Recent investigations of gluten secondary structure in whole grain bread dough indicate that preservation of β-turns is critical for quality. The question is whether this is true for other products. An attempt was made to evaluate gluten structural changes in refined and whole grain pasta to elucidate the impact of whole grain components on the formation and structure of the gluten network in pasta. ATR-FTIR spectroscopy was used to track gluten secondary structure through most of the major processing steps in pasta processing: raw material, mixing, drying, and cooking. Protein solubility, thiol accessibility, and SDS-PAGE data were also collected to provide additional information on the nature of protein interactions and network composition. Few secondary structural differences were observed between refined and whole grain flours from hard white winter wheat. However, mixing induced a significant shift to β-sheets in refined dough that was not equally matched by whole grain dough. Drying under both high temperature-short time (HT) and low temperature-long time (LT) conditions resulted in a reversion to structural distributions similar to those for flour in both pastas. However, greater protein denaturation in HT dried samples was indicated by lower protein solubility in urea with dithiothreitol and by SDS-PAGE profiles. Cooking generated a substantial increase in β-sheets for all pastas. This structure was greatest in refined and LT samples. Further analysis of accessible thiols indicated the presence of a highly aggregated, compact gluten network in refined pasta driven by hydrophobic association, whereas the network in whole grain pasta was more loosely associated and dependent on disulphide bonding, both of which fit well with the secondary structural data. This suggests that β-sheets may be more important to pasta quality, especially texture, than β-turns.
Gluten structural evolution during pasta processing in refined and whole grain pasta: the influence of mixing, drying, and cooking
M. Marengo;
2014-01-01
Abstract
Recent investigations of gluten secondary structure in whole grain bread dough indicate that preservation of β-turns is critical for quality. The question is whether this is true for other products. An attempt was made to evaluate gluten structural changes in refined and whole grain pasta to elucidate the impact of whole grain components on the formation and structure of the gluten network in pasta. ATR-FTIR spectroscopy was used to track gluten secondary structure through most of the major processing steps in pasta processing: raw material, mixing, drying, and cooking. Protein solubility, thiol accessibility, and SDS-PAGE data were also collected to provide additional information on the nature of protein interactions and network composition. Few secondary structural differences were observed between refined and whole grain flours from hard white winter wheat. However, mixing induced a significant shift to β-sheets in refined dough that was not equally matched by whole grain dough. Drying under both high temperature-short time (HT) and low temperature-long time (LT) conditions resulted in a reversion to structural distributions similar to those for flour in both pastas. However, greater protein denaturation in HT dried samples was indicated by lower protein solubility in urea with dithiothreitol and by SDS-PAGE profiles. Cooking generated a substantial increase in β-sheets for all pastas. This structure was greatest in refined and LT samples. Further analysis of accessible thiols indicated the presence of a highly aggregated, compact gluten network in refined pasta driven by hydrophobic association, whereas the network in whole grain pasta was more loosely associated and dependent on disulphide bonding, both of which fit well with the secondary structural data. This suggests that β-sheets may be more important to pasta quality, especially texture, than β-turns.
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