【作者】 程细菊；

【导师】 杨瑞金；

【作者基本信息】 江南大学 ， 食品科学， 2012， 硕士

【摘要】 本文研究了一种易于工业化的富含低聚木糖的小麦麸皮饮料的酶法生产工艺。以小麦麸皮为原料,通过焙烤工艺除去令人不愉快的风味,并赋予其浓郁的焙烤麦香味。采用木聚糖酶酶解小麦麸皮中的阿拉伯木聚糖使其转化成为功能性低聚木糖,用风味蛋白酶酶解小麦麸皮中的蛋白质使其转化成为肽,用中温α-淀粉酶酶解小麦麸皮中的淀粉使其转化成为小分子糖。这些营养物质以及小麦麸皮中的可溶性矿物质和维生素等均随酶解液保留小麦麸皮饮料中,实现小麦麸皮有效成分的充分提取利用,得到风味独特、高营养价值的富含低聚木糖的小麦麸皮饮料。本研究得到的主要结果和结论如下:研究了焙烤工艺对木聚糖转化得率及对焙烤小麦麸皮感官的影响,焙烤工艺条件:180℃、20 min。用固相微萃取和气相色谱与质谱联用技术(SPME-GC-MS)分析挥发性风味物质,发现焙烤小麦麸皮相比于未焙烤小麦麸皮,减少了醛类物质,增加了大量的吡嗪类物质、糠醛及5-甲基-2-糠醛,这些物质是焙烤小麦麸皮具有浓郁焙烤麦香味的主要贡献物。研究了酶解工艺,在木聚糖酶、风味蛋白酶、中温α-淀粉酶的单因素实验基础上进行正交实验得到复合酶酶解的最佳工艺:料水比1:8,pH6.0,加入153 U/(g小麦麸皮)木聚糖酶,138 U/(g小麦麸皮)风味蛋白酶,60 U/(g小麦麸皮)中温α-淀粉酶,50℃反应4 h。木聚糖转化得率为52.02%,还原糖浓度为27.19 mg/mL,蛋白质提取率为40.14%。酶解液中低聚木糖(木二糖~木四糖)含量为6.19 mg/mL。被复合酶酶解的蛋白质,大部分转化为肽。研究了稀释、澄清及调配工艺,酶解液的稀释倍数为3倍。澄清方式为:0.1 g/L壳聚糖和0.2 g/L皂土,反应30 min,4000 r/min离心5 min。调配的最佳条件为:10 g/L蜂蜜,60 g/L白砂糖,0.75 g/L柠檬酸。通过SPME-GC-MS分析挥发性风味物质,发现焙烤小麦麸皮所制成的饮料相对于未焙烤小麦麸皮所制成的饮料,新产生大量的吡嗪、吡咯和吡啶类物质,是赋予焙烤小麦麸皮饮料浓郁焙烤麦香味的主要贡献物,并初步探讨了饮料中风味物质的形成机理。小麦麸皮饮料分别在4℃、25℃和37℃下贮藏,贮藏期间,4℃、25℃和37℃下贮藏的小麦麸皮饮料中的细菌及大肠杆菌都未检测到,说明高温瞬时杀菌(UHT)及无菌灌装效果好。37℃贮藏,可溶性固形物含量快速下降、颜色变暗、离心沉淀率显著增大,4℃和25℃下贮藏,以上指标变化不明显。4℃、25℃和37℃下贮藏的小麦麸皮饮料的pH值和木聚糖含量(主要成分为低聚木糖)均无明显变化、悬浊稳定性先略有下降后无明显变化。更多还原

【Abstract】 This paper reported an enzymatic approach of preparation of xylooligosaccharides(XOS) -enriched wheat bran beverage, which is easy to realize in industry. The unpleasant flavors of wheat bran were removed and new flavors were formed through the baking process. Xylanase was used to hydrolyze arabinoxylan in wheat bran to functional XOS. Flavorzyme was used to hydrolyze proteins to peptides. Mid-temperatureα-amylase was used to hydrolyze starch to small molecule carbohydrates. Soluble mineral, vitamins were also remained in the wheat bran beverage. The processing can achieve the goal of full use of the active ingredients in wheat bran. The as-prepared XOS-enriched wheat bran beverage has a unique flavor and high nutritional value.The results concluded from experiments were as follows.Effects of the baking process on xylan conversion yield and sensory evaluation have been studied and the optimal baking conditions were: 180℃and 20 min. On the basis of the results of SPME-GC-MS, aldehydes were reduced while pyrazines, furfural and 5-methyl-2-furfural were increased by baking, in comparison with that unbaked wheat bran. The new compounds have made remarkable contribution to the fine flavor of baked wheat bran.Xylanase, flavorzyme and mid-temperatureα-amylase were used to hydrolyze the xylan, protein and starch in baked wheat bran, respectively. Optimal conditions of the orthogonal experiments based on the single-factor experiments were solid to liquid ratio 1:8, pH6.0, 153 U/(g wheat bran) xylanase, 138 U/(g wheat bran) flavorzyme, 60 U/(g wheat bran) mid-temperatureα-amylase, reaction temperature 50℃and reaction time 4 h. Xylan conversion yield was 52.02%, reducing sugar concentration was 27.19 mg/mL, protein extraction rate was 40.14%. XOS(xylobiose to xylotetrose) content was 6.19 mg/mL in the enzymatic hydrolysates. Most of proteins were hydrolyzed into peptides.Enzymatic hydrolysates were diluted to 3 times. Clarification optimal conditions were 0.1 g/L chitosan and 0.2 g/L bentonite, reaction time 30 min, centrifuged at 4000 r/min for 5 min. Seasoning optimal conditions were 10 g/L honey, 60 g/L sugar, 0.75 g/L citric acid. On the basis of SPME-GC-MS, new flavors, including pyrazines, pyrroles and pyridines were synthesized in baked wheat bran beverage. The formation mechanism of flavors were also discussed.Wheat bran beverages were stored at 4℃, 25℃and 37℃, respectively. During the storage, bacteria and E.coli in wheat bran beverages were both not detected. During 37℃storage, the soluble solids content quickly decreased. Color became deep dark and the rate of deposition quickly increased. But during 4℃and 25℃storage, the soluble solids content, color and the rate of deposition slightly changed. During the storage, soluble xylan content (mainly XOS) and pH did not change and cloud stability firstly decreased and then slightly changed.更多还原