THE EFFECT OF WORT pH ON COPPER FINING PERFORMANCE

Copper fining trials with ale and lager worts under conditions whereby the pH of wort was artificially manipulated prior to fining, demonstrated that the optimal copper fining rate decreased with increasing values of wort pH. Clarification of acidified worts (pH<4.5) was poor regardless of the rate of copper finings addition. These results suggest that the mechanism of fining action cannot be explained by a simple electrostatic model of interaction between positively charged groups present on wort poly-peptides (lysine, arginine and histidine) and negatively charged sulphonyl groups of carrageenan. Manipulation of wort pH may be exploited to ensure batch consistency in fining performance without the requirement for variation in the rate of addition of copper finings.     

PREDICTION OF WORT COLD BREAK PERFORMANCE OF MALT AND ITS APPLICATIONS

A new test for wort cold break performance of malt was developed, based on laboratory mashing and boiling, followed by adding a range of concentrations of copper finings at different wort pH values. The test predicted successfully brewery wort cold break performance, with malts being ranked on the basis of production of wort cold break which required a low concentration of copper finings for precipitation and flocculation. A relationship between wort pH and the concentration of copper finings required to give an acceptable cold break was established with both brewery and laboratory worts. A strong correlation (r = 0.922, p << 0.01) was found between copper finings concentration and the two variables wort pH and the amount of cold break protein. Differences in brewery cold break performance were explained largely by a difference in wort pH, although other as yet unidentified factors appeared to be involved. Cold break performance of malts was affected by both crop year and protein modification, but not total nitrogen or total soluble nitrogen. A brewing trial is described in which wort pH is increased at the end of boiling, leading to significant improvements in both cold break and isinglass finings performance.     

CHARACTERISATION OF BEER PARTICLE CHARGES AND THE ROLE OF PARTICLE CHARGE IN BEER PROCESSING

Streaming current measurement has been shown to be an effective tool in measuring the net charge of beer particles. Using this method, it was demonstrated that non-microbiological particles of a number of beers could be either positively or negatively charged. Copper fining has been shown to significantly affect the net charge of the NMP in the resultant beer. Increasing the copper fining rate enhances the negative net charge of the NMP to a limiting value at which the addition of further copper finings has no effect. This is believed to correspond to the complete removal of all of the positively charged NMP by copper fining. The reduction in pH during fermentation results in the production of further positively charged NMP. The presence of positively charged NMP has been shown to have an adverse effect on isinglass fining performance. These results suggest that choice of raw materials and process conditions play as much of a role in defining fining performance as does careful consideration of fining rates .     

STUDIES ON THE MOLECULAR BASIS OF WORT CLARIFICATION BY COPPER FINING AGENTS (KAPPA CARRAGEENAN)

A comparison of the fining and gelation behaviour of kappa carrageenan suggested that folding of the polymer into a helical conformation is an essential element in the mechanism of copper fining action. Factors which destabilise or prevent the formation of helices result in the reduction or removal of fining action. Finning trials with kappa, iota and lambda carrageenan suggested that fining performance decreased with increasing carrageenan sulphate content. Carrageenan mediated clarification of dialysed wort preparations exhibited a specific requirement for the presence of potassium Ions. The deterioration of fining action in worts at acidic pH was attributed to failure of helix formation rather than chemical changes in the structure of the carrageenan molecule.     

