PROCESSES FOR PRODUCING BEER WITH A LOW TENDENCY TO FORM HAZE

It was confirmed that wort from malt resteeped in a solution of formaldehyde (1000 mg./litre), had a low level of anthocyanogens. It was shown that beer brewed from this malt had a lesser tendency to form haze than beer brewed from a malt resteeped in water. Malt yielding wort with usefully reduced levels of anthocyanogens could be prepared by adding formaldehyde (500–1000 mg./litre), to the final steep, in an otherwise conventional malting sequence. The rapid rate of haze formation that occurred in beers to which formalin had been added was shown to be a useful, quick guide to their stability under different storage conditions. When hydrogen peroxide (100 mg./litre) mashing liquor was added to mashes it reduced the anthocyanogen levels of the wort. The beers prepared from treated mashes were remarkably slow to form haze. The effect was greatest when hydrogen peroxide was added in small increments throughout the mashing period. The other alterations in wort characteristics resulting from this process, including marginal increases in colour and decreases in fermentability, were small. In most trials the treatment did not significantly alter the flavour of the beer. Charcoal (Norit, N.K.), added to the mash (500 mg./kg. grist), or to the copper (500 mg./kg. grist), reduced the anthocyanogen contents of the worts; the final beers had greatly enhanced shelf-lives. Charcoal was most effective when spread over the surface of the mash at the start of sparging.     

OXYGEN-SCAVENGING ENZYMES IN BARLEY AND MALT AND THEIR EFFECTS DURING MASHING

Off the enzymes that may be involved in the scavenging off oxygen radicals in barley and malt, superoxide dismutase, catalase and peroxidase all increase their specific activities during malting, whereas polyphenol oxidase decreases to zero. Of these, however, only the isoenzymes of peroxidase survive (in part) in the mash, and are responsible for the oxidation of polyphenolic materials. The concentration of hydrogen peroxide normally found in wort limits their action. Addition of hydrogen peroxide to the mash or its generation via a glucose oxidase system greatly increases haze formation, decreases the polyphenol content and causes the development of a red coloration. When the same amount of the different malt peroxidase isoenzymes was added to mashes, the intensity of the red colour varied according to the isoenzyme used. The worts produced by enhanced peroxidation afford more colloidally stable beers. The effects however are limited by the dissolved oxygen concentration in the wort.     

EFFECTS ON THE ENDOGENOUS THIOLS AND DISULPHIDES OF STEEPING BARLEY IN SOLUTIONS OF DORMANCY-BREAKING SUBSTANCES

Conditions were optimised for overcoming dormancy by steeping barley in solutions of propyl mercaptan, British anti-lewisite (BAL), thiourea, 2-mercaptoethanol and bis-(2-hydroxyethyldisulphide). The ability of the last compound to break dormancy may have been due to the living tissues of the grain, which rapidly reduced it to a thiol. Dormant barley germinated more slowly than the mature when steeped in hydrogen peroxide (0.75%), but although the level of glutathione was lower in the embryos of mature grains than in those of dormant grains after 24 h steeping, while the level of cysteine was higher after 48 h steeping, the levels of oxidised glutathione and cystine were essentially the same. Steeping in solutions of BAL retarded the germination of mature grains and accelerated the germination of dormant grains so that germination with the two types of grain, after steeping in a solution of BAL, was nearly synchronous. There were no significant differences between the levels of the thiols and disulphides in the embryos of dormant and mature grains germinating after a steep in BAL. BAL evidently reduced all endogenous disulphides in the embryos. Decorticated grains took up BAL from solution and, when sufficient thiol had been present in the initial steep, released part of it into washing water. Part of the BAL was unaccounted for, evidently it had been metabolised by the grains. Results of staining sections of steeped grains with monobromobimane and viewing under ultraviolet light to locate thiols agreed with this conclusion. Analyses of micromalts prepared by steeping dormant and mature grains with and without BAL showed that BAL retarded the modification of mature grain but accelerated the modification of dormant grain without, however, improving the performance to give a malt equal in quality to that of water-steeped, mature grain.     

