低粘度磷酸酯淀粉浆料与递质pH的依赖关系

在pH值为2．0～7．0范围内，制备不同的样品，以粘度、粘度稳定性、浆膜性能及浆液粘附性能为量化指标，研究了磷酸酯淀粉粘度与制备递质的pH依赖关系．结果表明，起始pH值对粘度的影响较显著，pH值范围不同，影响程度和方式也不同，当pH≤4．0时，粘度降低较快，主要发生淀粉链水解，浆膜性能及浆液粘附性较差；pH≥6．0，淀粉开始发生交联，粘度逐渐增加、稳定性降低；4．8≤pH≤5．4，淀粉水解适中，能获得粘度、浆膜性能及浆液粘附性较好的磷酸酯淀粉，尤以pH=5．2为优；在该pH值范围内，未观察到粘度稳定性与pH较明显的规律性变化关系．     

The role of calcium, phosphate and citrate ions in the stabilization of casein micelles.

To obtain greater insight into the interaction of Ca, citrate and phosphate ions with casein, 31PNMR measurements were performed on combinations of these ions with alphas- and kappa-caseins. It was found that addition of alphas-casein to a Ca phosphate solution in D2O at 27 degrees C and pD 6.4 resulted in a downfield shift of the 31P singlet. An almost identical shift was observed with kappa-casein, but no shift was found when only phosphate ions were present or when Ca2+ were added to phosphate ions in the absence of casein. Separate experiments with poly-L-lysine, mol. wt approx. 35,000, resulted in similar downfield 31P chemical shifts of Ca phosphate as with both caseins, whereas no shift was observed when poly-glycine was added. From these results it can be concluded that Ca and phosphate ions associate with casein in a co-operative manner, probably in the way described by ter Horst (1963) as a complex with the NH3+-groups of lysine or arginine in a structure such as: (casein--NH3+)--PO43---Ca2+. The formation of this complex may be enhanced by citrate ions, since preliminary results have shown that addition of Na citrate to a solution of alphas-casein with added Ca phosphate produces a broadening of the 31P signal as well as a chemical shift.     

X52管线钢抗硫化氢应力腐蚀实验分析

介绍X52管线钢的抗硫化氢应力腐蚀实验。根据NACE 0284—2003和NACE TM 0177—2005,采用氢致开裂(HIC)实验,硫化物应力腐蚀(SSC-A,SSC-四点弯曲法)实验和电化学测试,检测X52管线钢的抗硫化氢应力腐蚀(SSC)开裂能力。将X52管线钢经过96 h的氢致开裂实验,加载比例分别为最小屈服强度的80%,85%,90%的SSC-A实验和SSC-四点弯曲实验720 h,均未发现裂纹。结果表明,X52管线钢具有较好的抗硫化氢应力腐蚀能力。     

2,4-D sorption in iron oxide-rich soils: role of soil phosphate and exchangeable Al

This study examined herbicide retention in iron oxide-rich variable charge soils (Ultisols) under no cultivation (forest), agriculture (farm), and turf maintenance (golf course) to explore the following hypothesis: inorganic phosphate accumulation from soil fertilization and liming to decrease exchangeable aluminum (Al) content will influence carboxylic acid herbicide sorption onto soils and leaching into groundwater. A suite of soil properties, including mineralogy (particularly soil iron and aluminum oxide content), exchangeable Al content, and soil phosphate content, influenced sorption of the anionic, 2,4-D. In general, 2,4-D sorption was lower in the presence of phosphate, possibly due to competition between phosphate and 2,4-D for surface sites or increase in surface negative charge resulting from phosphate sorption. Additionally, 2,4-D sorption was greater in the presence of exchangeable Al. It appears that 2,4-D may form surface complexes with or be electrostatically attracted to exchangeable aluminum in the soil. Our results suggest that carboxylic acid herbicides may be more easily leached in intensively managed Ultisols subject to continued phosphate fertilization and liming.     

Effects of pithing on pH, creatine phosphate and ATP-related compounds of beef Psoas major and Longissimus dorsi muscles

The effects of pithing at slaughter on meat quality were studied in M. longissimus dorsi (LD muscle) and M. psoas major (PM muscle) from steers. Ten steers, half of them pithed and the others not pithed at slaughter, were used for determining pH values and concentrations of creatine phosphate (CP), adenosine triphosphate (ATP) and its breakdown products in the muscles at 2·0 h post mortem. CP was not detected in any PM muscles from pithed steers and no significant differences were observed between pithed and non-pithed steers on the mean values of pH and any compounds, but significant differences were observed in the variance of pH value, ATP, (inosine monophosphate IMP) and inosine levels in PM muscles and of (adenosine diphosphate ADP) and IMP levels in LD muscles. When two steers with excitable temperament were excluded from the pithed group significant differences of variance between the treatments were observed only in PM muscles. The pithing procedure thus affects the levels of pH and of some of the ATP-related compounds in the PM but not in LD muscles.     