STUDIES ON THE MECHANISM OF ACTION OF COPPER FINING AGENTS (κ CARRAGEENAN)

Carrageenan mediated clarification of brewers' wort comprises two reactions: interaction between carrageenan and soluble wort polypeptides and flocculation of particulate material. The dose/response characteristics of interaction between carrageenan and soluble polypeptide material suggested that carrageenan exhibits selectivity with respect to specific polypeptide fractions. Size exclusion chromatography of worts demonstrated that carrageenan treatment resulted in reductions in fractions of relative molecular mass Mr 70 000, 40 000 and 12 000. Fining trials demonstrated that the reactivity towards soluble polypeptides is independent of the presence of insoluble particulate material. Furthermore, both interaction with soluble polypeptides and flocculation of particulate material occurred in systems fined under high (80°C) and low (20–25°C) initial temperatures and this suggested that the presence of carrageenan in a helical conformation is essential to fining action rather than conformational transitions in polysaccharide structure. Additionally, carrageenan has no effect on the levels of low molecular mass wort solutes such as nucleic acid derivatives, aromatic and heterocyclic amino acids.     

THE FINING OF BEER — AN INVESTIGATION*

A relationship between the speed with which a beer fines and the sedimentation rate of yeast in unfined beer has been established. The measurement of fining speed has been determined quantitively.     

EFFECT OF HOP SEEDS ON BEER QUALITY

Crushed hop seed may be present in hop powders prepared from seeded hops. Microbrewery trials with this material indicate that it will not affect beer quality under normal production brewing conditions.     

EFFECT OF VARIOUS POLYPHENOLS ON THE RATE OF HAZE FORMATION IN BEER

The effect of the addition of a range of monomeric, dimeric and polymeric polyphenols to beer on the rate of haze formation has been examined. Monomeric polyphenols had no significant effect on haze formation. The addition to beer of dimeric or polymeric polyphenols caused a large increase in the rate of haze formation.     

EFFECT OF CONVECTIVE MASS TRANSFER ON BEER DIAFILTRATION

The industrial application of dialysis for the de-alcoholization of beer is based on a diafiltration method, because a small positive transmembrane pressure on the beer side of the membrane is necessary to prevent ingress of water by osmosis and resulting dilution of the beer. This pressure difference introduces the new driving and convective mass transfer mechanism, which takes place simultaneously with the diffusive mechanism (specific for dialysis). The question is the influence which it has on the overall mass transfer phenomenon and selectivity of the alcohol/extract separation. An experimental investigation of beer diafiltration using two different membranes (cellulose based Cuprophane and polysulfone) was performed at different transmembrane pressure differences and flow rates. On the basis of the experimentally measured inlet and outlet concentrations the convective components of the alcohol and extract mass fluxes as well as the overall separation factor were determined. This data was analysed and compared. The results indicate that convective mass transfer stimulated extract transfer and losses and thus diminished the efficiency of selective alcohol/extract separation in beer dialysis .     

芦荟啤酒生产工艺的研究及其功效成分的检测

芦荟因其在医药、保健、美容等方面具有一定的功能,已得到了广泛的应用.从芦荟的营养保健、药理作用、提取液的制备及添加方法等方面进行研究,简述了芦荟啤酒的生产工艺、质量要求以及功效成分的测定.     

ON THE SUNSTRUCK FLAVOUR OF BEER

It has been confirmed that sunstruck flavour is due to the formation of 3-methyl-2-butene-1-thiol formed by photolysis of iso-α-acids in the presence of sulphur-containing amino acids.     

EFFECT OF WORT-EVAPORATION ON FLAVOUR AND OTHER BEER QUALITIES

Pilot scale trials have been carried out to determine the importance of evaporation during wort-boiling at atmospheric pressure. Using normal brewing materials It has been established that an evaporation of only 2% of the total volume of a wort is sufficient to produce beers of sound flavour. Further evaporation had no significant effect on the flavour or other qualities of the finished beer.     

THE RELATIONSHIP BETWEEN HAZE AND THE SIZE OF PARTICLES IN BEER

Haze measurements have been obtained for suspensions of polystyrenelatex particles of known diameter using two light scattering instruments which measure at angles of 90° and 13° respectively. The results agree well with the theory of light scattering and demonstrate the significant effects of particle size and angle of detection upon the instrumental values for haze. This information has been used to correlate the particle size distributions of a number of beers, as measured by Coulter Counter, with the corresponding, measured haze values.     

