Effects of wheat endosperm protein content and composition on white noodle quality

Noodle making quality may be predicted through an understanding of fundamental properties of flour protein and starch. A series of studies were conducted: (1) to develop a small-scale method which could discriminate among samples varying in dough strength; (2) to assess the effects of nitrogen fertilization on protein content and composition, and to investigate the effect of protein content and composition on white noodle making quality; and (3) to compare noodle making quality of flours from Canada and China.; The swelling index of glutenin (SIG) test was developed using only 40 mg flour or wholemeal. It was found that the swelling capacity of glutenin depended on swelling time and mixing intensity in non-reducing solvents. The SIG values obtained from long swelling times were positively related to gel protein and insoluble glutenin content, whereas the SIG values with short swelling times showed strong relationships with SDS sedimentation volumes and Zeleny sedimentation volumes.; The effects of nitrogen fertilization on protein composition were investigated using five spring and five winter wheat cultivars grown at six levels of nitrogen fertilization for each of two years. The sequential extraction and SE-HPLC procedures for protein fractionation resulted in similar trends of protein fractions with increased protein content, but different trends of protein fraction proportions were observed between winter and spring wheat cultivars as nitrogen fertilization increased.; The flour samples were also used to investigate effects of protein content and composition on noodle making quality including noodle processing quality, cooking quality, and cooked noodle texture. In terms of noodle processing quality, an increase in protein content produced noodles with short dough sheet length, high thickness and noodle strength as determined by the extension test. Noodles from higher protein content flour had longer optimum cooking time, lower cooking loss and water uptake, and higher cooked noodle thickness.; In addition to samples varying in nitrogen fertilization, a series of samples containing Canadian and Chinese varieties both with a wide range of protein content and dough strength were analysed. Although there were no significant differences of protein content and insoluble glutenin content between Canada Prairie Spring (CPS) and Chinese wheat flours, Chinese flours had higher soluble glutenin content, and CPS flours had higher monomeric protein content.; In the final part of this thesis, stepwise multiple regression analysis was conducted to examine the effects of the independent variables (including protein parameters and flour swelling power) on cooked noodle texture parameters. The results strongly suggested that both protein content and quality should be considered in evaluation of the suitability of flours for making white noodles. (Abstract shortened by UMI.)...