Determination of elemental sulphur in soils

Elemental sulphur was extracted from soil with chloroform and the sulphur was reduced to hydrogen sulphide by iron powder in the presence of hydrochloric acid, acetone and chloroform. The hydrogen sulphide was transferred in a stream of nitrogen to sodium hydroxide solution and determined by titration with mercuric chloride using dithizone as an indicator. The reduction technique was not specific to elemental sulphur but soils appeared to contain few compounds which were soluble in chloroform and which were also reduced. Wet soils could be extracted without preliminary drying. The analysis is rapid and suitable to routine application.     

The response of double-low winter oilseed rape to fertiliser sulphur

The effect of soil-applied ammonium sulphate (10, 20, 30, 50 and 80 kg S ha^?1) and agricultural gypsum (20 and 50 kg S ha^?1) and of foliar-applied elemental sulphur (20 kg S ha^?1) on the seed yield and chemical composition of double-low cultivars of winter oilseed rape was determined at 11 sites in England during 1989-1991. Significant (P ? 0.05) mean seed yield responses to applied sulphur (S) of 10 and 17% were obtained at two sites on sandy soils in northern England which showed symptoms of severe S deficiency. At a third site on a shallow calcareous soil in south-west England, which did not show S deficiency symptoms, seed yield was consistently but not significantly increased by an average of 8%. At one of the sites in 1989, application of ammonium sulphate caused leaf scorch and, at the maximum rate of S applied, seed and oil yield were decreased. No conclusions were reached regarding the amount of S required for maximum yield response. The S treatments decreased seed oil content by an average maximum of 9 mg g^?1. Seed glucosinolate content was increased by a greater amount at the two sites in northern England compared to other sites, where increases averaged only 3 μmol g^?1. Analysis of individual glucosinolates in the harvested seed from one of the sites in northern England showed that only the alkenyl glucosinolates were increased by S application. Yield responses were best predicted by total S concentrations and N : S ratio values in young fully-expanded leaves at flowering. Foliar-applied elemental S was consistently less effective in raising leaf S content than ammonium sulphate. Gypsum was occasionally found to be less effective than ammonium sulphate as an S fertiliser.     

Forms of sulphur in sheep excreta and their fate after application on to pasture soil

Sheep were fed ³⁵S-labelled grass/clover herbage and the excreta was collected. About 74% of excretal S was in the form of urine and the remainder was in dung. Sulphate-S accounted for 74% of the urine S and the remainder was in Hi-reducible form. In dung, 80% of the S was C-bonded organic S and 20% was present as sulphate-S. ³⁵S-labelled dung was applied to undisturbed pasture microplots and the degradation and S release followed over a 9 month period under glasshouse conditions. During the first 34 days about 24% of ³⁵S was leached from the dung, mainly as sulphate-S and possibly some labile organic S. The C-bonded S in the dung was notably resistant to mineralisation. Only 14% of the applied ³⁵S was recovered by pasture plants. ³⁵S-labelled urine with either a high (1130 mg S litre^?1) or a low S concentration (280 mg S litre^?1) was applied in the field and its fate followed over a 10 month period. During the experiment 57 and 79% of the applied ³⁵S was recovered in pasture herbage in the high and low urine treatments, respectively. ³⁵S was also incorporated into soil organic matter and this reached a peak about 120 days after urine application when 52 and 30% of applied S had been incorporated in the high and low urine S treatments, respectively. With time, these levels declined as about 50% of the organic ³⁵S was mineralised and subsequently absorbed by the pasture plants. The results demonstrate that excreted S is recycled rapidly in pasture soils when it originates from urine. However, the bulk of S in dung appears to be relatively inert at least over a 9 month period.     

