobulin to the amylopectin/galactomannan system resulted in a shift of the binodal towards lower polysaccharide concentrations. The β-lactoglobulin was partitioned equally between the two polysaccharide phases. Phase separation kinetics in the bulk of a 5 ml sample determined from Vertical Scan Near Infrared Analysis indicate a completion of phase separation after 8 hours.