Effects of pH and phosphate status of a silty clay loam on manganese,zinc and copper concentrations in soil fractions and in clover

The field pH of a silty clay loam soil affected manganese, zinc and copper concentrations in the fraction extracted by DTPA; lower pH soils had higher metal concentrations. The soil pH also affected manganese and zinc but not copper concentrations in the soil solution, and in shoots of clover grown in pots. Metal concentrations in soil fractions were not affected by soil phosphate status, but zinc and copper concentrations in clover shoots were significantly lower when plants were grown on soils of high phosphate status. Manganese and zinc levels in shoots were predicted slightly more accurately by using soil solution data than by using concentrations extracted by DTPA.     

The effect of phosphate, sodium chloride, sodium nitrite, storage temperature and pH on the growth of enteropathogenic Escherichia coli in a laboratory medium

The effect of eight phosphates in combination with sodium chloride/nitrite mixtures on growth of mixed strains of enteropathogenic Escherichia coli over a period of 10 weeks at three pH values (5.6, 6.2, 6.8) and at seven temperatures ranging from 10 degrees C to 35 degrees C is reported. All eight phosphates inhibited growth to varying degrees in at least some of the conditions investigated. Instances of inhibition increased with concentration of sodium chloride/nitrite and were more frequent at lower temperatures and pH values.     

Effects of pH and sodium ions on NaHCO3 extractable phosphate in calcareous/sodic soils

One calcareous and one sodic soil were treated with solutions of either sodium carbonate (Na₂CO₃) or sodium perchlorate (NaCIO₄) to increase their sodium (Na) saturation before extracting with sodium bicarbonate (NaHCO₃) to measure the recovery of native plus added phosphate (P). The Na₂CO₃ additions also increased pH, and by comparing with the NaCIO₄ treatments, it was possible to separate the effects of added Na and pH on extractable P. For the calcareous soil both added Na and increased pH led to increases in the amount of NaHCO₃-extractable P. For the sodic soil the amount of extractable P was mainly affected by pH, with little, if any, effect of the added Na. The suitability of the Olsen test for soil P for Na-affected soils is discussed.     

The effect of cooking temperature on the functional properties of beef proteins: The role of ionic strength, pH, and pyrophosphate

This study examined the effect of ionic strength (0·12 to 0·52), pH (5·50 and 6·00), pyrophosphate (PP) concentration (0 and 0·31%) and cooking temperature (52 to 87°C) on the cook yield (CY) and tensile strength (TS) of beef homogenates. Increasing the ionic strength, pH and pyrophosphate concentration increased the temperature at which cooking loss first occurred and decreased the temperature required for maximum TS. For most treatments, ionic strengths between 0·32 and 0·42 prevented cooking loss at all temperatures; the lower ionic strengths were required at the higher pH and PP concentration. Maximum TS occurred at 66°C for treatments that had no cooking loss between 60° and 75°C. For treatments that had cooking loss in this temperature range, TS increased linearly with increasing temperature; however, the TS values of these treatments were much lower than those in the former category. CY and TS were optimized by heating to 66°C. PP had a positive effect on both functional properties at ionic strengths >0·25 but a negative effect at ionic strengths <0·25.     

Influence of pH,concentration of sodium lactate as an additive and ultrasonic treatment on synthesis of zinc phosphate white pigments

Zinc oxide that has the photocatalytic activity is used as a white pigment for cosmetics. A certain degree of sebum on the skin is decomposed by the ultraviolet radiation in sunlight. In this work, zinc phosphates were prepared from zinc nitrate and phosphoric acid at pH 5 and 7 with and without the addition of sodium lactate and ultrasonic treatment as a novel white pigment for use in cosmetics. The chemical composition, powder properties, photocatalytic activity, colour phase, moisture retention and smoothness of the zinc phosphates were studied. The obtained materials had a Zn/P ratio of about 1.5, which corresponds to zinc orthophosphate Zn₃(PO₄)₂. Samples prepared with ultrasonic treatment indicated the high ratios of large particles in scanning electron microscopy images and particle‐size distributions. The photocatalytic activity of these zinc phosphate particles was too less to protect the sebum on the skin. The materials obtained and their thermal products at 100°C showed a high reflectance within the range of visible light. The slipping resistance and roughness of the powder were enough low for use in cosmetics.     