Chemistry of sulphur dioxide in vegetable dehydration

The state of sulphur dioxide in partially dehydrated or dehydrated foods is complex and depends on pH, ionic strength, water activity and concentration, and on the effects of anions and cations on the solubilities of sulphite and disulphite salts. The chemical basis of the preservative action is explained in terms of the nucleophilicity of the sulphite ion and the possible consequences of the changing state of the additive during dehydration are evaluated. The significance of autoxidation of the sulphite ion to its fate in food, and role as an antioxidant, or prooxidant, is critically discussed. The most widely studied reaction of sulphur dioxide in food is its inhibition of non-enzymic browning; the current state of knowledge concerning the mechanism of this action is explained.
The loss of sulphur dioxide during vegetable dehydration obeys first-order kinetics. This observation is considered in terms of known first-order reactions in foods and processes which are limited by rate of diffusion. There are still insufficient data to suggest ways in which the composition of the food could be altered to reduce its requirement for sulphur dioxide during dehydration.     

Rapid analysis of sulphur in wheat grain by X-ray fluorescence spectrometry

The accurate analysis of sulphur and sulphur compounds in plant material has become a critical issue as a consequence of reduced availability of the element from the environment. A new application of a reproducible technique has been developed for the determination of sulphur in wheat grain using X-ray fluorescence spectrometry. This new application compares favourably with traditional wet chemical methods especially as it is non-destructive. The sulphur content in wheut yruin measured by X-ray ffuorescence spectrometry was found to have a lower variability and the speed of analysis was more rapid in comparison with the chemical method, enabling a faster throughput of samples. Because sample preparation is very important for accurate analysis, the problems associated with oven drying, milling and of pressing during pellet formation are discussed.     

基于有机元素分析的粉状食品中蛋白质含量的测定

目的 建立基于有机元素分析的粉状食品中蛋白质含量的测定方法。方法 采用VarioEL III型元素分析仪对16种粉状食品中蛋白质含量进行测定, 并与传统经典蛋白质测定方法——凯氏定氮法进行比较。结果 元素分析法可准确测定样品中蛋白质含量, 方法重复性和准确度均很好, 与凯氏定氮法相比, 测定结果相近, 并且具有相当的测量精度, 且有操作简单、无需复杂样品前处理、无溶剂和污染、样品需求量少、分析速度快、自动化程度高等优点。结论 元素分析法可作为凯氏定氮法的替代和补充方法, 用于粉状食品中蛋白质含量的测定。     

烤肉中脂类氧化及抗氧化研究

肉类食品中脂类的氧化会产生许多不利的影响,如使食品风味发生变化以及产生有害人体健康的物质等。本文综述了烤肉中脂类的氧化,分析了影响脂类氧化的因素,并总结了抗氧化的方法。     

Responses of breadmaking quality to sulphur in three wheat varieties

Field experiments were carried out at three sites in England to investigate the effects of S fertilisation on breadmaking quality of three winter wheat varieties (Hereward, Rialto and Spark) in the 1996–1997 season. The soils at the three sites differed in extractable S contents. Depending on site, either 180 and 230 kg ha⁻¹ N or 230 and 280 kg ha⁻¹ N treatments were factorially combined with three S treatments (0, 20 and 100 kg ha⁻¹ S). Addition of S increased loaf volume significantly at two sites where grain S concentration was also significantly increased and grain N:S ratio decreased. Application of the extra 50 kg ha⁻¹ N increased grain protein concentration but did not increase loaf volume at any of the sites. Loaf volume was found to correlate more closely with grain S than with grain protein concentration. Addition of S generally decreased the elastic modulus of gel protein and dough resistance but increased dough extensibility. Despite considerable differences in their dough rheology, the responses in rheology and loaf volume to S were similar in all three varieties. Selected flour samples of Rialto from the Bridgets site were also analysed for the glutenin subunit distribution, showing that S addition increased the relative proportion of low-molecular-weight subunits at the expense of high-molecular-weight subunits of glutenin. This study therefore shows that the beneficial effects of S on breadmaking quality are associated with decreased dough elasticity and increased extensibility resulting from effects on the amount and composition of the glutenin polymers. The results also indicate that S fertilisation is required in some areas of England to maintain breadmaking quality. © 1999 Society of Chemical Industry     

Influence of packaging film permeability and residual sulphur dioxide on the quality of pre-peeled potatoes

The effects of sodium bisulphite concentration and gas permeability of the packaging film on the surface colour, texture, exudate production and microbial growth of pre-peeled refrigerated potatoes were evaluated to determine shelf-life and the lowest level of preservative which could be used.
The product was packaged in polyethylene film, or in vacuo , using EVA-SARAN-EVA laminate and stored refrigerated. Polyethylene was not adequate in several aspects; packaging in oxygen barrier film allowed reduction of bisulphite levels, and vacuum packaging of 50 ppm bisulphite treated samples doubled the shelf-life of the product compared with aerobic packaging.     

