醋酸酯麦芽糊精的工艺探究

以玉米淀粉为原料制备醋酸酯麦芽糊精,研究了酶解反应温度、加酶量、反应时间对酶解反应的影响。结果表明,酶解的最佳条件为反应温度90℃、加酶量60 U/g、反应时间80 min。     

麦芽糊精生产酶解DE值数学模型研究

本文应用二次回归正交旋转组合设计的方法，对影响麦芽糊精生产酶解终点ＤＥ值的各个要素进行了模型化研究，运用微机进行了参数测辨和统计分析，建立了ＤＥ值数学模型，解析了各因子和交互作用的影响，对系列麦芽糊精的开发生产和ＤＥ值的准确控制具有指导意义。     

甘薯麦芽糊精的特性研究

分析甘薯麦芽糊精的组分和测试其性能,表明:1.DE值相近的麦芽糊精,二段液化甘薯淀粉制备的产品大分子糊精含量显著低于一段液化产品;2．麦芽糊精的特性不仅与DE值大小有关．更与其组分有关:随着麦芽糊精中大小分子糊精含量增加,麦芽糊精水溶液透光率减小．稳定性减弱;干物质吸水能力降低;水溶液粘度增大;对香精的保护作用增强和对乳化剂的稳定作用增强;而麦芽糊精的美拉德反应性则随其中还原糖含量的增加而加强。     

极限糊精酶的研究进展及展望

本文介绍了极限糊精酶在淀粉降解过程中的作用，着重介绍了极限糊精酶的测定方法及两种不同来源的极限糊精酶——菠菜叶普鲁兰酶和来自细菌的普鲁兰酶的研究现状，并展望了极限糊精酶的应用和发展前景。     

麦芽糊精与麦芽低聚糖

碳水化合物是人体最主要的能量来源，本文主要叙述了淀粉质类碳水化合物概念、组成及在人体中的吸收，同时介绍了碳水化合物的两种组成麦芽糊精、麦芽低聚糖的生产、特性以及在人体中的吸收情况。     

系列麦芽糊精的研制

本文简要的介绍了麦芽糊精的定义,理化性质及用途。并报告了本试验以米粉或玉米淀粉、麦淀粉为原料,在高温α-淀粉酶作用下,经喷射液化、控制粉液不同DE 值、脱色过滤及离子交换精制、喷雾干燥的工艺流程。对酸法、酶法、酸酶法三种麦芽糊精制法作了简述。     

交联麦芽糊精与麦芽糊精吸潮性的比较

对麦芽糊精和交联麦芽糊精的吸潮性进行了研究,比较了它们在酱油粉中对产品吸潮性的影响.研究表明:麦芽糊精的吸潮性受环境的相对湿度、麦芽糊精的DE值及麦芽糊精的粒度等诸因素的影响.交联麦芽糊精的吸潮性一般低于麦芽糊精,对于DE值为15.0%的麦芽糊精,当交联度控制在沉降体积为19.30mL时,其吸潮性最低,此时的交联麦芽糊精的吸潮性比同DE值的麦芽糊精低33%.     

麦芽糊精

本文简要介绍了麦芽糊精的生产、组成、测定、功能性质以及其在食品工业中的应用。     

不同取代度醋酸酯麦芽糊精的性质研究

利用酶解法制备不同取代度的醋酸酯麦芽糊精,并对不同取代度醋酸酯麦芽糊精的理化性质进行研究。结果表明,经过醋酸酯改性后的麦芽糊精,随着取代度的增加,乳化性、乳化稳定性,冻融稳定性提高,透明度和吸湿率增加,而凝沉性降低。     

Limit Dextrinase — Does Its Malt Activity Relate to Its Activity During Brewing?

