有机大麦发芽过程中淀粉酶的变化

本文研究了11种地方品种大麦（普通大麦）和相对应的麦芽。根据相同的合约,11种大麦在相同气候和土壤条件下种植。为了确定相同种植条件下的大麦样品在糖化过程中的酶活变化,所有试样测定了α-淀粉酶和β-淀粉酶的活力。另外,通过SDS—PAGE测定了发芽过程中蛋白质类型的改变。每个大麦试样的蛋白质含量、淀粉酶数量和质量之间都有差别,尽管通过sDS—PAGE分析Betamy1提取液（含β-淀粉酶）得到两个务带41-42kDa和55—58kDa,但由于仅仅55—58kDa带有差别,因此考虑只用它来评估大麦是否适合于啤     

不同品种小麦发芽过程中淀粉酶活力变化规律的研究

以26个小麦品种（系）为材料,研究了小麦发芽过程中淀粉酶的变化.结果表明,小麦α-淀粉酶和β-淀粉酶的活力均随发芽天数的增加而增大直至达最大值,不同品种同一发芽阶段的小麦其β-淀粉酶活力差别较大,同一品种同一发芽阶段的小麦其β-淀粉酶活力是α-淀粉酶的100倍左右.     

小麦发芽α-淀粉酶活力及相应条件下淀粉黏度的研究

通过正交试验分析发芽条件(发芽温度,发芽时间,浸泡时间)对小麦发芽过程中α-淀粉酶活力和其淀粉黏度变化.结果表明:在选定的水平下,得到α-淀粉酶活力最高的发芽条件为15℃,发芽6 d,浸泡3 d;g淀粉黏度值最大的发芽条件为20℃,发芽6d,浸泡3 d.α-淀粉酶活力与淀粉黏度随时间变化成反比关系     

发酵时间对酵子中少根根霉淀粉酶活力的影响

本文以传统酵子为分离对象，采用PDA分离纯化，通过低倍放大镜观察菌落，显微镜观察菌丝和子实体结构的形态，以及菌种的生理特征，对分离出的纯菌种进行鉴定，得到纯种少根根酶。利用制作酵子的原料和方法制得纯少根根酶曲，对其淀粉酶活力进行测定：用origin软件对数据进行处理，得出在分别发酵49h和58h时，α-淀粉酶活力和β-淀粉酶活力达到最强。     

发酵时间对酵子中少根根霉淀粉酶活力的影响

本文以传统酵子为分离对象,采用PDA分离纯化,通过低倍放大镜观察菌落,显微镜观察菌丝和子实体结构的形态,以及菌种的生理特征,对分离出的纯菌种进行鉴定,得到纯种少根根酶.利用制作酵子的原料和方法制得纯少根根酶曲,对其淀粉酶活力进行测定;用origin软件对数据进行处理,得出在分别发酵49h和58h时,α-淀粉酶活力和β-淀粉酶活力达到最强.     

山药多糖对α-淀粉酶活力的抑制作用

研究了山药多糖对α-淀粉酶活力的抑制效果,并比较了不同处理方法得到的山药多糖对α-淀粉酶活力的抑制效果,研究了多糖浓度对α-淀粉酶活力抑制效果的影响。实验结果表明,山药多糖YP、MYP及YPc对α-淀粉酶活力均具有一定的抑制作用。     

山药多糖对α-淀粉酶活力的抑制作用

研究了山药多糖对α-淀粉酶活力的抑制效果,并比较了不同处理方法得到的山药多糖对α-淀粉酶活力的抑制效果,研究了多糖浓度对α-淀粉酶活力抑制效果的影响。实验结果表明,山药多糖YP、MYP及YPc对α-淀粉酶活力均具有一定的抑制作用。      

耐高温α-淀粉酶活力测定法的研究

研究耐高温α-淀粉酶的反应动力学机理,绘制酶反应进程曲线,求得酶浓度与5min吸光度的回归方程,制订出酶浓度与吸光度关系表,从而建立了用分光光度法测定耐高温α-淀粉酶活力方法     

发芽黄豆β-淀粉酶活力的测定与比较

实验对豆类β-淀粉酶的最佳活力的条件进行了选择和比较。结果表明,在研究的豆类中黄豆的β-淀粉酶含量较高;通过对黄豆发芽前后β-淀粉酶活力的比较发现,发芽第3d中黄豆的-淀粉酶活力最高;发芽黄豆β-淀粉酶活力为最大的条件是pH5.7~6.6、温度40~50℃、最佳提取时间1.5~2.0h。     

