施氮水平和烘烤条件对烤后烟叶品质及含氮组分的影响

以烤后烟叶主要含氮化合物之间及含氮化合物与评吸结果之间所作的统计分析表明,总氮、烟碱、蛋白质、氨基酸相互间均达1%的极显著相关,亚硝酸盐与总氮、烟碱、蛋白质分别达显著相关水平。评吸的各单项指标与含氮化合物之间大多数达到显著相关水平。香气、刺激性、吃味、劲头、甜度、总体质量与主要含氮化合物含氮化合物的多元线性回归方程在10%的显著水平上成立。低温或高温变黄使各种酶在较长时间内维持活性状态,使物质转化和积累更充分,有利于烟叶香味特征的形成,烤后烟叶品质较好。     

葡萄果实成熟过程中含氮化合物的变化

本文通过对琼瑶浆、玫瑰香、赤霞珠、小白玫瑰4个葡萄品种在果实成熟过程中硝态氮、氨态氮、总氮含量的测定,探讨了葡萄果实成熟过程中不同氮化物的变化.结果表明:4个品种在果实成熟过程中果肉和种子中硝态氮、氨态氛、总氮含量呈逐渐升高的趋势,接近成熟时其含量趋于稳定;4个品种果实种子中的硝态氮、氨态氮、总氮含量均高于果肉中的含量.     

Thermodynamic factors in partitioning and rejection of organic compounds by polyamide composite membranes

The paper analyzes the mechanism of partitioning and rejection of organic solutes by polyamide membranes for reverse osmosis and nanofiltration. The partitioning of homologous series of alcohols and polyols, in which polarity changes with size in opposite ways, was measured using attenuated total reflection IR spectroscopy. The results show that the partitioning of polyols monotonously decreases with size, whereas for alcohols it is not monotonous and slightly decreases for small C1-C3 alcohols followed by a sharp increase for larger alcohols. These results may be explained by assuming a heterogeneous structure of polyamide comprising a hydrophobic polyamide matrix and a polar internal aqueous phase. The partitioning data could consistently explain the results of rejection in standard filtration experiments. They clearly demonstrate that high/low partitioning may play a significant role in achieving a low/high rejection of organics. In particular, this points to the need to account for the partitioning effect while using molecular probes such as polyols or sugars for estimating the effective "pore" size or molecular weight cutoff of a membrane and for choosing/developing organic-rejecting membranes.     

Comprehensive bench- and pilot-scale investigation of trace organic compounds rejection by forward osmosis

Forward osmosis (FO) is a membrane separation technology that has been studied in recent years for application in water treatment and desalination. It can best be utilized as an advanced pretreatment for desalination processes such as reverse osmosis (RO) and nanofiltration (NF) to protect the membranes from scaling and fouling. In the current study the rejection of trace organic compounds (TOrCs) such as pharmaceuticals, personal care products, plasticizers, and flame-retardants by FO and a hybrid FO-RO system was investigated at both the bench- and pilot-scales. More than 30 compounds were analyzed, of which 23 nonionic and ionic TOrCs were identified and quantified in the studied wastewater effluent. Results revealed that almost all TOrCs were highly rejected by the FO membrane at the pilot scale while rejection at the bench scale was generally lower. Membrane fouling, especially under field conditions when wastewater effluent is the FO feed solution, plays a substantial role in increasing the rejection of TOrCs in FO. The hybrid FO-RO process demonstrated that the dual barrier treatment of impaired water could lead to more than 99% rejection of almost all TOrCs that were identified in reclaimed water.     

