Modification and characterisation by ESCA, of starch and related polymers

Abstract

Starch was isolated from soft wheat cultivar (Galahad), by wet fractionation. Electron Spectroscopy for Chemical Analysis (ESCA) was used to examine the surface composition of native and chlorine treated starches, before and after secondary treatments with Pronase enzyme and methanol, which remove respectively, lipid and protein from the starch granule surface. Analysis showed the presence of carbon, oxygen, nitrogen, sulphur and phosphorus in native starch, with a lower C/0 elemental ratio than the theoretical value. This was attributed to the presence of lipid, protein and extraneous hydrocarbon, and confirmed by the analysis of native starch modified by the secondary treatments. Chlorine treatment was found to induce surface oxidation of native starch samples. Covalently bound chlorine was detected which was thought to bind to the lipid and protein residues in preference to the carbohydrate component of starch. Results from chlorinations performed on ovalbumin, cellulose and nylon model polymers supported this postulate. The effects upon native starch and ovalbumin of radio- frequency oxygen plasma, corona discharge and ozonolysis have been examined by ESCA. The oxygen plasma and corona discharge treatments achieved more extensive modifications than chlorine. Ozonolysis produced a similar level of oxidation to that of chlorine treatment, but at a much slower rate. The effects of these novel surface treatments on the performance of starches in cake baking have not been examined.