Fermented Modification Of Wheat Bran And Its Application In Steamed Bread

Wheat bran is rich in dietary fiber, vitamins and minerals. According to the EFSA nutritional claims on high dietary fiber products, more than 15% wheat bran was added to produce fiber-enriched steamed bread. But those high-fiber steamed bread had poor quality and low acceptance, so it is necessary for wheat bran to be modified to improve its processing characteristics and the properties of steamed bread. This paper by yeast fermentation modified wheat bran and to study its properties, explore the influence of fermented wheat bran on dough properties and the quality of steamed bread, aiming at providing scientific basis to improve the quality of high-fiber steamed bread.Firstly, this paper studied the effects of fermentation temperature and time on composition of wheat bran. The results indicated that, the components(SAX, total phenolic, phytic acid) of wheat bran had different degrees of change. At optimum temperature 30℃ fermented for 24 h by yeast, contents of SAX and total phenolic were increased by 212.06% and 42.08% respectively, phytic acid contents decreased by 33.80%.Secondly, wheat bran with xylanase-treated and untreated as control groups, the properties of fermented wheat bran were studied. The results showed that, the total phenolic contents and antioxidant activity in fermented wheat bran were significantly higher than enzyme-treated group and untreated group. The microstructure of wheat bran showed that, wheat bran with untreated had the intact cell wall, but which was destroyed and even broken in fermented wheat bran. GC-MS analysis showed that, the amount of flavor compounds in fermented wheat bran was higher than enzyme-treated and untreated groups, and fermentation of wheat bran can produce some new flavor compounds such as phenylethyl alcohol, alpha-amyl-gamma butyrolactone, decanoic acid ethyl ester, hexanoic acid ethyl ester.Thirdly, properties of farinograph, pasting, thermal and rheological of dough, moisture in the dough and secondary structure of protein were investigated to explore the impact of adding 15% fermented wheat bran on the properties of dough. The results showed that, compared with unfermented wheat bran group, water absorption of fermented wheat bran dough decreased from 68.1% to 64.2%, but the development time and dough stability had no significantly difference; peak viscosity and final viscosity increasing, pasting temperature and enthalpy decreasing; maximum height Hm increasing by 7.69%, Tx increasing 21 min, R increasing by 2.71% after adding fermented wheat bran in dough. Fourier infrared spectra results showed that, the addition of wheat bran changed the water bound to gluten matrix and gluten secondary structure, β-turn ratio increase from 16.92% to 18.16%, β-folding ratio decreased from 46.09% to 44.19%.Forth,the influence of addition of 15% fermented wheat bran on color, specific volume, texture properties, sensory scores of steamed bread were investigated. The results showed that, compared with unfermented wheat bran steamed bread, the color of fermented group was darker and in the acceptable range; the specific volume increasing significantly, hardness, gumminess, chewiness of fermented wheat bran steamed bread decreasing significantly. Fermented group sensory score was higher than untreated one.Finally, the effects of addition of 15% fermented wheat bran on the flavor compounds of steamed bread were studied. The GC-MS analysis results showed that, the total amount of flavor were increased from 89.78% to 96.38% and kinds of flavor substances increased from 68 to 71 species after fermented bran was added. Fermented wheat bran also facilitated the substances alpha- amyl gamma- butyrolactone lactone,(E)-2-heptena and 2,4-nonadienal and contributed to the formation of special flavor of steamed bread.