Impact of full-scale brewing processes on lager beer nitrogen compounds

This paper analyses in a full-scale industrial process firstly the nitrogen compounds in all-malt and in maize-adjunct worts, then their fate during the main brewing steps and finally the influence on them of two different separation technologies: mash filter (Meura 2001) and lauter tun (Steinecker FVAS 26). Data showed that (1) maize-adjunct worts have a lower total nitrogen compounds than all-malt worts; (2) assimilable nitrogen represents 20–24% out of the total nitrogen in both all-malt and in adjunct worts; (3) free amino nitrogen nearly doubles in all-malt compared with adjunct worts; (4) proline and asparagine are the most abundant amino acids in both worts; (5) ammonium disappears during fermentation in wort with the lowest nitrogen content, i.e. in maize-adjunct wort. Moreover, the total nitrogen is reduced in all-malt by 80% with the Steinecker FVAS 26 lauter tun and 25% with the Meura 2001 filter, while in adjunct worts by 87% with the Steinecker FVAS 26 lauter tun and 29% with the Meura 2001 filter. After mash filtration, the content of assimilable nitrogen remains to be adequate for an efficient fermentation, but after lauter tun separation, the assimilable nitrogen reaches values that may compromise the regular fermentation process in both all-malt and adjunct worts. Therefore, when using lauter tun, we have to intervene to reduce its impact on nitrogen compounds and/or plan the wort nitrogen supplementation to overcome the stuck and sluggish fermentations.     

Using rejection thresholds to determine acceptability of novel bioactive compounds added to milk-based beverages

This study aimed to identify the amount of crude casein-hydrolysate (HMW) and a low molecular weight sub-fraction (LMW) thereof that could be incorporated into strawberry- and vanilla-flavoured beverages before the bitterness/taste became objectionable to panellists. The beverages were spiked with increasing amounts of hydrolysate and a 2-alternative forced choice (2-AFC) design was employed to determine rejection thresholds (RjT). Results showed a higher amount of HMW, than LMW, could be incorporated into the beverages before the taste became objectionable and the type of flavouring did not have a significant effect on RjT. Following the 2-AFC, panellists rated the bitterness of the hydrolysates (in water) on a general Labelled Magnitude Scale (gLMS). Results showed no significant differences between the bitterness perception of the HMW and LMW. However, there was considerable variation in the panellists’ perception of bitterness, suggesting possible evidence for segmentation. Using this rationale, each panel was segmented into two groups: those who rated the bitterness of the hydrolysate samples as ≤20 on the gLMS and, those who rated the bitterness as ≥75 on the gLMS, and RjT were examined within them. Although a trend was seen for those most sensitive to bitterness in water, to have a lower acceptance for the level in the beverages, the RjT of the segmented groups were not significantly different from each other. Evaluation of hydrolysates in water does therefore not appear to be suitable for predicting consumer acceptance of hydrolysates in food matrices; highlighting the importance of testing food ingredients in the final food product.     

Using nitrogen isotope fractionation to assess abiotic reduction of nitroaromatic compounds

Compound-specific isotope analysis (CSIA) is an increasingly important tool for the qualitative and quantitative assessment of transformations of organic compounds in contaminated environments. To date, the use of CSIA has been mainly restricted to the elements C and H, although Nconstitutes a very important reactive centerfor many priority contaminants. To evaluate the potential use of N isotope effects in the fate assessment of organic contaminants, we investigated the N isotope enrichment during the abiotic reduction of 4 substituted nitroaromatic compounds (NACs), using two abiotic model reductants, namely Fe(ll) sorbed to goethite (alpha-FeOOH) and juglone (8-hydroxy-1,4-naphthoquinone) in the presence of H2S. Substantial and virtually identical isotope enrichment factors, EpsilonN, of about -30%, indicative of the breaking of one N-O bond, were found for all NACs, regardless of the reductant involved and the substitution of the NAC. These results indicate that the EpsilonN-values determined in our study could be representative for the reduction of aromatic NO2-groups and thus be used to assess the abiotic transformation of NACs qualitatively and quantitatively in complex anoxic environments.     

