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Sulfur, Protein Size Distribution, and Free Amino Acids in Flour Mill Streams and Their Relationship to Dough Rheology and Breadmaking Traits

¹Dept. of Cereal & Food Sciences, North Dakota State University, Fargo, ND. ²USDA/ARS Red River Valley Research Center, Cereal Crops Research Unit, Hard Spring and Durum Wheat Quality Laboratory, North Dakota State University, Fargo, ND. Names are necessary to report factually on available data; however, the USDA neither guarantees nor warrants the standard of the product, and the use of the name by the USDA implies no approval of the product to the exclusion of others that may also be suitable. ³Corresponding author. Phone: 701-239-1412. Fax: 701-239-1377. E-mail: Gary.Hareland@ars.usda.gov ⁴Dept. of Agronomy & Plant Genetics, University of Minnesota, St. Paul, MN. ⁵Dept. of Soil, Water, & Climate, University of Minnesota, St. Paul, MN.

The aim of this study was to analyze sulfur content, protein size distribution, and free amino acids in flour mill streams (FMS) and their associations to dough rheology and breadmaking traits. Break FMS had higher nitrogen and sulfur quantities than reduction FMS. The third break FMS had the highest nitrogen and sulfur contents among FMS but low bread loaf volume partly due to high ash content. Sulfur quantity had greater or equivalent correlations with dough rheology and breadmaking properties compared with nitrogen quantity when the effect of percent ash content was removed statistically. FMS also showed significant quantitative variation in HMW polymeric proteins of the SDS-unextractable fraction that had greater association with sulfur content and dough rheology and breadmaking traits than other protein fractions. Asparagine, which is a major amino acid in flour, was found at higher levels in the third break and third reduction FMS. Ratio of nitrogen to sulfur was significantly correlated with asparagine concentration (r = 0.73, α = 0.01). This study indicates that information on sulfur, protein size distribution, and free amino acid is potentially useful in research for more precise blending of FMS in commercial flour mills to meet customer specifications for high quality flour.