Limit dextrinase (EC 3.2.1.142) hydrolyses α‐1,6 glucosidic bonds in amylopectin and branched dextrins. Measurement of limit dextrinase activity during fermentation of unboiled wort at the pH of the wort has shown that its activity increases almost 10 fold during the first 10–15 h of fermentation and this increase in activity is unaffected by the presence of leupeptin, a cysteine protease inhibitor. The increase in activity seen when assays were carried out at pH 5.5 was much smaller and was reduced by leupeptin. The activity of limit dextrinase declined slowly during the latter part of the fermentation. It was established that the optimum pH for rapid extraction and assay of malt limit dextrinase in the absence of a reducing agent is approximately 4.5, but in the presence of dithiothreitol, at pH 5.5, activities 2–3 times higher can be obtained after 5 h extraction (600–700 mU/g dry weight). Limit dextrinase activities after 1 h extraction at mashing temperatures were below 20 mU/g dry weight if the mash pH was below 5.0. It is concluded that at pHs below 5.0, where limit dextrinase activity is below its optimum for activity, limit dextrinase activity increases due to dissociation of the inhibitor/enzyme complex. The protection from mashing temperatures of 65°C afforded by the inhibitor is lost at these lower pHs.     

大麦芽极限糊精酶的分离纯化及酶学特性分析

将大麦芽提取的极限糊精酶粗酶液,利用硫酸铵沉淀、离子交换层析和凝胶过滤色谱等分离方法对极限糊精酶进行逐步分离纯化。结果表明：纯化倍数为31.23,回收率为8.81%。经十二烷基硫酸钠-聚丙烯酰胺凝胶电泳后,图谱显示样品具有较高的纯度,分子质量约为97kD。同时研究了纯化前后极限糊精酶在不同作用环境下酶的活性变化,发现纯化后样品在温度45℃和pH 5.5左右具有最大酶活性,与粗酶液中酶活性相比具有明显差异。在体系中添加不同浓度的金属离子,结果发现,Mg2+、Ca2+、Mn2+在浓度较低时,对酶活性具有激活作用,而浓度较高时,则具有抑制作用;整体上,K+对酶活性影响不大;Zn2+、Fe2+对酶活性具有抑制作用。     

Thioredoxin in Barley: Could It Have a Role in Releasing Limit Dextrinase in Brewery Mashes?

There is not a strong correlation between the amount of thioredoxin in barley and the total protein content of the grain. The level of detectable thioredoxin decreases during germination, whereas the amount of limit dextrinase increases, for the most part in a bound form. Under no circumstances could a release of limit dextrinase in an active form be demonstrated through the agency of the thioredoxin system. By contrast the thiol agent dithiothreitol, especially in the presence of calcium, did promote the activation of limit dextrinase. Of most pronounced effect, however, was the lowering of pH. Three‐fold higher limit dextrinase activity was achieved when the pH was lowered to 4.0     

The Survival of Limit Dextrinase during Fermentation in the Production of Scotch Whisky

Limit dextrinase, is an important enzyme in the hydrolysis of starch from cereals to fermentable sugars. Work is described which demonstrates the importance of this enzyme in the production of Scotch whisky. The study considers the occurrence, survival and action of limit dextrinase (total and free) during fermentation in malt and grain distilleries. The results of both laboratory and distillery studies revealed that limit dextrinase can survive the conditions encountered during mashing and is not only present in the fermenter but its activity can increase during fermentation. This observation has important implications for the production of Scotch whisky, since the fermentation substrate (wash) is not boiled, the enzyme is therefore available to degrade dextrins into fermentable sugars, and can potentially increase the yield of alcohol.     

大麦芽根蛋白提取工艺条件优化

为充分利用大麦芽生产的副产物——大麦芽根中的蛋白资源,采用国家标准方法测定麦芽根的主要成分,通过正交试验研究碱法提取麦芽根蛋白的最佳工艺条件。结果表明:麦芽根的蛋白质、灰分、水分、脂肪及粗纤维质量分数分别为29.2%、6.9%、6.42%、1.4%和10.7%。正交试验结果表明,麦芽根中蛋白提取的最佳工艺条件为浸提液pH9.0、料液比1:25(g/mL)、浸提时间60min、浸提温度40℃,在此条件下麦芽根蛋白质的浸提率为63.5%。该工艺提取麦芽根蛋白简便且提取率高。     

A New Approach to Limit Dextrinase and its Role in Mashing*

Limit dextrinase (EC 3.1.2.41) is a debranching enzyme catalyzing the hydrolysis of α-1,6-glucosidic linkages in starch. The role of this debranching enzyme in beer brewing has been questioned due to its assumed heat lability. In the present work the effectiveness of limit dextrinase was studied under conditions mimicking brewery practice rather than in a buffer solution. It was demonstrated that typical conversion temperatures of 63–65 °C and a mash pH of 5.4–5.5 favour the action of malt limit dextrinase. The temperature optimum for the limit dextrinase of a malt extract was 60–62.5 °C, as opposed to 50 °C for purified limit dextrinase. Lowering the mash pH from 5.8 to 5.4 increased wort fermentability due to increased limit dextrinase activity. Wort fermentability was more strongly correlated to the free limit dextrinase activity of malt than to the α- and β-amylase activities.     

