David R. Shelton

Variation in polyphenol oxidase activity and quality characteristics among hard white wheat and hard red winter wheat samples

ABSTRACT Polyphenol oxidase (PPO) has been related to an undesirable brown discoloration of wheat-based end products. Consumer acceptance and product quality are generally decreased by the darkening phenomena. Two sets of wheat samples (Triticum aestivum L.) were investigated for variation in grain and flour PPO levels. Samples included 40 advanced experimental hard white winter wheat lines grown at two Kansas locations and 10 hard red winter wheat genotypes grown at three Nebraska locations. The variability in grain and flour PPO activities was influenced by growing location and population for the hard white wheat samples. There also was a significant influence of population by growing location interactions on PPO activity in both grain and flour. Genotype and growing location both contributed to variability in flour PPO activity among the hard red wheat samples. The variation in flour PPO activities among growing locations appeared larger than variation produced by genotypes tested for the hard red whea...

Factors Influencing Yeast Fermentation and the Effect of LMW Sugars and Yeast Fermentation on Hearth Bread Quality

ABSTRACT The purpose of this study was to investigate how wheat cultivar, growth location, type of mill, LMW sugar composition of wheat flours, mixing time, and type of mixer affected yeast fermentation. Also studied was the effect of yeast fermentation and LMW sugar composition on hearth bread quality. To achieve this, 36 different flours were produced from two different mills using six different wheat cultivars grown at three locations. Yeast fermentation in doughs, measured as gas production, was determined using realtime pressure measurements and GasSmart software. A short mixograph mixing or spatula mixing was not efficient enough to rehydrate instant dry yeast. Compressed yeast and a short mixing time were enough to reach maximum fermentation rate. Maximum pressure after 210 min of fermentation was higher for instant dry yeast than for compressed yeast. Wheat cultivar and growth location had a significant effect on LMW sugar composition. Wheat cultivar, growth location, and type of mill used signifi...

Relationships between small-scale wheat quality assays and commercial test bakes

ABSTRACT Typical commercial bakeries in the United States are highly mechanized, mass-production facilities. U.S. hard wheat breeding programs use small-scale physical dough testing and pup loaf bake procedures to identify and select improved quality genotypes. The accuracy of such approaches in the prediction of commercial-scale quality performance is poorly understood. Samples from six hard red winter wheat cultivars grown in 11 locations over three harvest years were used to correlate grain hardness, small-scale test bakes, mixograph variables, and various measures of flour protein composition with quality assessments from commercial test laboratories. Samples were milled on both pilot- and small-scale mills. Protein content and 100-g pup loaf volume were more often significantly correlated with commercial test bake variables than all other small-scale variables. Stepwise multiple regression models explained, on average, ≈40% of the variation in commercial test bake procedures. Mixograph properties, pu...