Characterization and Chemical Modification of Amylose Complexes

Effects of chemical and enzymatic modifications on starch-stearic acid complex formation

Debranched unacetylated and acetylated potato starches with two degrees of substitution, 0.041 (low) and 0.078 (high), combined with or without β-amylase hydrolysis were prepared to form soluble and insoluble complexes with stearic acid. The effects of modifications on the complexation, thermal properties, and X-ray patterns of soluble and insoluble complexes were investigated. Acetylation decreased the recovery of insoluble complexes but increased that of soluble complexes. Low acetylated, β-amylase-treated starch had a significantly increased amount of complexed stearic acid (123.1 mg/g) for insoluble complexes; high acetylated, β-amylase-treated starch had the highest complexed stearic acid (61.2 mg/g) for the soluble complexes. The melting temperature of the complexes decreased with acetylation. All β-amylase-treated acetylated complexes displayed the V-type diffraction pattern with peaks at 2θ = 7.4°, 12.9°, and 20°. These results suggest that starch can be modified by acetylation, debranching, and/or β-amylase to produce significant quantities of soluble starch-stearic acid complexes.

Molecular imprinting science and technology: a survey of the literature for the years up to and including 2003

Over 1450 references to original papers, reviews and monographs have herein been collected to document the development of molecular imprinting science and technology from the serendipitous discovery of Polyakov in 1931 to recent attempts to implement and understand the principles underlying the technique and its use in a range of application areas. In the presentation of the assembled references, a section presenting reviews and monographs covering the area is followed by papers dealing with fundamental aspects of molecular imprinting and the development of novel polymer formats. Thereafter, literature describing attempts to apply these polymeric materials to a range of application areas is presented.

Synthesis and characterization of 2,3-di-O-alkylated amyloses: hydrophobic substitution destabilizes helical conformation

Amylose was selectively alkylated in the 2,3-O position of each anhydroglucose unit after trityl protection of the 6-OH groups. Alkyl iodides of varying chain length (C(2), C(5), C(8)) were coupled to amylose, and degrees of substitution (DSs) were varied between 0.3 and 1.8, as assessed by NMR analysis. Increasing amounts of methyl groups per anhydroglucose unit increased solubility in nonaqueous media, while at the same time reducing the ability of modified amylose to form a complex with iodine. The tendency to form inclusion complexes with the surfactant N-dodecyl pyridinium bromide decreased in the order beta-cyclodextrin >> amylose approximately solubilized starch, indicating that the frozen macrocycle of beta-cyclodextrin was the most efficient inclusion host. Introduction of the bulky trityl group abolished the helical amylose conformation, which is not readily reassumed in the presence of hydrophobic substitution of the C2 and C3 positions. These results indicated that a polar outer surface is necessary but not sufficient for the formation of a stable amylose helix.

Influence of physicochemical interactions between amylose and aroma compounds on the retention of aroma in food-like matrices

In food matrices, where starch is often used as a gelling or texturing agent, the occurrence of amylose-aroma complexes and their effect on the release of aroma compounds are difficult to determine. Indeed, thick or gelled systems are known to reduce the diffusion rate of flavor molecules, resulting in an increase of retention. Moreover, interactions between aroma compounds and matrix components might increase the retention of aroma compounds. The complexing behavior of three aroma compounds with amylose was studied by DSC and X-ray diffraction to determine the relative importance of these two factors. Their interaction properties were different: two of them formed complexes, and the third did not. These aroma compounds were added in food matrices containing different starches that induced different textures. Their retention was studied by static headspace analysis. The retention of aroma compounds appeared to depend on the amylose/amylopectin ratio of starch, both from the formation of complexes and by a viscosity effect.

Amphiphilic block copolymer with a molecular recognition site: induction of a novel binding characteristic of amylose by self-assembly of poly(ethylene oxide)-block-amylose in chloroform

Solution properties of amphiphilic methoxy poly(ethylene oxide)-block-amyloses (MPEO-amyloses) in chloroform were investigated by SLS and DLS. The results indicated that MPEO-amyloses dissolved in chloroform containing 2 wt % DMSO by their self-associations. The complexation of MPEO-amylose with methyl orange (MO) was significantly enhanced in the amylose domain of the associate in chloroform. The blue shift of the maximum absorption and strong induced circular dichroism with exciton coupling were observed in the MPEO-amylose MO complex in chloroform. The self-assembly of MPEO-amylose in chloroform shows a unique feature for binding with MO. MPEO-block-amylose is a novel amphiphilic polymer with amylose as a molecular recognition site.

Evidence of starch inclusion complexation with lactones

Starch, in particular the linear amylose, is able to form inclusion complexes with a wide spectrum of ligand molecules, among them flavor compounds. The complexing ability of a homologous series of gamma- and delta-lactones with potato starch was followed by amperometric iodine titration, differential scanning calorimetry, and wide-angle X-ray diffraction measurements. Lactones with a linear chain of a size > or = C(5) form inclusion complexes with starch, whereas lactones with a short linear chain, such as gamma-heptalactone, show poor complexing ability. The thermal stability of starch-lactone complexes increases with increasing chain length of the lactone. In general, lactones induce the formation of V(h) helices. Only delta-decalactone complexes with starch were not definitely identified as V(h) amylose helices. Complexation of starch dispersions with lactones induce turbidity and gelation or phase separation, both phenomena being the result of microphase separation.