DISPOSAL OF EXCESS BREWER'S YEAST BY RECYCLING TO THE BREWHOUSE

Waste streams high in B.O.D. are produced by the brewing process itself. These wastes are wholesome but unwanted materials that were once part of or were in intimate contact with the brewing milieu. They are not inherently foreign to the process or the product, and disposal could be accomplished by recycling to the process. We have studied the effect on brewing processes and beer flavour of recycling waste yeast slurry to the mash mixer. Beer flavour is essentially unaffected by recycling, and of the brewhouse processes only lautering is slowed at higher recycle rates. Extract (up to 1% of the total) and soluble nitrogen can be recovered from the recycled yeast, but is strongly influenced by temperature during yeast storage and mashing. Worts made with recycled yeast tend to ferment more rapidly than normal worts and tend to have a lower end gravity.     

Increasing fermentable sugar yields by high‐pressure treatment during beer mashing

High‐pressure treatment, which is an effective means of enhancing enzymatic reactions, was implemented during beer mashing to increase the production yield of fermentable sugar (FS). The malt solution was heated (62, 67, and 72°C) under pressure [0.1 (1 atm), 2, 50 and 100 MPa], and the FS was measured. The amount of FS reached an equilibrium level, which was the highest at 67°C and at 2 MPa. The pressures were 2, 50, 100, and 0.1 MPa in decreasing order of FS amount at 67°C. The temperatures were 67, 72 and 62°C in decreasing order of FS amount at 2 MPa. With a mechanistic approach, only the effect of pressure on gelatinization was analysed. The gelatinization degrees were also higher at pressures higher than 0.1 MPa. This observation highlights the positive effect (increasing the FS yield) of high‐pressure treatment on beer mashing. Copyright © 2015 The Institute of Brewing & Distilling     

啤酒生产过程中氧化还原酶系的研究

啤酒生产过程中的氧化还原酶与啤酒风味陈化紧密相关。低水分下，其耐温活性远高于其它几种酶，在麦芽中酶活升高比例最大（与大麦中的酶活相比），其在糖化过程中氧化多酚的能力远大于多酚氧化酶。糖化过程中迅速失活，而脂肪酸氧化酶在糖化起始的低温阶段仍有部分酶活，影响不饱和脂肪酸的氧化。焙燥过程中适当延长50～70℃温度段时间，可有效降低麦芽中氧化还原酶的酶活。结合这些酶的性质，从部分抑制它们的活性角度出发，在糖化过程中，于50～60℃进行隔氧处理，可经济、有效的减少影响风味氧化的前驱物质的含量。同一质量等级不同品种的麦芽的氧化还原酶系差别相当大，相应制得的麦汁中与风味氧化有关的物质含量也有较大差别，这可能是造成不同批次原料酿造的成品啤酒风味保鲜期不稳定的原因之一。     

玉米淀粉在糖化中的应用

本文介绍了玉米淀粉的特性，比较了使用玉米淀粉作辅料的优势及糖化生产中应满足的设备、工艺要求，分析了玉米淀粉代替大米作辅料对啤酒质量的影响。     

INHIBITION BY HORDEIN OF STARCH DEGRADATION

Large and small starch granules prepared from Proctor barley contain high levels of firmly bound protein. Experiments with α-amylase under simulated mashing conditions suggest that this protein limits the rate of starch breakdown during mashing. Gel electrophoresis shows hordein to be a principal component. Treatment with cysteine or malt endopeptidase changes the nature of the associated protein.     

DEXTRINS IN SORGHUM BEER

Dextrins containing from 4 to 10 glucose units were determined in sorghum malt, wort and beer by means of HPLC. Throughout a malting period of 10 days approximately 5% fermentable sugars and only trace amounts of dextrins could be detected and the pattern remained constant. During mashing, using maize adjunct and at pH 4, there was a rapid build-up of a wide range of dextrins but their content was greatly reduced during the final stages of mashing. Both sorghum and barley beer contained similar amounts of dextrins containing 4 to 9 glucose units. The majority of these dextrins was branched as their concentration was reduced to a great extent by the action of pullulanase. Dextrins containing more than 10 glucose units were detected and their concentration was also diminished by pullulanase.     

