蛋白质分解的影响因素

1麦芽蛋白质含量和蛋白质溶解度的影响在麦芽的蛋白质溶解度一定时,蛋白质含量高的麦芽则在糖化时提供可溶性氮数量多,使得麦汁中的总氮含量高。为保证麦汁中的总氮一定,且不能过高,麦芽蛋白质含量应小于10.4%,否则麦汁的总氮高,会影响啤酒口味,使啤酒的非生物稳定性变差(表1)。     

麦芽蛋白溶解度与麦汁高分子蛋白的关系

测定了40个不同麦芽样品的蛋白质含量、可溶性氮、库值及高分子蛋白,并对结果进行了相关性分析。结果表明,麦汁中高分子蛋白的含量与麦芽的蛋白质含量呈显著正相关(r=0.659,P0.01),表明蛋白质含量高的麦芽制得的麦汁中高分子蛋白的量也高。此外,建立了麦汁中高分子蛋白与库值及蛋白质含量的线性回归方程,依据此方程可根据麦芽的库值及蛋白质含量预测麦汁中的高分子蛋白,为从源头上预测和控制啤酒泡沫提供支持。     

麦汁中蛋白质分布及含量对麦汁浊度的影响

研究了麦汁中蛋白质分布及含量对麦汁浊度的影响。结果表明:蛋白质分布及含量对麦汁初始浊度无影响;高、中分子蛋白将使冷藏后及强化后的麦汁浊度升高;低分子蛋白将在长期贮存中发生聚合而引起麦汁浊度升高。在酿造中应控制高、中分子蛋白的绝对含量和相对比例。     

麦汁澄清剂-卡拉胶的研究现状

麦汁澄清剂—卡拉胶能够加快麦汁中蛋白质沉淀,特别是十分有效地除去冷浊蛋白质,从而大大改善麦汁的浊度,提高啤酒的非生物稳定性。本文论述了卡拉胶的结构、性质、生产工艺、作用原理及质量标准等方面的研究现状和展望。     

麦汁煮沸与蛋白质凝聚

[概述]麦汁煮沸是基本决定麦汁组成、浓度和色泽等的生产操作,最主要的变化是蛋白质的凝聚和分离。煮沸过程中的蛋白质凝聚有两种形式:一种是在加热以及 PH 条件影响下的蛋白质变性凝固,这种形式去除的多为溶于麦汁的可凝固性氮,另一种是蛋白质与其它成分,如单宁、卡拉胶、部分酒花树脂以及金属离子的络合与复合物。麦汁煮沸去除多余的蛋白质,对酒体的组成、口味及提高啤酒的非生物稳定性有其重要意义。     

酿造过程对麦汁蛋白及其氧化特性的影响

本文研究了啤酒酿造过程尤其是糖化工艺对麦汁蛋白质含量、游离巯基含量和抗氧化活性的影响。研究结果表明：糖化过程伴随着大分子蛋白质的降解和小分子蛋白质的形成,蛋白质和游离巯基含量均呈现先上升后下降的规律;经历糖化阶段,蛋白质含量从310.63 μg/mL降至229.18 μg/mL,游离巯基含量则从0.61 μmol/g降至0.04 μmol/g,分别下降了26.22%和93.44%,这说明糖化是蛋白质和游离巯基发生关键变化的重要阶段。麦汁的蛋白质含量、游离巯基含量与ABTS自由基清除活性间呈极显著的正相关（p<0.01）,适当延长糖化时间和提高糖化温度有利于麦汁蛋白及其它具有抗氧化活性物质的溶出与积累,从而显著提高了麦汁的ABTS自由基清除活性。因此,麦汁蛋白尤其是具有抗氧化活性的脂转移蛋白1（LTP1）对麦汁的氧化稳定性具有重要贡献。     