硫磺熏蒸前后银耳中6种有害金属元素的变化研究

通过在实验室模拟硫磺熏蒸的手段,采用微波消解电感耦合等离子体质谱法（ICP-MS）对硫磺熏蒸前后银耳中铅、砷、汞、镉、铬、铜6种有害金属含量进行测定。结果表明,随着熏蒸时间的增加,经过硫磺熏蒸的银耳砷的含量显著提高,汞含量也有一定程度的上升,而其他4种元素没有明显变化。硫磺熏蒸作为一种食品处理方法,其对食品品质的影响及安全性有待进一步的考量。      

固体进样等离子体光谱技术在食品元素分析中的应用

固体进样等离子体光谱技术兼具固体进样无需消解、进样效率高、简单、快速、环保以及等离子体光谱动态线性范围宽、灵敏度高、多元素分析的优势,在食品元素分析中具有良好的应用前景。本文综述了固体进样等离子体光谱技术用于食品元素分析的样品制备、样品导入及分析仪器的研究现状,重点对直接固体进样和悬浮液进样方式,电热蒸发、样品直接插入、激光烧蚀、激光诱导击穿等样品导入方式,以及样品均匀性、基体干扰与标准曲线等主要问题进行了探讨和展望。      

探讨高盐废水单质分盐及资源化利用的展望

化工行业的废水中含有大量的盐分,该类废水成分复杂、有毒有害物质多,是目前各类废水处理中的重点、难点环节.如高盐废水直接排放或管理不善会污染环境,且会造成资源的浪费,因此需要合理应用现代化技术对其资源进行有效应用.本文探讨高盐废水单质分盐及资源化利用,以期为相关人士提供参考借鉴.     

A survey of the sulphur content of wheat grown in Britain

In a survey of the sulphur content of wheat grown on British farms in 1981 and 1982 the percentage of sulphur in the grain ranged from 0.13% to 0.21%, equivalent to 0.11–0.18% at 14% moisture content, with a mean of 0.17%. The nitrogen-to-sulphur ratios, indicators of baking quality, were 11.5:1 and 13.1:1 in 1981 and 1982, respectively. The larger value in 1982 is attributed to the crop taking up much nitrogen during the exceptionally wet June. The ratio, however, was not critical in any sampler. Mean sulphur contents computed for ADAS regions showed that, generally, grain grown in the English Midlands, Eastern counties and South East contained the most sulphur, and that in Scotland least. Maps of both sulphur content and the proportion of sulphur that occurs as sulphate were made by simple block kriging with blocks 14 × 14 km. These showed that above-average sulphur contents occurred mainly in a belt of country extending from London to the West Midlands and South Yorkshire, with a maximum in the vicinity of Peterborough. Crops grown in Scotland contained least. The pattern corresponds closely with the deposition from the atmosphere predicted by the Central Electricity Research Laboratories. The distribution of sulphate as a percentage of total sulphur also had a marked regional pattern with largest concentrations in Cheshire, South Yorkshire, Fife and the rural Midlands of England.     

Effect of sulphur deficiency on the growth and metabolism of sugar beet (Beta vulgaris cv Druid)

Sugar beet plants were grown in variations of a nutrient culture system to induce sulphur deficiency. The effect of sulphur deprivation on the growth and metabolism was investigated by measuring leaf area, chlorophyll content, fresh and dry weights, sulphur, nitrogen, sulphate and nitrate concentrations, glutathione and free amino acid concentrations. Both total sulphur and sulphate concentrations were markedly reduced in response to sulphur deficiency, while significant increases in arginine concentration in shoot tissue were observed. Increases were also observed in shoot nitrogen and nitrate concentrations and both shoot and root N/S ratios. These results demonstrate that total sulphur, sulphate S and sulphate as a percentage of total S are suitable indicators of sulphur deficiency in sugar beet. Arginine responds to sulphur deficiency, but its use as an indicator needs validation under field conditions. © 2000 Society of Chemical Industry     