麦曲中淀粉酶活力测定方法探讨

麦曲中淀粉酶活力一般指糖化力和液化力,它是白酒出酒率高低的重要指标。目前,各大曲酒厂多用测定麦曲中糖化力和液化力数值,为考核衡量麦曲质量和制曲车间奖金制度的依据。在测定麦曲不同淀粉酶活力时根据现有测定方法是,用脱脂棉或纱布进行过滤,但成熟的麦曲中含淀粉约50％左右,在制作曲浸泡液中同时淀粉也随着浸出,通过滤层,混合在过滤液中,使测定糖化力和液化力时,底物淀粉浓度失去标准,造成测定值与定义不符。     

α-淀粉酶法制备小麦胚芽蛋白的研究

小麦胚芽用超临界CO2脱脂,用α-淀粉酶水解麦胚蛋白提取液中的淀粉,酸沉淀麦胚蛋白,使麦胚蛋白含量和得率均较碱溶酸沉淀法明显提高,分别达到94.5%和81.36%,用高效毛细管电泳鉴定小麦胚芽蛋白的纯度,SDS-PAGE电泳测定小麦胚芽蛋白的分子量。     

麦芽糖化过程中淀粉酶酶系和酶活水平对糖化产物影响的研究

对啤酒生产中3种淀粉酶水平对糖化产物影响进行了深入的研究.在啤酒生产中淀粉酶水平的基础上,调整各淀粉酶水平,运用SAS软件设计响应面实验、处理数据,得出α-淀粉酶、β-淀粉酶、极限糊精酶3种淀粉酶水平对糖化产物的影响.     

蛀食害虫对小麦淀粉酶及过氧化物酶活性的影响

探讨玉米象(Sitophilus zeamais)、米象(Sitophilus oryzae)和谷蠹(Rhyzopertha dominica)三种蛀食性害虫不同感染程度对小麦淀粉酶及过氧化物酶活性的影响及变化规律,为小麦科学储藏量化指标提供依据。选用河南产储藏2年的商用小麦,按不同虫种分组,设定不同的虫口密度和感染时间,检测小麦样品降落数值和过氧化物酶(POD)活性,并与虫口密度和感染时间作相关性分析。结果表明,随着虫口密度增加和感染时间延长,样品的降落数值呈波动上升趋势,POD活性呈下降趋势;三种害虫侵害后的样品降落数值与感染时间均存在极显著正相关,POD活性与感染时间均存在极显著负相关,降落数值与POD之间呈极显著负相关,而二者与虫口密度的相关性均不显著。     

G4淀粉酶抑制小麦淀粉老化研究

测定G4淀粉酶处理小麦淀粉相关理化性质,如凝沉性、冻融稳定性、糊化特性、质构性、溶胀度和可溶指数等,研究G4酶对小麦淀粉抗老化性。实验结果表明:经G4淀粉酶处理后,小麦淀粉凝沉体积提高57.5%,析水率和粘度均有所降低;随温度升高,两种小麦淀粉溶胀度和可溶指数均呈现上升趋势;但G4酶处理小麦淀粉溶胀度和可溶指数明显高于原小麦淀粉,小麦淀粉凝胶硬度显著降低,G4淀粉酶具有抑制小麦淀粉老化作用。     

利用新型淀粉酶改善发酵面制品的品质

这种新型淀粉酶制剂可以改善面包和馒头制品的柔软度及弹性,延长货架期.该淀粉酶是特别为延缓焙烤制品的老化而开发的.通过作用于支链淀粉的的侧链,支链淀粉的回生将减少,面包和馒头的柔软度和弹性得到增强.该产品的另外一个好处是可以通过调节直链淀粉的分解,在总体上可以降低面包瓤的硬度,提高面包瓤的弹性.     

Effect of storage temperature on the ageing of concentrated wheat starch gels

Flour Milling and Baking Research Association, Chorleywood, Rickmansworth, Herts. Using differential thermal analysis (d.t.a.) the progress of ageing of concentrated wheat starch gels stored at temperatures from?1° to 43° has been investigated. A very close relationship has been found between the ageing of starch gels as measured by d.t.a. and the staling of bread as measured by crumb firmness at storage temperatures of?1°, 10° and 21° but some differences have been found at 32° and 43°. The results at ?1°, 10° and 21 ° provide very strong confirmatory evidence that starch crystallisation is the chief factor in the firming of bread. At elevated storage temperatures (32° and 43°) the róle of starch crystallisation in the firming of bread apparently gradually diminishes. Analysis of the results indicates that the mechanism of crystallisation of the starch, instantaneous nucleation followed by rod-like growth of crystals, is the same over the whole range of storage temperatures ?1° to 43°. Evidence is also presented to show that there is a possibility that at higher storage temperatures a more symmetrically perfect crystal structure is being formed.     

