Properties of Low‐substituted Cationic Starch Derivatives Prepared by Different Derivatisation Processes

Abstract

Cationic starch ethers prepared by the chemical reaction of starch with a quaternary ammonium reagent are commercially important derivatives. Cationic potato starch derivatives were produced under pilot‐scale conditions, employing four different principles. Wet cationisation was carried out by the slurry and paste processes, in which the cationic reagent and catalyst are added to the starch. Besides being prepared by these more commonly used processes, cationic starches were also produced by dry cationisation and by adding the cationic reagent during extrusion of starch. The cationic reagent used was 2,3‐epoxypropyltrimethylammonium chloride. Derivatives with three graded degrees of substitution (DS) between 0.03 and 0.12 were prepared by each process. The physical properties of the derivatives were analysed by the following methods: polarised light microscopy, X‐ray scattering, differential scanning calorimetry (DSC), solubility and swelling behaviour, and High‐Performance Size‐Exclusion Chromatography‐Multiangle Laser Light Scattering (HPSEC‐MALLS). The degree of substitution was determined by high resolution 13C‐NMR spectroscopy after hydrolysis with trifluoroacetic acid.The properties of the cationic starch derivatives were highly dependent on the derivatisation method. The granular structure of the starch was not visibly affected by the slurry process. Products from the semi‐dry reaction showed some granular damage, which was particularly evident after suspension of the granules in water. In the paste and extrusion processes, the starch granules were completely destroyed. Swelling temperatures and enthalpies can be determined only for starch derivatives that still retain a granular structure. As a result, samples from the paste and extrusion reactions exhibited no swelling endotherm in DSC. The samples from the slurry process showed a shift in the swelling temperature range towards lower temperature and a decrease in swelling enthalpy both as compared to native potato starch and also with increasing DS. Similar behaviour was found for the samples from the semi‐dry process. The swelling temperature region was comparable to that of the slurry samples for the same DS but the swelling enthalpy was distinctly lower, indicating that the granular structure of the starch was altered far more by the semi‐dry than the slurry process. Swelling in excess water and solubility were affected primarily by the cationisation process, while the influence of DS was of minor importance. The extrusion products had pronounced cold‐water solubility, the semi‐dry products showed increasing cold‐water solubility with increasing DS, the paste products were highly swollen in cold water and the slurry products were insoluble in cold water. All products were soluble in hot water but the state of dissolution was different.The molar mass distributions of the samples were determined after dissolution by pressure cooking. The different derivatisation methods resulted in characteristic molar mass distributions. The average molar mass decreased in the order slurry, semi‐dry‐, paste and extrusion process.

Enzymatic degradation and electrospray tandem mass spectrometry as tools for determining the structure of cationic starches prepared by wet and dry methods

“…Mainly the low molecular mass fraction was detected by HPSEC of the soluble cationic part, which includes primarily the amylose. 16 These different preferences for branching points and end groups over the whole granule in the case of CS-SL and the outer amylose in the dry process are in complete accordance with the B 2 /Y 2 ratios of these samples. The pattern of the MS 2 spectra obtained for the paste-modified cationic starches lies between the slurry-and the dry-modified starches and is similar to that of a CS modified in solution.…”

“…Since the differences in regioselectivity of substitution cannot explain the product pattern of enzymatic degradation, we have to consider relations to amylose and amylopectin. Therefore, we analysed amylopectin and amylose enriched fractions obtained from CS-SL-010 by various procedures as is reported elsewhere by Radosta et al 16 There was a slight but clear difference between the amylose enriched and the amylopectin enriched fractions showing a higher B 2 /Y 2 ratio for the latter (ca. 10) compared to about 4 for the amylose enriched ones (original CS-SL: about 6).…”

“…In the following, the mass spectrometric data and our interpretation will be discussed in context with the properties of the CS samples investigated by Radosta et al 16 In the slurry process, the corn structure is retained and topochemical selectivity is most probable for this heterogeneous procedure. Radosta et al found no decrease in crystallinity, poor cold water solubility, but complete solubility at 95°C for the CS-SL samples independent of DS.…”

“…From HPSEC analysis, it can be concluded that cross-linking had occurred, as was also observed for the other dry process. 16 …”

Effect of cationization on adsorption of silver nanoparticles on cotton surfaces and its antibacterial activity

“…The substitution of hydroxyl group reduces the density of hydrogen bands and thus partially destroys the crystalline structure of cotton fibers. So, the amorphous region is extended for the modified cotton, leading to lower crystallinity Radosta et al 2004;Xie et al 2007;Zhang et al 2007). The effects of these changes on adsorption of silver nanoparticles are discussed in the following sections.…”