非酸催化酯化合成耐寒增塑剂AGS酸二辛酯的研究

介绍了以ＡＧＳ酸和辛醇为原料，在复合钛酸酯催化剂作用下，经酯化反应合成ＡＧＳ酸二辛酯耐寒增塑剂的方法，分析了影响反应的诸因素，得到了反应的最佳条件，ＡＧＳ酸的酯化率达９８％．产品可替代ＤＯＡ和ＤＯＳ用作耐寒增塑剂．     

THE INFLUENCE OF CONDITIONING ON LAGER BEER QUALITY

The relative contributions to lager beer quality of malt, conditioning, and other parts of the brewing process have been assessed by analytical and sensory evaluation. Backed beers, brewed and fermented under various conditions, were stored at temperatures of 12°C, 4°C or 0°C for periods ranging from 2 to 38 days before filtration and bottling. No evidence could be found to justify a need for long periods of beer storage. Although prolonged storage can provide a remedial process, correcting aspects of beer quality such as diacetyl levels, final gravity, and removal of ‘young beer’ flavour, all these features can be more rapidly, effectively and economically controlled by closer attention to materials quality and primary fermentation procedure.     

EFFECTS OF ACIDIFICATION ON PE ACTIVITY, COLOR AND ANTIOXIDANT PROPERTIES OF COLD BREAK TOMATO JUICE

ABSTRACT

Turbidity maintenance, high antioxidant activity and attractive red color are important attributes of good tomato juice. Acidification was found effective in pectin esterase (PE) inactivation and turbidity maintenance. However, no information related to the changes of antioxidant properties after enzyme inactivation by acidification has been reported. In this article, acidification of cold break tomato juice to pH 2 or 3 was conducted after extraction. The changes of antioxidant properties (content and activity) and their correlation with PE activity and color in the juice were studied. Results indicated that acidification enhanced the viscosity of tomato juice by decreasing its PE activity. Significant increases of the main antioxidant contents (lycopene, polyphenols and vitamin C) and antioxidant activities (1,1‐diphenyl‐2‐picrylhydrazyl scavenging, ferrous ion chelating ability [FICA] and reducing power), as well as red color, were also found. In addition, the acidified cold break tomato juice exhibited better FICA and reducing power than butylated hydroxyanisole andα‐tocopherol. This finding reveals the possibility of producing tomato juice with high antioxidant capacities by acidification.

PRACTICAL APPLICATIONS

The consumers' demand for healthy products with high quality toward fresh and health has increased remarkably these years. Tomato is one of the most popular vegetable juices, and its important quality aspects are color, stability and antioxidant capacity. Pectin esterase is the principal agent responsible for tomato juice stability. In addition, the goal of tomato juice processors is to optimize processing conditions by prevention of heat and oxidative damages on antioxidant components. Our results indicated that acidification may stabilize tomato juice and improve its color characteristics and main nutritional factors. Therefore, the acidification treatment could be used as a tool for providing the attractive color and enhancing the nutritional value and health‐promoting properties of cold break tomato juice.     

THE INFLUENCE OF ENTEROBACTER AGGLOMERANS ON BEER FLAVOUR

The influence of Enterobacter agglomerans (Erwinia herbicola) on the fermentation process and beer flavour was studied. The presence of E. agglomerans gave rise to increased levels of acetaldehyde, methyl acetate, diacetyl, 2,3-pentanedione and dimethyl sulphide in the final product. The concentration of these compounds was affected by the number of bacterial cells inoculated into the pitched wort.     

啤酒活性干酵母应用工艺的研究

探讨了啤酒活性干酵母（ADY）的活化条件及使用工艺。啤酒ADY的最佳活化条件为：活化液为12Bx麦汁，33℃复水，30℃活化2h。啤酒ADY的使用量为0.5%，将活化后的ADY经低温培养后进行发酵的效果更佳。