| Both the emzymatic preparation of xylo-oligosaccharides(XO) and the application of XO in steamed bread made by frozen dough fermentation were studied in this paper.The enzymatic properties of Trichoderma Reesei Rut-C30 xylanase showed that the optimal enzyme activity condition was at 60℃and pH 5.0, the activity of the enzyme was stable as the temperature was lower than 60℃the pH range of 3.0 to 7.0. Enzyme kinetics studies showed that this enzyme was affinity with xylan, and the molecular weight was about 20.1kDa from SDS-PAGE results.Before hydrolyzed by xylanase, wheat bran was pretreated by several enzymes, which was better than pretreated by water washing. 26.07% xylose and XO(1.36% xylobiose, 5.42% xylotriose, 11.66% xylotetraose and 5.66% xylopentaose) were detected from hydrolyzate by the method of high performance liquid chromatography (HPLC) as well as little arabinose and glucose. Response surface methodology(RSM) were used to optimize the experimental conditions: 1832U/g of xylanase; 8.3% of substrate concentration and 49.5℃of reaction temperature.The thermo-mechanical indexes of dough, which detected using mixolab, showed that XO could strengthen dough gluten, improve the kneading resistance and cooking property of dough. The ferment rheology properties of frozen dough was detected using rheofermentometer F3, the results showed that H'm-the maximum height of gas release curve, Hm-the maximum height of dough development curve and gas retention rate of dough were all increased after adding XO. Therefore, XO to some extent showed cryoprotective effect of improving frozen dough systems.XO could improve the characteristics of steamed bread made by frozen dough fermentation effectively. After adding XO, both the height-diameter ratio and sensory score of frozen dough steamed bread were increased significantly comparing with the blank group while there was little effect of XO on the crust color L1 and crumb color L2 of steamed bread. Orthogonal experimental results showed that the highest quality of steamed bread could be produced with 1.5% XO, 4% compressed yeast and 2% trehalose. |