Soluble, semivolatile phenol and nitrogen compounds in milk-processing wastewaters

Potable water is an essential and major input in processing our food supplies, and the continued growth in food manufacturing is placing increased pressure on this limited resource. Recycling and reuse of factory wastewater can lessen potable water use but requires a detailed understanding of wastewater properties. This study uses solid-phase extraction techniques with gas chromatography-mass spectrometry analysis to investigate trace-level semivolatile organic species in various waste and reference waters associated with the Burra Foods milk-processing plant located in Southeastern Australia. Our focus was on contaminants containing phenolic and heterocyclic nitrogen functional groups, which, because of their toxicity and persistence, may limit options for water recycling and reuse. Effluent from the wastewater treatment plant of the factory showed both the highest soluble carbon burden (47 mg/kg) and concentrations of target compounds. The target species found in these effluents included methyl phenol (13 mg/kg), hydroxy indole (9.8 mg/kg), synthetic tolyltriazoles (5.1 mg/kg) and alkyl phenol ethoxylates (0.2 mg/kg). Given the environmental stability of the tolyltriazoles, they may act as chemical markers where these effluents are used for purposes such as irrigation. Milk evaporator condensate waters, in contrast to the effluent, contained very few target species, with only low levels of pyrrolidine and piperidine derivatives such as ethylglutarimide (450 μg/L) detected. Although there were fewer target microcontaminants overall in the potable and creek reference waters, these samples had characteristic profiles. The potable water analysis revealed hydroxy cineole (2.1 μg/L) and the creek analysis revealed dichlorohydroxyacetophenone (0.3 μg/L), which were not detected in other waters. The compounds found in the wastewaters are likely to have been derived from milk or synthetic chemicals used in factory operations. The presence of nitrogen compounds in all the different milk-processing waters suggest their likely source was milk, probably milk phosphoproteins subjected to thermal, chemical, or microbial degradation. Our benign results for the condensates suggest it may be possible to substitute condensate for potable water with minimal pretreatment, both within the plant and in other applications, such as irrigation of recreation turf.     

麦草氨法预处理制备化机浆工艺的研究

本文研究了尿素-氢氧化钾法,通过使用尿素和氢氧化钾对麦草进行预处理,在控制尿素和氢氧化钾用量、温度、升温保温时间条件下,使麦草化机浆成浆得率达到65%以上。结果表明:在尿素用量9%,KOH用量5%,蒸煮温度160℃、升温时间60min、保温时间60min时,得率为66.72%,所抄纸张的环压强度指数9.43N·m/g、裂断长4..67km、紧度0.53g/cm3,已经达到了瓦楞原纸国家标准(GB/T13023-2008)中A级水平。制浆后的黑液和洗涤液进行酸化和苛化处理,分离出沉渣和上层清液,沉渣作为含钾的有机复合肥料,上层清液用来重新配制蒸煮液。     

Non-protein nitrogen compounds in the higher fungi—A review

The total non-protein nitrogen content and the amounts of individual non-protein nitrogen compounds, as well as factors affecting the amounts of these compounds in the higher fungi, are reviewed. The non-protein nitrogen compounds most significant in this respect are free amino acids, chitin, nucleic acids and urea; however, urea has only a limited occurrence in the higher fungi. In addition to these compounds, nucleotides and related compounds, ammonia, several kinds of amines and quaternary ammonium compounds, volatile nitrogen compounds (other than amines) and nitrogen-containing vitamins are found in the higher fungi.It is widely agreed that misleading information is obtained when the protein content of mushrooms is estimated from the nitrogen content as determined by the Kjeldahl procedure using the conventional 6.25 conversion factor. Possibilities of using a factor other than the 6.25 factor are discussed.     

Substituent effects on nitrogen isotope fractionation during abiotic reduction of nitroaromatic compounds