卡拉胶在啤酒酿造中的应用

麦汁澄清剂－卡拉胶能够加快麦汁中蛋白质沉淀,特别是除去冷浊蛋质十分有效,大大改善麦汁的浊度,从而提高啤酒的非生物稳定性。     

卡拉胶在啤酒酿造过程的应用

主要论述麦汁澄清剂一卡拉胶能够加快麦汁中蛋白质沉淀,特别是除去冷浊蛋白质十分有效,大大改善麦汁的浊度,从而提高啤酒的非生物稳定性。具体从理论到实际应用方面阐述卡拉胶的特点、使用方法、注意事项以及实验小试比较和我公司在大生产的应用情况。     

啤酒麦汁外煮沸技术在高原地区的应用

<正> 麦汁煮沸是啤酒糖化过程生产麦汁的一项重要工序,它直接影响啤酒的非生物稳定性及其风味。在煮沸过程中,若煮沸条件(如煮沸温度、沸腾的状况)达到理想状态,将加速蛋白质凝聚,从而降低麦汁中的可凝固性氮的含量。若将麦汁煮拂温度提高4℃,可以达到同样的蛋白质凝固效果而煮     

麦汁澄清剂(卡拉胶)对啤酒酿造的影响

麦汁澄清剂(卡拉胶)是海洋藻类中提取的大分子 D-半乳聚糖,在麦汁煮沸时带负电荷,而麦汁中的蛋白质颗粒带正电荷,它们相遇电荷相互中和,形成电中性密实的凝聚物,达到去除麦汁中高分子蛋白质的目的,以提高啤酒非生物稳定性。我们通过一年多对卡拉胶在啤酒生产中的应用性试验,初步得出了一些有关数据,现总结如下:     

麦芽根的综合利用研究进展

主要介绍了国内外对于麦芽根综合利用的研究进展 ,对麦芽根中的蛋白质、酶及其它成分的各种利用作了详细介绍。麦芽根不仅可以直接用于微生物培养 ,风味物和调味品的生产 ,也可以制成蛋白制品、酶制品以作进一步应用 ,其综合利用前景非常好。     

不同蛋白质溶解度的小麦芽蛋白质组成及麦芽质量分析

为了研究小麦芽蛋白质溶解度与蛋白质组分及麦芽指标间的相关性,通过控制不同的浸麦度和发芽时间,制备了蛋白质溶解度分别为31.4％、33.1％、37.0％、37.6％、39.5％、40.9％、45.5％和54.2％的8种小麦芽,分析了小麦芽蛋白质组分、降解酶及麦芽基本指标.结果表明:随着小麦芽库值的增加,水溶性蛋白质含量成线性增加,醇溶性和碱溶性蛋白质呈现直线下降.小麦芽内肽酶活力与水溶性蛋白质含量、水分及浸出物呈现显著正相关(r分别为0.732、0.792和0.727),与醇溶性蛋白质含量呈现显著负相关(r=-0.734).因此小麦芽内肽酶活力的提高将有助于小麦芽浸出物的增加.小麦芽库值与水分、色度、浸出物、FAN、酸度均存在极显著正相关性(r=0.885、r=0.971、r=0.880、r=0.915和r=0.964);与浊度存在显著正相关(r=0.714);与有效酸度存在极显著负相关(r=-0.921).所以提高蛋白质溶解度小麦芽浸出物、浊度、FAN、酸度、色度等指标都会提高.比较8种小麦芽指标,蛋白质溶解度为39.5％时小麦芽指标较好.此时,浸出物为82.0％,FAN 166 mg/100 mg,糖化力为496 WK,黏度为1.61 cP,糖化时间为6 min.     

