The Preparation And Functional Properties Of Soluble Dietary Fiber(SDF)from Wheat Bran Fermented By Neurospora Sitophila

Wheat bran was a by-product of flour processing.It was rich in active substances,such as dietary fiber,flavonoids,phenolic acids and so on.Among them,the content of dietary fiber was the largest,accounting for about 35%to 50%of the total.Therefore,wheat bran was the ideal material for extracting high-quality dietary fiber.In thwas study,Neurospora sitophila was used to prepare soluble dietary fiber(SDF)by solid-state fermentation of wheat bran.The effect of fermentation conditions on the yield of soluble dietary fiber was explored,and the optimal fermentation conditions were determined.In order to explain the possible mechanwasm of the release of SDF from wheat bran by Neurospora sitophila,the activity of cellulase and xylanase produced during the fermentation process were determined.The optimal fermentation medium was determined by Plackett-Burman experiment,minimum addition experiment,steepest climbing experiment and Box-Behnken experiment.Then,the wheat bran was fermented by the above-determined optimal method and combined with ultrasonic treatment.The SDF extraction process of wheat bran was optimized through single factor combined with orthogonal experiment,and the optimal process parameters of ultrasonic combined fermentation and extraction were explored.Finally,some physical,chemical and functional properties of wheat bran SDF extracted by different methods were determined.The main research results are as follows:(1)Through single factor experiment,Plackett-Burman experiment,minimum addition amount experiment,steepest climbing experiment and Box-Behnken experiment,the optimal fermentation condition for the yield of wheat bran SDF was determined.The inoculation amount was 10%(v/w),the water content was 70%(v/w),the fermentation temperature was 30?,and the fermentation time was 72 h.The best fermentation medium formula was lOg of wheat bran,0.7%(w/w)of glucose,0.6%(w/w)of ammonium sulfate,0.2%(w/w)of magnesium sulfate,0.3%(w/w)of dipotassium hydrogen phosphate,0.1%(w/w)of calcium chloride,0.1%(w/w)of sodium chloride.Under these conditions,the predicted wheat bran SDF yield was 6.37±0.25%,and the actual yield was 6.29 ± 0.17%.The results are relatively close,indicating that the experimental results obtained by the above model are credible and reasonable.During the fermentation process,both cellulase activity and xylanase activity are positively correlated with the yield of wheat bran SDF,and different C sources have a certain inducing effect on them.(2)Based on the research results of solid-state fermentation of wheat bran,ultrasonic-asswasted extraction of wheat bran SDF was used.The cavitation effect of ultrasonic waves in the liquid and its generating mechanical force to break off the bonds between the macromolecules.Combining the ultrasonic-asswasted extraction with above fermentation conditions,the yield of SDF was maximized.The single factor and orthogonal experiment were used to optimize the ultrasonic fermentation to extract the wheat bran SDF process.The optimal process parameters were determined as below.The ultrasonic time was 80 min,the ultrasonic power was 576W,and the ultrasonic temperature was 50?.Then the average SDF yield was 6.94±0.17%.The relative deviation was small at thwas time,proving that the experimental results obtained by the orthogonal design were accurate and reliable.(3)By comparing the physicochemical and functional properties of wheat bran SDF prepared by unfermented,fermented,and fermentation combined with ultrasound,the solubility,solubiness,oil retention,and swelling power of wheat bran SDF prepared by fermentation combined with ultrasound were all significantly increased.And in thwas condition the ability to absorb glucose and cholesterol,and scavenge DPPH free radical are also increased.