Oxygen isotopes unravel the role of microorganisms in phosphate cycling in soils

Phosphorus (P) is considered the ultimate limiting nutrient for plants in most natural systems and changes in the distribution of inorganic and organic P forms during soil development have been well documented. In particular, microbial activity has been shown to be an important control on P cycling but its contribution in building up the pool of plant-available P during soil development is still poorly quantified. To determine the importance of different biological processes on P cycling, we analyzed the isotopic composition of oxygen in phosphate (δ(18)O-Pi) from the parent material, soil microorganisms, the available P pool, and from the vegetation along a 150-year soil chronosequence of a glacier forefield. Our results show that at all sites, δ(18)O-Pi of microbial Pi is within the range expected for the temperature-dependent equilibrium between phosphate and water. In addition, the isotopic signature of available Pi is close to the signature of microbial Pi, independently of the contribution of parent material Pi, vegetation Pi or Pi released from organic matter mineralization. Thus, we show that phosphate is cycled through soil microorganisms before being released to the available pool. This isotopic approach demonstrates for the first time in the field and over long time scales, and not only through controlled experiments, the role of the microbial activity in cycling of P in soils.     

Combined effects of NaCl and raw meat pH on water-holding in cooked sausage with and without added phosphate

The intake of sodium in diets is of concern in many industrialized countries. Attempts have been made to lower sodium intake via meat products. The keeping quality, taste and water-holding/firmness of meat products have usually been impaired. The water-holding in cooked sausage was determined by a laboratory sausage method. Beef and pork with varying natural post-rigor pH-values (range: pork 5.50-6.12 and beef 5.60-6.48) were used as mixtures, and 0.5-2.5 % NaCl was used with or without added commercial sausage phosphate (2,5 g/kg determined as P(2)O(5)). The pH-values of raw batter increased to a level 0.0-0.7 units higher than the pH-values of the respective meat mixtures. The increase was higher in lower pH-values, with higher salt levels and with added phosphate. The cooking caused an additional increase of about 0.0-0.2 units, and the increase was again higher at lower pH-values. Maximum in water-holding was reached in 2.5% NaCl in all pH-values, both with and without added phosphate. The pH-value of meat raw materials for the maximum water-holding was ca. 6.3. The combined effect of salt and pH is important in high salt contents and low pH-values. By 2.5% NaCl , where the maximum in water-holding was obtained, raw meat pH has the largest effect, but in low NaCl contents, below 1.0%, only a minor effect in pH-values below 5.9, and above that, almost no effect. Approximately the same water-holding as with 2.5% NaCl in pH 5.7 can be reached with 1.5% NaCl in pH 6.1 and above. The effects of the variables were similar with pork and beef. It was concluded that when lowering the salt content in cooked sausages, the pH of the batter should be increased by using high-pH meat mixtures and/or pH-raising phosphates in order to reach a high enough level of water-holding.     

Sorption of three tetracyclines by several soils: assessing the role of pH and cation exchange

Tetracyclines (TCs) are widely used in veterinary medicine for treatment and prevention of disease and are present in animal waste products. Detection of TCs in soil, sediments, and water, and the growing concern of their potentially adverse effect on natural ecosystems have resulted in a need to understand their behavior in aqueous soil systems. TCs have multiple ionizable functional groups such that at environmentally relevant pH values, they may exist as a cation (+ 0 0), zwitterion (+ - 0), or a net negatively charged ion (+ - -), which complicates predicting their sorption, availability, and transport. We investigated the sorption of oxytetracycline (OTC), tetracycline (TC), and chlortetracycline (CTC) by several soils varying in pH, clay amount and type, cation exchange capacity (CEC), anion exchange capacity (AEC), and soil organic carbon in 0.01 N CaCl2, 0.001 N CaCl2, and 0.01 N KCI. All three TCs are highly sorbed, especially in acidic and high clay soils. When normalized to CEC, sorption tends to decrease with increasing pH. A sorption model in which species-specific sorption coefficients normalized to pH-dependent CEC (Kd+00, kd+-0, and kd+--) and weighted by the pH-dependent fraction of each species fit the data well across all soils except for a soil rich in gibbsite and high in AEC. Resulting kd+00 values were more than an order of magnitude larger than values for either kd+0 and kd+--values such that kd+00 alone described most of the sorption observed as a function of pH for eight soils that varied in their mineralogy and pH (pH ranged from 4 to 8).     