氧化镁铵盐法制备高纯过氧化镁

在氯化铵溶液体系中,以氧化镁,过氧化氢为原料,制备高纯过氧化镁。研究表明采用氧化镁活性大于100,氯化铵/氧化镁不小于10%,过氧化氢∶氧化镁不小于4∶1,反应温度大于40℃情况下,反应时间不小于30 min,可制备出纯度大于90%的过氧化镁。     

双氧水氧化糯玉米淀粉工艺研究

以糯玉米淀粉为原料,双氧水为氧化剂,硫酸铜为催化剂,对氧化糯玉米淀粉的制备工艺进行了研究。考察了反应温度、反应时间、pH、双氧水用量、硫酸铜用量对氧化糯玉米淀粉羧基含量的影响。以红外光谱表征氧化糯玉米淀粉。结果表明,反应温度、反应时间、pH、双氧水用量、硫酸铜用量对糯玉米淀粉氧化均有影响。当硫酸铜用量小于0.082%时,氧化糯玉米淀粉羧基含量随着硫酸铜用量的增加而增加。糯玉米淀粉经双氧水氧化后,其糊液透明度增加,凝沉性减弱。     

THE EFFECT OF KILNING ON THE CAPABILITY OF MALT TO OXIDISE LIPIDS

The influence of kilning on the ability of malt to oxidise lipids was studied. Barley was malted with a standard programme and subsequently dried with varying kilning procedures. The capability of samples taken during kilning to oxidise lipids was determined by the lipoxygenase (LOX) reaction, i.e. by measuring O₂ consumption in an aqueous suspension of samples upon addition of excess amounts of exogenous linoleic acid. Various kilning programmes from isothermal low-temperature kilnings to kilnings with varying temperature profiles induced a two- to threefold increase in the rate of the LOX reaction in the samples taken during the first two to six hours of kilning. However, when lipid changes in the intact kernels were measured, oxidation of the endogenous malt lipids was very limited during the first half of kilning. Furthermore, the rate of the LOX reaction decreased in samples taken during the latter part of kilning, the rate of decrease depending on the kilning programme and especially the final curing temperatures. These results indicate that a possible risk of a marked ability to oxidise lipids remains at moderate kilning temperatures. In conclusion, kilning induces a significant capability to oxidise lipids but does not affect the fatty acid composition of whole kernels. However, in aqueous suspensions of ground malt the oxidative instability created might lead to oxidation of lipids .     

Methods for accelerating malting,a small scale investigation

It was confirmed that steeping fully after-ripened barley at 25° or 30°c, for various periods, induces different degrees of ‘water sensitivity’. Germination of such warm-steeped grain, set to grow at the steeping temperature, was maximal when the moisture content was about 35%. Sprays of hydrogen peroxide, applied immediately after draining the steeped grain, accelerated the subsequent germination of warm-steeped barley when grown at elevated temperatures. Exceptionally rapid steeping/germination schedules were elaborated, using micromalting techniques. For example, fully mature grain was steeped, (7 h 25°c) to a moisture content of about 36%. All subsequent processing was also at 25°c. After a drain (2 h) the grain was sprayed with a solution of gibberellic acid (0·25 mg/kg) in a dilute solution of hydrogen peroxide (2·5 vol.). Spraying with water was carried out twice more during the germination period to increase the moisture content of the barley to about 44%. The grain was set to kiln at 43°c, 48 h from steep out, that is 55 h from first wetting. Kilning conditions were chosen to allow maximal survival of enzymes. The malt had a hot water extract above 103 lb/Qr (fine grind, on dry matter) and was made at the expense of a 7·5% malting loss. It was acceptable by other analytical criteria. If the second water spray was replaced by a spray of a dilute solution of sulphur dioxide (400 mgjkg) a malt having an extract of 103·5 lb/Qr was obtained with a malting loss of 5·8%, but yielding more soluble nitrogen. The possibility of achieving even shorter processing times, by working at 30°c, was noted.     

含氧类自由基与过氧化氢脱木素

介绍了纸浆过氧化氢漂白中的含氧类自由基,如羟基自由基、过氧阴离子自由基和氢过氧自由基,以及自由基与过氧化氢脱木素及漂白的关系.讨论了这些自由基的产生、自由基与木素反应的特点、羟基自由基的脱木素选择性以及pH值对其影响,提出通过控制漂白体系中的压力、温度和过氧化氢用量来调控过氧化氢的传递、自由基的产生以及自由基浓度,合理地利用自由基反应来提高过氧化氢的脱木素能力,改善漂白效果.     

阳离子树脂催化合成环氧化大豆油的研究

以强酸性阳离子交换树脂为催化剂,考察了催化剂用量、过氧化氢与油中双键摩尔比、反应温度、乙酸用量、反应时间等因素对环氧化反应的影响.在单因素实验的基础上,通过正交实验优化确定了最佳合成条件:催化剂用量为油质量的13％,乙酸加入量为油质量的20％,过氧化氢与油中双键摩尔比为1.7∶1,反应温度68℃,反应时间7.5h;在最佳条件下制得的环氧化大豆油为淡黄色黏稠状透明液体,环氧值为6.49％.     