Effects of seeding rate, nitrogen rate and cultivar on barley malt quality

BACKGROUND: Crop management tools have been shown to affect barley kernel size and grain protein content, but the direct effect on malt quality is not well understood. The present study investigated the effect of seeding rate, nitrogen fertilisation and cultivar on malt quality. RESULTS: Higher seeding rates produced barley with less grain protein and smaller, more uniformly sized kernels. The small, uniformly sized kernels modified more completely, leading to malt with higher extract and lower wort β‐glucan than malt from low‐seeding‐rate barley. Increasing rates of nitrogen fertilisation caused grain protein levels to increase, which limited endosperm modification and reduced malt extract levels. AC Metcalfe showed better modification and higher malt extract than CDC Copeland, but CDC Copeland had better protein modification at higher fertilisation rates, which resulted in less reduction of malt extract as nitrogen rate increased. CONCLUSION: Higher seeding rates reduced kernel size and grain protein levels without compromising malt extract owing to better endosperm modification of the more uniformly sized kernels. Negative effects of higher nitrogen rates on malt quality can be reduced through development of cultivars with improved ability to modify protein during malting. © 2012 Her Majesty the Queen in Right of Canada     

HIGH PERFORMANCE LIQUID CHROMATOGRAPHY OF BARLEY PROTEINS: RELATIVE QUANTITIES OF HORDEIN FRACTIONS CORRELATE WITH MALT EXTRACT

Several high performance liquid chromatography (HPLC) approaches have been used to study the relationships between amounts of particular groups of grain storage proteins (hordeins) and malt extract, using two sets of barley samples. The areas of several chromatogram peaks varied between samples in a manner that correlated with malt extract. Size-exclusion HPLC of protein aggregates extracted by sonication gave negative correlations of the relative areas of the three largest chromatogram peaks with malt extract in a set of 39 samples of the one variety, but not in a set of samples of 8 varieties grown at 4–5 sites. Under reducing conditions, disulphide-bonded hordeins were quantitatively extracted and the proportion of hordein in the largest peak, comprised of D- and B-hordeins, correlated well with malt extract in both sets of samples. The hordeins sequentially extracted into 50% (v/v) 1-propanol and 50% (v/v) 1-propanol-50 mM dithiothreitol (DTT) were also analysed by reversed-phase HPLC, and could be resolved into several peaks of B-, C- and D- hordeins. Relationships between the amount of certain C- hordeins in the propanol extract, and certain B- hordeins in the propanol-DTT extract and malt extract were seen. As well as providing a better understanding of the relationship between barley grain protein composition and malting quality, these HPLC methods are useful additional methods to enable partial prediction of malt extract using un-malted barley.     

AREAS OF ABSORPTION RELATING TO MALT EXTRACT VALUE IN MODIFIED NEAR INFRA-RED SPECTRA OF BARLEY FLOUR

Determinations of milling energy, nitrogen, acid-soluble beta glucan and malt extract after micromalting, were made on grain samples of twenty nine barley cultivars. In addition the flour from unmalted grains was scanned over the near infra-red spectrum, and the scan data were subjected to a principal components analysis (PC). Predicted malt extract values resulting from an NIR multiple regression equation with PC terms, correlated well (r = 0.934) with the manual extract values. This confirms previous evidence that malt extract value depends largely on constituents in the resting grain, rather than on malt enzymes. An attempt to locate NIR absorptions relating to malting quality was made by restructuring the NIR spectrum of the samples according to the weightings modified by the regression coefficients in the PC regression equation for hot water extract value. The spectrum reconstructed in this way showed a number of absorption peaks and troughs. From comparison with previous NIR scans it was concluded that a strong peak at the wavelength 2100 nm was due to a starch absorption and this together with minor starch overtone peaks correlated positively with malt extract. Troughs at 2180 nm, 1980 nm and 1700 nm indicated a negative association between malt extract and some proteins. There were also wide troughs at 1830 and 2330 nm indicating a negative relationship between malt extract and beta glucan. Other peaks and troughs in the reconstructed spectrum could not readily be assigned to a constituent. A reconstructed protein spectrum consisted of peaks and troughs that agreed with previous assignations for protein absorbancies. A milling energy reconstruction was approximately the inverse of the malt extract spectrum, and an acid-soluble beta glucan reconstruction was relatively featureless and appeared to be due to the effects of particle size variations.     