Effects of pre-rigor injection of sodium citrate or acetate, or post-rigor injection of phosphate plus salt on post-mortem glycolysis, pH, and pork quality attributes

Forty pork carcass sides were assigned to one of four treatments: pre-rigor citrate (CIT) or acetate injection (ACE); post-rigor phosphate and salt injection (PHOS); and non-injected control (CON). Loins in 20 sides were injected at 50 min post-mortem with 4% solutions of CIT or ACE to approximately 110% of projected loin weights, and 10 loins were injected at 24 h post-mortem to 106.6% with a solution of 4.4% PHOS and 2.2% salt. Although CIT increased pH (P < 0.05), neither CIT nor ACE altered (P > 0.05) glycolytic metabolite concentrations. The pH increase in muscles from the CIT treatment was most likely due to its buffering ability rather than to its glycolytic inhibition. Pre-rigor CIT injection improved tenderness without the detrimental effects on color or flavor found with PHOS, but neither CIT nor ACE altered glycolytic metabolites or improved firmness, wetness, or fresh visual color over CON. Poor flavor attributes of the ACE treatment will hinder its use as an ingredient for pork enhancement solutions.     

Effects of pre-rigor injection of sodium citrate or acetate,or post-rigor injection of phosphate plus salt on post-mortem glycolysis,pH, and pork quality attributes

Forty pork carcass sides were assigned to one of four treatments: pre-rigor citrate (CIT) or acetate injection (ACE); post-rigor phosphate and salt injection (PHOS); and non-injected control (CON). Loins in 20 sides were injected at 50 min post-mortem with 4% solutions of CIT or ACE to approximately 110% of projected loin weights, and 10 loins were injected at 24 h post-mortem to 106.6% with a solution of 4.4% PHOS and 2.2% salt. Although CIT increased pH (P < 0.05), neither CIT nor ACE altered (P > 0.05) glycolytic metabolite concentrations. The pH increase in muscles from the CIT treatment was most likely due to its buffering ability rather than to its glycolytic inhibition. Pre-rigor CIT injection improved tenderness without the detrimental effects on color or flavor found with PHOS, but neither CIT nor ACE altered glycolytic metabolites or improved firmness, wetness, or fresh visual color over CON. Poor flavor attributes of the ACE treatment will hinder its use as an ingredient for pork enhancement solutions.     

Effect of iron chelates on oil–water interface,stabilized by milk proteins: The role of phosphate groups and pH. Prediction of iron transfer from aqueous phase toward fat globule surface by changes of interfacial properties

Iron incorporated into food systems induces oxidation and precipitation. The consequences are reduced bioavailability and a functional modification of other food components such as proteins. The iron-chelates such as ferrous bisglycinate represent a possibility to avoid side effects, since the iron is protected. The aim of this study is to investigate the effects of iron-chelates compounds on the properties of an oil/water interface stabilized by caseinate or β-lacotoglobulin, under environmental conditions at 20 °C. Analyses were performed using dynamic drop tensiometry during 5000 s. The aqueous bulk phase is an imidazole/acetate buffer (0.1 M), containing 0.4 × 10⁻⁶ M protein, and 0.2 × 10^-6 9 M iron-chelates compounds. The results indicate that, under neutral conditions, the addition of some irons salts (NaFe-EDTA or Fe-bisglycinate) do not change the structure of the interface stabilized by a protein containing no phosphate groups (β-lactoglobulin). In the case of caseinate, NaFe-EDTA addition increases the lowering rate of surface tension at pH 6.5. On the contrary, the lowering rate of surface tension with caseinate is inhibited by Fe-bisglycinate at pH 6.5. Such an effect is not observed with β-lactoglobulin. The low transfer of irons ions from the bulk to the interface stabilized by β-lactoglobulin is confirmed by zetameter and FTIR measurements. These results indicate an effective strategy to follow for controlling the physical and chemical stability of an emulsion stabilized with proteins.     

Correlation of 2-chlorobiphenyl dechlorination by Fe/Pd with iron corrosion at different pH

The rate of 2-chlorobiphenyl dechlorination by palladized iron (Fe/ Pd) decreased with increasing pH until pH > 12.5. Iron corrosion potential (Ec) and current (jc), obtained from polarization curves of a rotating disk electrode of iron, followed the Tafel equation at pH < or = 5.5 and pH > or = 9.5. The pH dependence of the dechlorination rate constant (k1) suggests four pH regimes. In the low pH regime (3-5.5), /Ec/ and je decreased with increasing pH and k1 was linearly correlated to /Ec/ and jc0.5. The correlation between k1 and jc0.5 indicates direct involvement of active hydrogen species (on the Pd surface) in PCB dechlorination. In the mid pH regime (5.5-9.5), no significant effect of pH was evident on the values of k1, je, and Ec, a combined result of limiting anodic oxidation of iron to an intermediate product (iron hydroxide) and a proton-independent overall reaction. Both /Ec/ and jc increased significantly as pH increased from 9.5 to 14. A cleartrough of the k1 values in solutions of pH between 12 and 13 and the mismatch between the kinetic and corrosion data suggest two pH regimes (9.5-12.5 and 12.5-14) of different corrosion mechanisms.