Residual amylopectin structures of amylase-treated wheat starch slurries reflect amylase mode of action

Some amylases can delay bread staling and/or starch (amylopectin) retrogradation, but the molecular basis of this effect remains little understood. In order to increase our insight in these aspects of amylase functionality, several amylases were added in a pure wheat-starch-containing model system and subjected to a heating step corresponding to that in the baking phase in bread making. Next, the effects of the limited amylolytic degradation on the rapid visco analyser (RVA) rheological properties of starch were studied and the accompanying changes in the amylopectin molecular properties (such as chain length distribution) investigated. The different amylases clearly affected the molecular structure of amylopectin to a different extent, which could be related to their mode of action and the enzyme activity levels added. Bacillus subtilis and Aspergillus oryzae α-amylases had only a limited impact on the side chain distribution of the amylopectin molecules, presumably due to their preferential hydrolysis of internal chain segments and the low enzyme activity added in the RVA. In contrast, porcine pancreatic α-amylase and Bacillus stearothermophilus maltogenic α-amylase, both with higher degree of multiple attack and used at higher enzyme activity levels, had a marked influence on the amylopectin molecular structure. More in particular, under the test conditions, the maltogenic α-amylase reduced the average chain length of the outer chains by 50%. Presumably, this will affect amylopectin retrogradation to a large extent. The results contribute to a better understanding of amylase functionality in starchy foods.     

Time course of the colour of young red wines from Vitis vinifera L. during ageing in bottle

The colour characteristics of red wines from Vitis vinifera L. cv Tempranillo, Graciano and Cabernet Sauvignon (vintage 2000) from Navarra (Spain), was studied during 26 months of ageing in bottle through the evaluation of the wine visible spectrum and of several colorimetric indices (colour intensity, %red, %yellow, %blue, %dA and tint) and CIELAB variables (L*, C*, h, a* and b*). During ageing in bottle, the spectrum of Tempranillo wine (pH 4.3) mainly changed in the absorbance range between 420 and 500 nm, whereas Graciano (pH 3.5) and Cabernet Sauvignon (pH 3.6) wines registered a decrease in absorbance in the interval between 500 and 560 nm. The time course of the different wine colour parameters was found to fit either a second‐order polynomium or a linear model, depending on the grape variety employed. CIELAB variables could be described in terms of their colorimetric index counterparts, showing b* and h relative greater errors. Although the wine total chromatic changes in CIELAB units registered after 26 months of ageing in bottle indicated changes perceivable by the human eye (ΔE* ≥ 2.7) for the three varieties studied, Graciano and Cabernet Sauvignon wines showed a more balanced colour evolution than Tempranillo wine.     

Influence of ageing on mechanical properties of wood to wood bonding with wheat flour glue

Earlier research into native wheat flour for wood to wood bonding showed excellent bonding properties comparable to synthetic adhesives, but no data about ageing behaviour is available. Short and long term effects on mechanical properties were analysed by lap joint testing and modified DCB-specimens. Results showed no significant reduction in bonding properties, but a trend to lower adhesive strength after 12 months of storage was noticeable. Changes in wheat polymers were observed by means of DSC and FTIR-ATR. Soluble degradation products of starch were analysed by GC-FID after methanolysis and derivatisation. FTIR measurements indicated changes in the structure of starch, but no appreciable alteration of proteins. Investigations by DSC showed increasing crystallinity during 3 months of storage. After 6 months more degradation products were detected. Results indicated that hydrolysis of starch is responsible for a moderate decrease of bonding performance; wheat proteins seem to be less affected.     

Inhibitory activity towards human α‐amylase in wheat flour and gluten

Wheat α‐amylase inhibitors (AI) have been targeted as potential triggers of noncoeliac gluten or wheat sensitivity (NCGS). The aim of this study was to determine AI activity towards α‐amylase from human source in wheat cultivars. Contrary to barley, buckwheat, or oats, high level of AI activity was found in wheat and, to a lesser extent, rye. AI activity (mean IC₅₀ = 137 μg mL^?1) did not vary with respect to ancient or recently developed wheat cultivars. Vital wheat gluten had very high and heat‐stable AI activity (mean IC₅₀ = 23 μg mL^?1), higher than wheat starch (?10 000 μg mL^?1) or acarbose (40 μg mL^?1), a medication for the management of hyperglycaemia and potentially causing digestive disorders due to the accumulation of undigested carbohydrates in the intestine. Data suggest that eating raw wheat gluten, flour or dough could pose a health risk.