Modification of granular starch with protein

This research was undertaken to modify starch with natural products, namely proteins. Motivation for this project was a 1943 patent by A. D. Fuller, which described a modified starch product, made with various substances in the presence of small amounts of hypochlorite (NaClO), that behaved like a crosslinked starch (characterized by an increase in peak viscosity and a decrease in breakdown). In this project, starch was modified by oxidation with NaClO in the presence of various proteins. After modification, excess protein was washed from the granules with water. The specific objectives of this research were to: (1) reproduce the reported preparation of crosslinked starches via oxidation in the presence of proteins, (2) optimize the reaction, and (3) determine the nature of the chemical crosslinks. The reported preparation of crosslinked starches via oxidation in the presence of proteins could be reproduced with tapioca starch. With common corn, waxy corn and potato starch, oxidation alone was enough to increase peak viscosity and decrease breakdown as determined by rapid viscoanalysis, and little difference was obtained with added protein. The reaction of tapioca starch oxidized in the presence of soy isolate protein was optimized using statistical response surface methodology. Optimum reaction conditions were found to be 0.75 mg active chlorine/g starch, 0.75 mg soy isolate protein/g starch, and pH 9. Determination of the nature of chemical crosslinks was attempted by testing the amount of protein remaining in tapioca starch granules oxidized in the presence of protein and comparing the value to the value of control starches. The results were not conclusive, as oxidation of protein decreased the amount of measurable protein. The conclusion of this research was that the oxidation of starch in the presence of protein is not an effective method of crosslinking