Study On The Stability Of Reconstituted Whole Wheat Flour

Whole wheat flour contains substantially nutrients and bioactive components, which arelinked to the prevention of many diseases. However, whole wheat flour is apt to deterioratedue to the presence of lipids and lipid-degrading enzymes. Lipolytic degradation leads toreduction in functionality, palatability and nutritional properties, which restricts theproduction and application of whole wheat flour. In this study, wheat bran and germ werestabilized respectively, and then each component was reconstituted according to thefarinograph characteristics. As a result, whole wheat flour with long shelf-life and highquality was obtained, which might provide a reference for the industrial production of wholewheat flour.First of all, the effects of different stabilization treatments on the storage stability,chromatism, antioxidant activities and total phenol content of wheat bran and germ wereinvestigated. They were processed respectively by extrusion (EX), infrared roasting (IR),atmospheric steaming (AS), high-pressure steaming (HPS), heat treatment (HT),UV-microwave drying (UVM) and atmospheric steam coupled with UV-microwave (AU).Lipase and lipoxygenase inactivation rates of bran were93.97%and75.1%respectively;lipase and lipoxygenase inactivation rates of germ were100%and84.89%respectively. Theresults of accelerated storage experiment indicated that AU was the most effectivestabilization method. After30days, the growth rates of FFA in stabilized wheat germ and branwere only12.8%and9.5%respectively, which were obviously lower than those in untreatedsample (124%,241.24%, respectively). Most of the stabilization methods had no significanteffect on antioxidant properties and total phenol content of bran and germ. However, whenbran was processed by EX the total phenols content decreased by28.27%, and when bran wasprocessed by AU the metal iron chelating activity increased by20.62%. Moreover, the colorof bran and germ processed by dry heat treatment was close to the raw materials, followed byAU. Finally, AU was chosen to stabilize bran and germ.Secondly, rheological properties of blends were investigated. With increasing levels ofbran, the water absorption of purpose flour and high gluten flour increased by5.64%and8.34%respectively; formation time increased by6.98%and109.3%respectively; doughstability decreased24.32%and38.71%respectively. The dough weakened obviously andfarinograph characteristics decreased significantly when the content of bran was6%.Compared with the middle gluten flour, it was easier to deteriorate for the high gluten flourwhen bran was added. When the bran particle size decreased, reconstituted flour water absorption increased，and formation time and settling time reduced. In addition, the degree ofsoftening and farinograph characteristics had little difference. The research found that withthe increasing bran particle size, water holding capacity increased, and the gluten yield ofreconstituted flour improved. The results indicated that when bran particle size was0.25-0.36mm and the content of bran was6%(w/w), it was appropriate to reconstitute wholewheat flour.Finally, the changes of storage stability and functional ingredients of reconstituted wholewheat flour were studied in this paper. The results of accelerated storage experiment(37℃)indicated that the growth rate of FFA in stabilized whole wheat flour was only34.07%, whichwas significant lower (P<0.05) than the control (117.04%). The loss rate of total phenoliccontent (14.29%) was slightly lower than the control (15.79%). The loss rate of reducingsugar content (10.96%) was lower than the control (15.95%). Furthermore, the reduced rate ofsoluble protein (11.48%) was higher than the control (7.29%).