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1.
The method of Ikeya for the determination of volatile thiols in beer by aspiration of these compounds into mercuric acetate has been examined. Cadmium acetate has been found to be unsuitable as an absorbant for removing hydrogen sulphide since it also combines with thiols. This reagent has been replaced by aqueous zinc acetate in a separate absorption trap. The proposed modification has the advantage of enabling estimations of hydrogen sulphide and of volatile thiols to be carried out on the same sample. 相似文献
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计划亏损企业的利润完成程度指标的计算是一个尚味算解决的 问题,有人增提出用功效和纱数法来测定 之,但功效系数法所作的测定与计划完成程度指标所作的测定其结果不不可比。 相似文献
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S. J. Crossley 《Food Additives & Contaminants》2000,17(7):557-562
Significant developments have been made at the international level in the methodology for conducting dietary risk assessments. The existing chronic exposure assessment methodology has been updated so that it takes account of the level of residues to which consumers are most likely to be exposed. In addition, short-term exposure assessment methodology has also been developed. This uses portion size data and takes account of the variability in residue levels between individual units where this is appropriate to the way the commodity is consumed. Other refinements to the assessment can also be made. Although the short-term methodology has been used successfully by a number of regulatory authorities, there is a need for data on portion sizes and typical unit weights before it can be fully implemented internationally. 相似文献
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卡那霉素抗性基因是转基因植物中广泛使用的一类标志基因,近年来越来越多的转基因植物被批准商业化应用,由此衍生而来的含卡那霉素抗性基因及其编码产物的转基因食品也逐渐增多,因而其安全性受到普遍关注。FDA已批准卡那霉素抗性基因编码蛋白APH(3’)-Ⅱ可使为一类食品添加剂使用。本文对卡那霉素抗性基因的特性及其编码蛋白的安全性进行了综述评价。 相似文献
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Paul Reece 《Journal of the science of food and agriculture》1980,31(2):147-155
Increases in the free fatty acid (FFA) content of oil recovered from sprat silage have been shown to be partially due to release of FFA from their water-soluble salts on acidification and to the carry over of certain organic acid acidulants. Acid hydrolysis has been shown to be a significant contributor to oil degradation at low pH, but a heat-labile catalyst active below pH 7.0 has been shown to be a contributor to FFA levels in the oil of sprat silage incubated for long periods of time. Preparation of silages using sulphuric-formic acid mixtures and the use of a preheat treatment have been shown to reduce this activity. 相似文献
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Experimental brewing in stirred tanks has been carried out at different temperatures, pH's and agitation characteristics. A model based on biochemical pathways has been developed. The parameters have been evaluated to fit the results of diacetyl concentration evolution throughout fermentation. The resulting model has proved itself to be useful in predicting results in industrial cylindro-conical fermenters when delay due to non-agitation during the first few days is considered. 相似文献
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Designing firefighter protective clothing requires many factors to be taken into consideration. Constructional parameters along with proper selection of materials are very critical and need to be extensively studied. In the present work, construction parameters of Kevlar woven and conex non-woven materials have been studied. Full factorial experiments have been conducted by varying factors like pick density of woven cloth and punch densities of non-woven fabric at three levels at three different heat fluxes. ANOVA has been done to analyse the significance of different factors and interaction between them. Time to cause second-degree burn injury has been found to be linearly related to pick and punch densities, where as it has non-linear relationship with variation in heat fluxes. Kevlar woven material with higher pick density combined with lower punch density produced maximum time before second-degree burn occurs. 相似文献
10.
Gas chromatography on an alkaline Dowfax 9N9 column has been found to be suitable for the qualitative and quantitative analysis of alkylamines in dilute aqueous solution. The method has been applied to the analysis of trimethylamine (TMA) and dimethylamine (DMA) in fish and has been used to throw further light on uncertainties concerning the use of the “picrate” procedure for TMA determination. 相似文献
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F. B. Anderson 《Journal of the Institute of Brewing》1966,72(4):384-387
A material containing both carbohydrate and protein together with some ferulic acid, and which has pronounced foam-stabilizing activity, has been isolated from beer. A fraction similar in constitution and activity to the beer constituent has been recovered from an aqueous extract of barley flour. These materials are comparable with a glycoprotein present in wheat flour; the latter has been shown to be effective in the stabilization of beer foam. There was little difference in the amount and activity of extracts prepared from different varieties of barley. 相似文献
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Víctor Falguera Jordi PagánSalvador Garza Alfonso GarvínAlbert Ibarz 《Food research international (Ottawa, Ont.)》2011,44(6):1580-1588
The effectiveness of ultraviolet irradiation in inactivating microorganisms has been known for decades. Nevertheless, in the processing of foodstuff other important issues must be considered, such as organoleptic or nutritional properties preservation. Ultraviolet irradiation constitutes an alternative to thermal treatment that is being studied and developed to obtain a better final product sensory quality, but without neglecting microbial safety. Moreover, it has been proved that this technology can be useful to decompose some toxins that are not affected by thermal processing. In this piece of work, the effect of UV irradiation on all of these contaminants and components of liquid food has been reviewed. 相似文献
14.
