Devin J. Rose
Date of this Version
Poudel, R. 2018. Enzymatic activities and compositional properties of whole wheat flour. Ph.D. dissertation. Univ. of Nebraska-Lincoln
The numerous enzymes present in the bran and germ fractions of a wheat kernel initiate many chemical changes that affect the compositional and functional properties of whole wheat flour. This dissertation was focused on enzyme activities and compositional properties of whole wheat flour in different applications. In the first study, lipolytic activity, which leads to rancidity during storage of wheat, was affected by environment, fungicide application, disease resistance of cultivars, and the substrate being used in the assay. Subsequently, steaming of grains for 90 s before milling was found to reduce lipolytic activities and accumulation of free fatty acids during storage and reduce oxidation once the flour was made into a dough without affecting starch and gluten properties. In another study, germination of wheat increased lipolytic activities and affected several compositional and functional properties mainly due to germination time rather than drying temperature. A small proportion of germinated flour added to a whole wheat bread formulation was found to improve bread quality except when the flour from extensive germination or higher inclusion percentage was used. Next, a sensory-driven approach was taken to estimate the shelf-life of whole wheat flour. The estimated shelf life of whole wheat flour stored at 35 °C ranged from 8-11 months and was dependent on the wheat cultivar. In a comparative study between historical and modern wheat cultivars, minimal changes in compositional properties (except for tryptophan) were found due to year of introduction. Finally, evidence of the asparaginase activity in wheat kernels and their possible genotypic variation was discovered. In conclusion, the enzymatic activities and compositional properties of whole wheat flour were dependent on the genotype, environment, their interactions, and different processing methods.
Advisor: Devin J. Rose