POLYPHENOLIC SUBSTRATES OF CATIONIC AND NEUTRAL/ANIONIC PEROXIDASES FROM BARLEY AND MALT USING A CHRONOMETRIC METHOD FOR THE DETERMINATION OF POD ACTIVITY

4-methylcatechol, phenolic acids from the benzoic and cinnamic series, flavan 3-ols and L-tyrosine were tested to determine the catalytic behavior of barley peroxidases (POD) at the expense of hydrogen peroxide. A chronometric assay using L-ascorbic acid was described for determining the peroxidatic activity of basic and neutral/anionic enzymatic fractions. The effects of hydrogen donors H₂O₂, and Ca⁺⁺ ion concentrations and pH were studied to set maximal conditions for POD measurement. The sensitivity to endogenous phenolic compounds (ferulic and p-coumaric acids, (+) catechin) along with caffeic acid for POD fractions was investigated and compared with their response versus guaiacol. Under the conditions tested, syringic and sinapinic acids as well as L-tyrosine were very weakly oxidized by POD from barley, whereas ferulic and caffeic acids were rapidly transformed. Levels of POD activity extracted from barley, green malt and kilned malt crude extracts were thereafter compared.     

光电型传感器在快速检测食品中过氧化氢的应用

实验建立的光电型传感器将显色剂-酶固定化制成试纸条,经过显色反应后,通过单色光照射试纸条,采集绿色反射光,并将其转化为电信号,制备光电型快速检测H2O2仪器测定食品中过氧化氢。结果表明,H2O2与试条反应75s后,试条显色后反射率与相应的H2O2浓度呈现良好的线性关系,线性回归方程为Y=-0.52913X 2.14664,相关系数r=0.99465(p<0.0001),检测范围为0.5mg/L至30mg/L,准确率为99.5%,RSD为2.3%,平均回收率为95.7%,检测时间低于2min,可实现过氧化氢现场快速无试剂检测。     

ROLE OF ALPHA-GLUCOSIDASE IN THE FERMENTABLE SUGAR COMPOSITION OF SORGHUM MALT MASHES*

The cause of the high glucose to maltose ratio in sorghum malt worts was studied. Mashing temperature and pH strongly affected both the amount of glucose and the proportion of glucose relative to total fermentable sugars. The relative proportion of glucose was higher when mashing was performed. at pH 4.0, close to the pH optimum for sorghum alpha-glucosidase, than at the natural pH of the mash (pH 6.0–5.5). Mashing according to the EBC procedure using an enzymic malt extract with pre-cooked malt insoluble solids producing a wort containing maltose and glucose in an approximately 4:1 ratio, whereas mashing with a malt extract without pre-cooking the malt insoluble solids resulted in a wort with approximately equal amounts of maltose and glucose. Both treatments gave the same quantity of total fermentable sugars and amount of wort extract. Sorghum alpha-glucosidase was confirmed to be highly insoluble in water. All or virtually all activity was associated with the insoluble solids. Hence, it appears that the high amount of glucose formed when sorghum malt is mashed conventionally is due to alpha-glucosidase activity. Pre-cooking the malt insoluble solids inactivates the alpha-glucosidase, preventing the hydrolysis of maltose to glucose.     

小麦氧化淀粉制备工艺及性质研究

以过氧化氢为氧化剂、硫酸亚铁溶液为催化剂、氧化淀粉糊液黏度为评价指标,通过单因素和正交试验,研究了过氧化氢浓度、催化剂浓度、反应时间等对黏度的影响。结果表明:随过氧化氢用量、反应时间和催化剂浓度的增加,淀粉的黏度逐渐变小;小麦氧化淀粉的最佳生产工艺为过氧化氢浓度为18%,催化剂浓度为0.006mol/L,反应时间为90min。     

Laboratory‐Scale Studies of the Impact of Oxygen on Mashing

An assessment of the impact of oxygen and hydrogen peroxide on mashing and wort parameters has been made on a laboratory scale. Oxygen has been stridently eliminated by using an anaerobic chamber during mash analysis. Additionally the relative importance of proanthocyanidin species has been assessed by comparing the behaviour of “conventional” malt and a malt produced from a low proanthocyanidin variety. It seems that oxygen and peroxide act independently in causing the oxidation of thiol‐containing materials and polyphenols in mashes and that oxygen is not primarily exerting its impacts through the intermediacy of peroxide. The removal of thiols (presumably at least in part through the production of disulphide bridges between proteins) and of polyphenols (presumably via polymerisation) both contribute to increased wort turbidity and decreased rates of wort separation after mashing. Three inhibitors (nordihydroguaiaretic acid, ethylenediamenetetraacetate and potassium cyanide) have been employed in an attempt to differentiate between enzymic and non‐enzymic events and also to identify whether lipoxygenase and peroxidase are catalysing key events. Whilst it seems that peroxidase has a key role in catalysing the oxidation of polyphenols by H₂O₂, it does not appear that either peroxidase or lipoxygenase is involved in the removal of measurable thiol. Nonetheless a significant proportion of the thiol elimination is likely enzyme‐catalysed. We have been unable to demonstrate the production of hydroperoxides in mashes, but added hydroperoxide is undetectable, which suggests that these materials are either lost by onward conversion or by adsorption onto spent grains.     