Seam strength prediction using loop strength has been found to be more accurate and has been consistently used by researchers over last few decades. But the testing gauge length for loop strength has not been standardized as in the case of thread tensile strength. In this paper, effect of gauge length on thread tensile strength and elongation in loop form and straight form has been studied. 40 tex and 60 tex mercerized cotton and spun polyester threads are used for the study. It is observed that there is no significant change in the loop strength of the threads as the gauge length increases, whereas the tensile strength of all threads decreases with the increase in gauge length. Elongation % is found to change significantly in both loop and straight form during tensile testing. Therefore, it is concluded that loop strength tests can be carried out at any gauge length unlike tensile testing of straight threads. 相似文献
15.
I. C. Cantrell 《Journal of the Institute of Brewing》1987,93(6):487-495
A series of investigations into production processes is described. The interaction of grain and its environment during commercial barley steeping and germination has been examined. Deficiencies which may be induced by anaerobic conditions in steeping appear to be eliminated during germination. Conversely, malt quality may be affected by excessive steep aeration. In a study of commercial brewery fermentations the importance of wort production procedures in allowing an adequate supply of unsaturated fatty acids, essential for satisfactory attenuation, has been demonstrated. Differences in fermentation behaviour cannot be fully explained by the observed yeast sterol contents. Yeast glycogen does not appear to limit fermentation performance. The application of cross-flow membrane filtration (ultra- and microporous filtration) to the recovery of beer from conditioning tank residues has been examined. The pilot-scale production of high quality permeates, and the successful blending of permeate into finished beer, have been demonstrated. The economic advantages of the ultrafiltration process are assessed briefly. 相似文献
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R. A. Aitken A. Bruce J. O. Harris J. C. Seaton 《Journal of the Institute of Brewing》1968,74(5):436-440
A simple thin-layer chromatographic procedure for the quantitative analysis of beer bittering substances is described. In the beers examined, 88–100% of the Brenner determination can be attributed to isohumulones A and B and the ratios of these two isomers show a real variation. Alpha-acids have been shown to be present in our beers. Thin-layer chromatography has also been adapted for analysis of hop resins and with fresh hops excellent agreement has been obtained with the conductometric method of analysis. 相似文献
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A new method for the estimation of fatty substances has been tested. In this the ground sample is extracted successively with acetone and chloroform in the cold and the resulting non-volatile extract is weighed. The method has been found to be quicker and to give smaller errors both within and between laboratories than the method hitherto recommended and has accordingly been adopted as the recommended method of the Institute for fatty substances in cereal adjuncts. 相似文献
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Consumption of green tea (Camellia sinensis) may provide protection against chronic diseases, including cancer. Green tea polyphenols are believed to be responsible for this cancer preventive effect, and the antioxidant activity of the green tea polyphenols has been implicated as a potential mechanism. This hypothesis has been difficult to study in vivo due to metabolism of these compounds and poor understanding of the redox environment in vivo. Green tea polyphenols can be direct antioxidants by scavenging reactive oxygen species or chelating transition metals as has been demonstrated in vitro. Alternatively, they may act indirectly by upregulating phase II antioxidant enzymes. Evidence of this latter effect has been observed in vivo, yet more work is required to determine under which conditions these mechanisms occur. Green tea polyphenols can also be potent pro-oxidants, both in vitro and in vivo, leading to the formation of hydrogen peroxide, the hydroxyl radical, and superoxide anion. The potential role of these pro-oxidant effects in the cancer preventive activity of green tea is not well understood. The evidence for not only the antioxidant, but also pro-oxidant, properties of green tea is discussed in the present review. 相似文献
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R. Eastmond 《Journal of the Institute of Brewing》1974,80(2):188-192
A dimer of catechin has been separated from a number of ales, stouts and lagers. This compound has been shown to have the same structure as procyanidin B3, which has previously been isolated from plant sources. It can be conveniently synthesized from dihydroquercetin and catechin. 相似文献
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在分析面向大规模定制设计的基础上,提出了面向大规模定制的可拓配置设计方法。本文将整个配置过程分解为可拓配置推理与可拓配置变换2个部分。其中,可拓推理解决配置设计的一般设计过程,找出与客户需求相匹配的产品单元;可拓配置变换解决配置设计过程中客户需求与现有产能的矛盾问题,通过查找不能满足客户需求的产品单元属性,发散出与这个属性相关的产品单元,再通过可拓学中的变换理论及方法,改变相应的产品单元,最终组合成客户满意的产品。本文以电钻为例,分析其成组机构,建立了电钻的产品主模型。在电钻产品物元模型上,应用可拓推理机制,提出了一套配置设计的设计算法,按照可拓变换的原理完成了对不符合要求的电钻部件的变换设计。 相似文献