Distribution of Protein Composition in Bread Wheat Flour Mill Streams and Relationship to Breadmaking Quality

Cereal Chem. 84(3):271-275 Wheat protein quantity and composition are important parameters for wheat baking quality. The objective of this study was to use fractionation techniques to separate the proteins of flour mill streams into various protein fractions, to examine the distribution of these protein fractions, and to establish a relationship between protein composition and breadmaking quality. Nine break streams, nine reduction streams, and three patent flours obtained from three samples of Nekota (a hard red winter wheat) were used in this study. A solution of 0.3M Nal + 7.5% 1 -propanol was used to separate flour protein into monomeric and polymeric proteins. The protein fractions, including gliadin. albumin+globulin. HMW-GS. and LMW-GS, were precipitated with 0. IM NH4Ac-MeOH or acetone. The fractions were statistically analyzed for their distribution in the mill Wheat proteins can be divided into monomeric fractions, which include gliadin, alhumin+globulin, and polymeric glutenins, which include high molecular weight glutenin subunits (HMW-GS) and low molecular weight glutenin subunits (LMW-GS) (Singh et at 1990). Gluten proteins consist of two major fractions: monomeric gliadins and polymeric glutenins (Sapirstein and Fu 1998). When wheat flour is mixed with water, wheat gluten proteins form a continuous and viscoelastic network, and this can influence the characteristics of dough and breadmaking quality (Aussenac et at 2001). There have been numerous investigations on the relationships of the composition of each class of proteins to breadmaking quality, especially for gliadins and glutenins, which were found to be more related to wheat quality than albumins and globulins (Huang and Khan 1997). The relationship of total protein content and the amounts and proportions of gluten protein types to breadmaking quality have been well documented (Haddad et at 1995; Sapirstein and Fu 1998; Wesley et at 1999; Wang and Kovacs 2002; Cuniberti et at 2003; Uthayakumaran et a! 2003) although the exact contribution of each of these factors to end-use functionality is largely unknown (Uthayakumaran et at 2003). Several methods of separating protein fractions from bread wheat flour have been published (Melas et at 1994; Verbruggen et at 1998; Fu and Kovacs 1999: Suchy et at 2003; DuPont et at 2005). In previous research (Wang et at 2006), we have used the multistacking (MS) SDS-PAGE method to separate unreduced SDS-soluble glutenins in mill streams and to study the glutenin composition and its relationship to breadmaking quality. DuPont et at (2005) reported a method to separate and determine albumin+globulin, gliadin, and glutenin from flour samples. Melas et at (1994) used a method to precipitate HMW-GS and LMW-GS from glutenin using different concentrations of acetone. In the present study, the objective was to use these fractionation techniques to separate the protein fractions from flour mill streams, to study the distribution of protein composition in mill streams, and establish relationships between protein composition and breadmaking quality. I Department of Cereal and Food Sciences, North Dakota State University, Fargo, ND 58105. 2 Coesponding author. E-mail: [email protected] 3 USDA-ARS. Hard Red Spring and Durum Wheat Quality Laboratory, Fargo, NI) 58105. doi: 10.1094/ CCHEM-84-3-0271 © 2007 AACC International, Inc. streams. The quantities of total flour protein and protein fractions in flour were significantly different among mill streams. The ratio of polymeric to monomeric proteins in break streams was significantly greater than in the reduction streams. The relationship between protein composition and breadmaking quality showed that the quantities of total flour protein, albumin+ globulin, HMW-GS. and LMW-GS in flour were significantly and positively correlated with loaf volume. The ratio of HMW-GS to LMWGS had little association with loaf volume. The gliadin content in total flour protein was negatively and significantly correlated with loaf volume. These results indicated that the quantity and composition of protein among the mill streams was different, and this resulted in differences in breadmaking quality. MATERIALS AND METHODS Flour Mill Streams The mill streams used in this study came from three samples of a hard red winter wheat (Triticum aestivuin L.) Nekota grown in 2004 at three different locations. Each wheat sample was tempered to 16.5% moisture content and milled on a BOhler laboratory experimental mill (MLU-202) to obtain three break (B!, B2, 133), and three reduction (RI, R2, R3) flour mill streams according to Approved Method 26-21 A (AACC International 2000). For comparison purposes, a patent flour was prepared by recombining the six mill streams according to weight percentage of each fraction. A total of 18 mill streams and three patent flours were used in this