ENZYMIC PROTEIN HYDROLYSATES FROM MALT SPROUTS

Recent literature on the use of malt sprouts is reviewed. Studies on the hydrolysis of malt sprouts by alkaline protease were carried out to determine the optimal conditions required. Under these conditions an overall 40% solubilisation of the malt sprouts was achieved which incorporated a 65% solubilisation of the total protein content. Amino nitrogen content of the malt sprouts reached 0.8% on hydrolysis. The extract from the hydrolysed malt sprouts contained approximately 40% hydrolysed protein, 40% dextrins and salts. Evaporation of this extract produces a viscous syrup and spray drying produces a hydroscopic powder containing 1.8–2.0% amino nitrogen. The protein part of the hydrolysate extract is balanced with respect to its essential amino acid content and has a low bitter taste. Data from experiments carried out on the effect of the extract on yeast fermentation indicate a significant stimulation and possible applications in the food industry.     

Composite malt with dark-purple rice malt improves the phenolic profile and antioxidant activity of malt extract

This research presents a modification of bioactive compounds of malt extract produced from Riceberry rice malt (RRM)–barley malt composite for malt-based beverage. Malt extract was produced by varying RRM at 20% w/w, 40% w/w, 60% w/w, 80% w/w, and 100% w/w and were analysed for total polyphenol content (TPC), phenolic acids constituent, and antioxidant activity. The 100% RRM extract was rich in TPC relative to 100% w/w barley malt extract. The composite malt extract containing 40% w/w–80% w/w RRM had enough TPC in the filtered malt extract (236–524 mg L⁻¹) and boiled hopped malt extract (216–485 mg L⁻¹) and were directly proportional to the antioxidant activity in the extract. Barley malt fraction in the malt extracts had a positive response on ferulic acid and sinapic acid, whereas RRM inclusion in malt extract increased p-coumaric acid, vanillic acid, rutin, and methyl coumarate concentration. Therefore, the cereal malt composite could provide strong oxidative stability to the malt extract and derived products.     

Mechanisms of Malt Extract Development in Barleys from Different European Regions: II. Effect of Barley Hordein Fractions on Malt Extract Yield

To examine environmental differences between southern and northern European malting barleys, particularly relating to protein and hordein influences on malt extract development, samples of the malting barley cultivar Alexis, from the Nordic countries and from the Iberian Peninsula, were used. Fractionation of hordeins was carried out on barley grams, prior to micromalting and malt analyses, using high performance liquid chromatography (HPLC). Different mechanisms for extract development, in malting barleys from the North and South of Europe, have been demonstrated. Barley protein content determined a significantly greater decrease in malt extract in the Nordic samples, compared with those from the Iberian Peninsula, while apparent final attenuation showed a more pronounced positive association with extract in the South than in the North. B‐hordein was associated with a significanlty greater decrease in malt extract in the Nordic compared to the Mediterranean samples.     

EVALUATION OF BARLEY AND MALT QUALITY USING NEAR-INFRARED REFLECTANCE TECHNIQUES

A scanning near-infrared reflectance spectrophotometer was calibrated for the prediction of barley aleurone colour and malt moisture. The malt moisture was predicted on malt ground for the determination of malt extract (coarse grind) making the method suitable for moisture correction in malt extract estimation. Calibrations for the prediction of malt extract and endosperm modification from barley and malt were also attempted. A correlation (r= 0.851 n = 135) was found between malt hot water extract and the percentage of the endosperm estimated as being modified by microscopy following staining with Calcofluor. Probably because of this influence of modification on malt extract, the use of near-infrared reflectance to predict malt extract was most successful at predicting the malt extract values obtained following micro-malting in the absence of the additives, gibberellic acid and potassium bromate.