Fenton氧化和生物法结合深度处理硫化黑印染废水

采用Fenton氧化和生物氧化结合的方法,研究硫化黑印染废水的COD去除率和处理成本。探讨了Fenton氧化的条件包括氧化时间、m(H2O2)∶m(COD)、n(H2O2)∶n(Fe2+)以及Acinetobacter sp.DS-9生物氧化法二级串联处理系统的脱硫和COD去除效果。结果表明,最佳条件为:pH=3,m(H2O2)∶m(COD)=1∶2,n(H2O2)∶n(Fe2+)=10∶1,反应90 min后,按5%的接种量接入高效硫氧化菌株Acinetobacter sp.DS-9。废水脱硫效率提高了34.5%,COD去除率提高了74%。     

水煮牛肉冷藏期间脂质和蛋白质氧化与质构特性变化

水煮处理后的牛肉条4 ℃冷藏0~5 d,探讨冷藏期间牛肉中血红素铁含量与脂质和蛋白质氧化之间的关系,以及氧化对肉品质构的影响。结果表明,随着水煮牛肉冷藏时间的延长,与0 d血红素铁含量相比,5 d时血红素铁含量显著降低(p<0.05);而5 d时非血红素铁含量相比0 d时显著升高(p<0.05);5 d时水煮牛肉的硫代巴比妥酸(TBARS)值和蛋白羰基值是0 d含量的19倍和2.67倍;游离巯基含量随着冷藏天数的增加显著降低(p<0.05);剪切力、硬度、胶粘性、咀嚼性等数值在冷藏期间均显著升高(p<0.05)。综上所述,经过水浴加热的牛肉冷藏初期血红素铁含量较高,促进TBARS值在0~1 d阶段迅速上升,冷藏后期非血红素铁含量和TBARS值升高,其促进蛋白氧化进程,水煮牛肉剪切力和硬度等数值显著上升(p<0.05)。     

中式香肠中脂肪氧化对蛋白质氧化的影响

以中式香肠为研究对象,通过对加工、储藏过程中包装、温度、光照以及抗氧化剂的不同处理,建立中式香肠的脂肪氧化模型,结合对其蛋白质氧化的跟踪检测,分析了中式香肠中脂肪氧化与蛋白质氧化之间的相关性。结果表明:对于脂肪氧化的抑制作用,有效抑制了蛋白质氧化形成羰基类物质,且与脂肪氧化初级和次级产物均表现较好的相关性;脂肪氧化对于蛋白质游离硫醇基流失的促进作用是由脂肪氧化次级产物挥发性醛类物质引起的。     

Effects of applying sodium and sulphur fertilisers on the concentrations of elements in water leached from permanent pasture

The element composition of water leached from a perennial ryegrass pasture to which isonitrogenous quantities of sodium nitrate, ammonium nitrate or ammonium sulphate fertilisers had been applied in an experiment lasting 2 years is described. The experimental design also allowed a comparison of the immediate effects of sodium nitrate in the grazing season in which the fertiliser was applied with the residual effects of applying it in the previous year. Applying sodium fertiliser in either 1992 or 1993, but not both years, increased the concentrations of sodium, potassium, magnesium, calcium and cobalt and reduced those of phosphorus and molybdenum in leachate. The application of sulphur fertiliser reduced the concentrations of zinc, copper, iron and molybdenum in leachate. It also reduced the concentrations of sodium, potassium and magnesium, but only when sodium fertiliser was applied in 1992, and not when it was applied in 1993. It is concluded that sulphur fertiliser reduces the leaching of trace elements from the soil and that, in the long term, sodium fertiliser can amplify the effect of applying sulphur fertiliser. Sodium fertiliser in moderate quantities increased the leaching of the major divalent cations but reduced the phosphorus and molybdenum concentrations in leachate. © 2002 Society of Chemical Industry