Characteristics and Protein Subunit Composition of Flour Mill Streams from Different Commercial Wheat Classes and Their Relationship to White Salted Noodle Quality

Proximate characteristics and protein compositions of selected commercial flour streams of three Australian and two U.S. wheats were investigated to evaluate their effects on the quality of white salted noodles. Wheat proteins of flour mill streams were fractionated into salt-soluble proteins, sodium dodecyl sulfate (SDS)-soluble proteins, and SDS-insoluble proteins with a sequential extraction procedure. SDS-soluble proteins treated by sonication were subsequently separated by nonreducing SDS polyacrylamide gel electrophoresis (SDS-PAGE). There was a substantial amount of variation in distributions of protein content and protein composition between break and reduction mill streams. SDS-insoluble proteins related strongly to differences in protein quantity and quality of flour mill streams. The soluble protein extracted by SDS buffer included smaller glutenin aggregates (SDS-soluble glutenin) and monomeric proteins, mainly gliadin (alpha-, beta-, gamma-, and omega-types) and albumin and globulin. SDS-soluble proteins of different flour mill streams had similar protein subunit composition but different proportions of the protein subunit groups. Noodle brightness (L) decreased and redness (a) increased with increased SDS-insoluble protein and decreased monomeric gliadin. Noodle cooking loss and cooking weight gain decreased with increased glutenin aggregate (SDS-soluble glutenin and SDS-insoluble glutenin) and decreased monomeric gliadin. Noodle hardness, springiness, cohesiveness, gumminess, chewiness, tensile strength, breaking length, and area under the tensile strength versus breaking length curve increased with increased glutenin aggregate. Monomeric gliadin contributed differently to texture qualities of cooked noodles from glutenin aggregate. Monomeric albumin and globulin were not related to noodle color attributes (except redness), noodle cooking quality, and texture qualities of cooked noodles. The results suggested that variation in protein composition of flour mill streams was strongly associated with noodle qualities.