Compound-specific analysis of nitrogen isotope fractionation is an important tool for assessing transformation pathways of N-containing organic contaminants. We investigated 15N-fractionation during the abiotic reduction of a series of nitroaromatic compounds (NACs) with intrinsic reactivities covering almost 6 orders of magnitude to evaluate substituent effects on 15N kinetic isotope effects, KIEN. Insights into reaction mechanisms and isotopic elementary reactions of NAC reduction were obtained from comparison of experimental results to density-functional theory (DFT) calculations of intrinsic KIEN. Apparent KIEN values for reduction of NACs by structural Fe(II) in octahedral layers of an iron-rich clay mineral were substantial (average +la of 1.038 +/- 0.003), independent of the NACs' reactivity and ring substituent, and larger than reported previously for reduction by Fe(II) species bound to Fe(III)(oxy)hydroxides and mercaptojuglone species (1.031 +/- 0.002). DFT-calculations accounting for semiclassical contributions and quantum-mechanical tunneling yielded a KIEN for N-O bond cleavage between 1.031 and 1.041, showed no substituent effect, and thus agreed well with experimental observations. Calculated transition-state structures of NAC reduction intermediates were consistent with H2O elimination from substituted N,N-dihydroxyanilines as the predominant 15N-fractionating elementary reaction. The absence of substituent effects on the apparent KIEN of NAC reduction may simplify the practical application of 15N-fractionation data for the quantification of contaminant transformation in the environment.     

纯棉织物硼氮协同阻燃的应用研究

研究了在交联剂乙二胺四乙酸二钠,催化剂次亚磷酸钠存在条件下,阻燃剂硼酸在纯棉织物阻燃整理中的应用性能。结果表明,该阻燃剂的优化阻燃整理工艺为:硼酸60 g/L,EDTA二钠20 g/L,次亚磷酸钠20 g/L,用氨水调节pH=4,焙烘温度160℃,焙烘时间3 min。经过整理后的纯棉织物无续燃,具有良好的阻燃性,同时,整理织物的强力损失较小,白度几乎没有损失。     

几种含氮物质对酱油氨基酸态氮及全氮测定值的影响

按GB 18186-2000酱油检测方法测定几种含氮物质的氨基酸态氮值及测定添加了1％这些含氮物质的酱油氨基酸态氮及全氮含量,分析这些含氮物质对酱油测试结果的影响情况,结果表明:无机铵(氯化铵、硫酸铵),有机铵(柠檬酸铵、草酸铵)等均会导致酱油氨基酸态氮测定值偏高,而三聚氰氨和尿素对酱油的氨基酸态氮测定值无影响;以上几种含氮物质均会提高酱油全氮的测定值.     

Utilization of nitrogen compounds in garnacha must inoculated with killer strains of Saccharomyces cerevisiae

 The utilization of nitrogen compounds in garnacha must inoculated with two Saccharomyces cerevisiae killer strains (ICV D47, ICV K1M) was studied. These samples were compared with control must fermented with wild yeast. The results show that in the samples where the inoculated killer yeasts predominated, excretion of amino acids took place from an early stage in the alcoholic fermentation (25% of sugars consumed). This did not occur in the control sample. At the end of the fermentation process, the excretion of amino acids in the samples inoculated with the killer strains was high, so these wines would be considered more unstable from the microbiological point of view. Received: 29 March 1999     

Volatile compounds formation in alcoholic fermentation from grapes collected at 2 maturation stages: influence of nitrogen compounds and grape variety

The aim of this work was to study the influence of nitrogen compounds on the formation of volatile compounds during the alcoholic fermentation carried out with 4 nonaromatic grape varieties collected at 2 different maturation stages. To do this, Monastrell, Merlot, Syrah, and Petit Verdot grapes were collected 1 wk before harvest and at harvest. Then, the musts were inoculated with the same Saccharomyces cerevisiae yeast strain and were fermented in the same winemaking conditions. Amino acids that showed the highest and the lowest concentration in the must were the same, regardless of the grape variety and maturation stage. Moreover, the consumption of amino acids during the fermentation increased with their concentration in the must. The formation of volatile compounds was not nitrogen composition dependent. However, the concentration of amino acids in the must from grapes collected 1 wk before harvest can be used as a parameter to estimate the concentration of esters in wines from grapes collected at harvest and therefore to have more information to know the grape oenological capacity. Application of principal components analysis (PCA) confirmed the possibility to estimate the concentration of esters in the wines with the concentration of nitrogen compounds in the must.