制麦过程中添加金属离子与赤霉素对大麦发芽过程淀粉酶系影响的研究

大麦发芽过程中,添加不同浓度的金属离子Mg2+、Ca2+、Zn2+、K+、Na+和赤霉素(GA3)对α-淀粉酶、β-淀粉酶和极限糊精酶活性有一定的激活和抑制作用;实验发现,添加量分别为:Mg2+50mg/kg,Ca2+50mg/kg,Zn2+20mg/kg,K+60mg/kg,Na+80mg/kg,GA30.5mg/kg时,对上述3种淀粉酶酶活均有一定的激活作用。与单独用金属离子或赤霉素浸麦相比,金属离子和赤霉素的配合使用对3种淀粉酶的酶活提高作用更为显著。     

Refining the Prediction of Potential Malt Fermentability by Including an Assessment of Limit Dextrinase Thermostability and Additional Measures of Malt Modification,Using Two Different Methods for Multivariate Model Development

Prediction of malt fermentability (apparent attenuation limit — AAL) by measurement of the diastatic power enzymes (DPE), α‐amylase, total limit dextrinase, total β‐amylase, β‐amylase thermostability, and the Kolbach index (KI or free amino nitrogen — FAN) is superior to the conventional use of diastatic power (DP) alone. The thermostability of β‐amylase is known to be an important factor in determining fermentability, thus the thermostability of the other relatively thermolabile enzyme, limit dextrinase, was investigated to determine if it was also useful in predicting fermentability. To facilitate this aim, methods were developed for a rapid and cost efficient assay of both β‐amylase and limit dextrinase thermostability. Internationally important Australian and international malting varieties were compared for their total limit dextrinase and β‐amylase activity and thermostability. Interestingly, the level of limit dextrinase thermostability was observed to be inversely correlated with total limit dextrinase activity. The prediction of malt fermentability was achieved by both forward step‐wise multi‐linear regression (MLR) and the partial least squares (PLS) multivariate model development methods. Both methods produced similar identifications of the parameters predicting wort fermentability at similar levels of predictive power. Both models were substantially better at predicting fermentability than the traditional use of DP on its own. The emphasis of this study was on the identification of predictive factors that can be consistently used in models to predict fermentability, because the model parameter estimates will subtly vary depending on mashing conditions, yeast strain/fermentation conditions and malt source. The application of these multivariate model development methods (PLS and MLR) enabled the identification of further potential fermentability predicting factors. The analyses divided the predictive parameters into those defined by DP enzymes and those associated with modification (KI, FAN, fine/coarse difference, wort β‐glucan and friability). Surprisingly, limit dextrinase thermostability was not a substantial predictor of fermentability, presumably due to its negative correlation with total limit dextrinase activity. The application of these insights in the malting and brewing industries is expected to result in substantial improvements in brewing consistency and enable more specific quality targets for barley breeder's progeny selection cut‐off limits to be more precisely defined.     

The Selection of a Dried Yeast Strain for Use in the Apparent Attenuation Limit Malt Analysis (AAL) Procedure

This investigation identifies that Mauribrew Lager 497 strain of dried yeast can be used as a standard strain for the determination of malt apparent attenuation limit (AAL). It provides ferment‐ability results for malt quality evaluation laboratories that are comparable to fresh brewery yeast. It was found that the optimal pitching rate in Congress wort (EBC Analytica, 1998, method 4.5.1), was 1 g per 200 mL, pitched at 25°C and fermented for 24 h at 20°C with agitation to complete attenuation. Preliminary trials also indicated that the Mauribrew Lager 497 dry yeast may be useful to brewers for determining the wort batch attenuation characteristics by the limit gravity test. In this case a pitching temperature of 35°C was found to be optimal with all other conditions as above. For the purpose of malt quality evaluation and brewery quality control the advantages of using a standard dry yeast strain include ease and convenience of use, consistency of quality, and uniformity between laboratories when they are located in separate geographic regions.