前处理工艺对毛/涤织物疏水改性效果的影响

针对毛/涤织物中羊毛和涤纶表面没有足够的反应活性位点,难以进行化学改性,制约了毛/涤织物在超疏水方面的表现等问题,先采用紫外光照射,再用过氧化氢对毛/涤织物进行前处理,使用二氧化硅对毛/涤织物进行疏水改性,通过静态接触角测试、扫描电镜观察、羊毛Allw?rden反应实验等方法分析前处理工艺对织物疏水性能的影响。结果表明:当织物经紫外光照射后再用双氧水处理时,紫外光照射先使羊毛表面拒水性细胞膜消除,双氧水处理进一步破坏了羊毛表面的鳞片层,使羊毛表面暴露出较多的化学反应位点,因此,硅颗粒更容易沉积在羊毛表面,赋予羊毛织物超疏水特性。     

大豆磷脂化学脱色的研究注

为了得到浅色的磷脂产品,通常采用在大豆磷脂脱色过程中加过氧化苯甲酰和氧化氢。在本实验中,采用过氧化苯甲酰和过氧化氢对浓缩磷脂进行化学脱爸,过氧化苯甲酰与过氧化氢联合使用,脱色效果最好。在本实验条件下,可得到磷脂色泽为Gardner3．5的磷脂产品。     

路边青多酚复配物对猕猴桃饮料的抗氧化稳定性影响

在猕猴桃饮料中添加路边青- 过路黄多酚复配物,考察紫外光、温度和氧化剂对饮料过氧化值的影响以及复配物配比与羟自由基清除率的关系。结果表明：90℃温度下加热6h,猕猴桃饮料中添加路边青- 过路黄多酚复配物(1:1,V/V)其过氧化值比加BHT 和不加抗氧剂分别减少8.55% 和24.57%;分别用0.5% H2O2 氧化处理和紫外光照射,添加复配物的猕猴桃饮料,其过氧化值比加BHT 分别减少9.08% 和1.83%,比不加抗氧剂分别减少17.55% 和3.57%。路边青- 过路黄多酚复配物配比以3:1(V/V)的抗氧化活性最好,饮料中添加该复配物,其过氧化值比不加抗氧剂减少56.27%;羟自由基清除率是BHT 的1.37 倍。     

非木材纤维原料的Milox制浆方法的研究

本实验研究一种以甲酸和过氧化氢为蒸煮剂的制浆过程,讨论甲酸浓度、液比、温度、H2O2用量和反应时间对蒸煮过程的影响.通过实验确定在其它条件固定的情况下,甲酸浓度88%、液比8:1为竹浆脱木质素的最佳条件;其H2O2用量2%与0.5%时相比,前者在获得相同木质素含量竹浆的同时,比后者的得率高出将近2个百分点.不同原料相比,麦草较好,实验条件下得率43.14%,卡伯值32.3,粘度980.35ml/g;嫩竹比老竹更易脱除木质素,竹浆的纤维质量最好,二重重均纤维长度都在1.7mm左右.     

ASPECTS OF ADJUNCT FERMENTATION: I. ANALYSES OF BEERS

The separate fermentation of malt wort and a carbohydrate solution (the adjunct fermentation process) is discussed in relation to factors which have to be taken into account when calculating the volumes of malt and adjunct worts which are to be fermented and to effects of this method of making beer on various aspects of beer analysis. These effects indicate that a beer of desired original gravity can be made by use of the adjunct fermentation process from about 1% less raw material than when conventional methods are used, and that the additional degree of freedom which the adjunct fermentation process introduces can be turned to account in making easier a precise control of beer analyses and in optimizing the malt: adjunct ratio to make products of desired type.     

木素在过氧化氢漂白条件下的反应

综述了木素与H2O2有关反应的研究成果,介绍了木素在常规、高温高压和氨基氰活化等啦Q漂白条件下的变化,讨论了木素在不同反应条件下进行H2O2漂白的反应机理.