HYDROPHOBIC POLYPEPTIDE EXTRACTION DURING HIGH GRAVITY MASHING— EXPERIMENTAL APPROACHES FOR ITS IMPROVEMENT

The aim was to establish if a substantial increase in hydrophobic polypeptides could be achieved during high gravity mashing. When worts with gravities ranging from 5–20°P were analysed for hydrophobic polypeptide content it was found that there was no appreciable increase in hydrophobic polypeptide levels. Remashing of the spent grains from low and high gravity mashes demonstrated that this resulted from inefficient extraction of hydrophobic polypeptide levels during the mashing process. For example, wort produced from remashed high gravity spent grains contained 150 mg/L hydrophobic polypeptides compared to only 10 mg/L in the low gravity remashed spent grains. Experiments were conducted, employing standard mashing techniques, in an attempt to increase the extraction of hydrophobic polypeptides during high gravity mashing. Thus the use of gypsum, proteolytic stands, varying liquor to grist ratios and wheat malt addition were all investigated for their effect on hydrophobic polypeptide extraction during high and low gravity mashing. Wort analysis demonstrated that none of the techniques employed had a significant effect on hydrophobic polypeptide extraction. When wort from remashed spent grains was used as mashing in liquor for a fresh mash and the resultant worts analysed for hydrophobic polypeptides it was observed that no increase in hydrophobic polypeptide extraction was achieved. For example, wort from the remashed high gravity spent grains, containing 140 mg/L hydrophobic polypeptides, when used as mashing-in liquor, produced no increase in hydrophobic polypeptide levels in the resultant high gravity wort (230 mg/L) when compared to a high gravity wort produced using distilled water as mashing-in liquor (255 mg/L). It is therefore concluded that a saturation point has been reached and no more hydrophobic polypeptides can be extracted during mashing regardless of the procedures employed.     

THE COMPOSITION OF FINE PARTICLES WHICH AFFECT MASH FILTRATION

The fine particulate material from various types of mash has been analysed. These particles which influence the rate of wort separation consist of aggregates of protein, hemicellulose (pentosan and β-glucan), small starch granules and lipid. All grists investigated yielded such aggregates with similar qualitative composition but with marked variations in the relative amounts of individual components. There is no evidence that retrograded amylose contributes significantly to the composition of the aggregated particles. When heat stable β-glucanase is added to a mash containing 20% raw barley, neither the volume nor the β-glucan content of the fines changes appreciably but the texture is altered. The action of the glucanase loosens the structure of the particles to release small starch granules into the mash and the residual structure has a more porous appearance which probably allows freer passage of wort through the grain bed. The origin of mash-bed particles is the endosperm of the ungerminated barley or the under-modified regions of the malt.     

Optimisation of the Mashing Procedure for 100% Malted Proso Millet (Panicum miliaceum L.) as a Raw Material for Gluten‐free Beverages and Beers

Proso millet is a gluten‐free cereal and is therefore considered a suitable raw material for the manufacturing of foods and beverages for people suffering from celiac disease. The objective of this study was to develop an optimal mashing procedure for 100% proso millet malt with a specific emphasis on high amylolytic activity. Therefore, the influence of temperature and pH on the amylolytic enzyme activity during mashing was investigated. Size exclusion chromatography was used to extract different amylolytic enzyme fractions from proso millet malt. These enzymes were added into a pH‐adjusted, cold water extract of proso millet malt and an isothermal mashing procedure was applied. The temperatures and pH optima for amylolytic enzyme activities were determined. The α‐amylase enzyme showed highest activity at a temperature of 60°C and at pH 5.0, whereas the β‐amylase activity was optimum at 40°C and pH 5.3. The limit dextrinase enzyme reached maximum activity at 50°C and pH 5.3. In the subsequent mashing regimen, the mash was separated and 40% was held for 10 min at 68°C to achieve gelatinisation. The next step in the mashing procedure was the mixture of the part mashes. The combined mash was then subjected to an infusion mashing regimen, taking the temperature optima of the various amylolytic enzymes into account. It was possible to obtain full saccharification of the wort with this mashing regimen. The analytical data obtained with the optimised proso millet mash were comparable to barley wort, which served as a control.     

Dry and Wet Milling of Malt. A Preliminary Study Comparing Fermentable Sugar,Total Protein,Total Phenolics and the Ferulic Acid Content in Non‐Hopped Worts

In this work, fermentable sugar, total protein, phenolics and ferulic acid content were estimated in sweet worts at different points of lautering. Transfer of these selected malt compounds into worts was analyzed in relation to the method of malt milling (wet milling of malt — the “test worts” or dry milling of malt — the “reference worts”). Glucose, maltose and maltotriose were more rapidly transferred into sweet worts at the early stages of lautering (40 hL and/or 80 hL of wort) after wet milling in comparison to dry milling. Total protein content in the test worts was significantly higher than in the corresponding reference worts at each stage of lautering. Transfer of phenolic compounds and ferulic acid (in the free as well as in the ester form) from the mash into sweet worts was significantly improved by dry milling, but not by wet milling. No difference in the total antioxidant activity was observed between the two types of worts. In conclusion, it can be stated that wet conditioning of malt before milling enhances the fast transfer of fermentable sugars and proteins from the mash into the sweet wort during lautering. Lautering is a time‐consuming process, and time reduction without the loss of wort quality should be a priority. Therefore, wet milling can be of interest to professionals in the field as an interesting alternative method to improve the mashing process.