Effect of shaking procedures on the neutral ammonium citrate soluble phosphate fraction in fertiliser materials

The effect of four types of shaker, extraction time and temperature on the quantity of phosphate extracted by neutral ammonium citrate was evaluated at two research laboratories. Six unprocessed phosphate rocks, and five partially acidulated and four fully acidulated phosphate fertilisers were investigated. Compared with the more than 10-fold variation in the solubility of the two reactive phosphate rock materials, Sechura and North Carolina, that resulted from using different types of shaker, the solubility of the unreactive phosphate rock materials and the partially and fully acidulated phosphate fertilisers in citrate was influenced to a much smaller degree by the action of the shaker. Sechura was less soluble in citrate that all four unreactive phosphate rock materials when either of the two horizontal shakers were used. This is totally at odds with the documented differences in the chemical reactivity' and agronomic effectiveness of these phosphate rock materials. Not until a wrist-action shaker was used did the solubility of Sechura and North Carolina exceed that of the unreactive materials and approach that obtained with a full end-over-end shake. The neutral ammonium citrate procedure needs to include a more precise definition of the type of shaker and its speed. In laboratories where temperature-controlled extraction is not available, a 24-h shake at 20°C using an orbital or end-over-end apparatus could be an alternative to the standard 1-h extraction at 65°C.     

Chemical and physical characteristics of phosphate rock materials of varying reactivity

Several chemical and physical properties of 10 phosphate rock (PR) materials of varying reactivity were evaluated. These included North Carolina phosphate rock (NCPR), Sechura phosphate rock (SPR), Chatham Rise phosphorite (CRP), Arad phosphate rock (APR), Gafsa phosphate rock (GPR), North Florida phosphate rock (NFPR), Jordanian phosphate rock (JPR), Mexican phosphate rock (MPR), Nauru Island phosphate rock (NIPR), and Makatea Island phosphate rock (MIPR). Concentrations of As and Cd were highest in NCPR and U was higher in APR and CRP than in the other reactive PR materials. Because Cd and U can accumulate in biological systems, it may be necessary to direct more attention towards the likely implications of Cd and U concentrations when evaluating a PR for direct application. Three sequential extractions with 2% citric acid may be more useful for comparing the chemical solubility of PR materials, particularly for those containing appreciable CaCO₃. For each particle-size fraction from <63 to >500 μm, SPR was more soluble in 2% citric acid than was NCPR. The higher solubility of SPR than NCPR in 2% citric acid, 2% formic acid, and neutral ammonium citrate possibly results from a higher chemical reactivity rather than from any difference in the surface area presented for dissolution. The poor relationship obtained between surface area and the solubility of the PR materials in the three chemical extractants suggests that surface area plays a secondary role to chemical reactivity in controlling the solubility of a PR in a chemical extractant. A Promesh plot provided an effective method for describing the particle-size characteristics of those PR materials which occurred as sands. Fundamental characteristics, such as mean particle size and uniformity, can readily be determined from a Promesh plot.     

Inhibitory activity of phosphates on molds isolated from foods and food processing plants

Six commercial phosphates were evaluated for inhibition of the growth of 17 molds isolated from food sources. The assays were performed at neutral and natural (without pH adjustment) pH values, and the molds were streaked on plate count agar with added phosphates. Phosphate concentrations of 0.1, 0.3, 0.5, 1.0, and 1.5% (wt/vol) were used, and the MIC was determined. The resistance of molds to phosphates depended on the species. At a neutral pH, Aspergillus ochraceus and Fusarium proliferatum were resistant to all phosphates at all concentrations assayed, and Byssochlamys nivea, Aureobasidium pullulans, and Penicillium glabrum were most sensitive. The most inhibitory phosphates were those with chain lengths greater than 15 phosphate units and the highest sequestering power. At natural pH values (resulting from dissolving the phosphate in the medium), inhibitory activity changed dramatically for phosphates that produced alkaline or acidic pH in the medium. Phosphates with alkaline pH values (sodium tripolyphosphate of high solubility, sodium tripolyphosphate, and sodium neutral pyrophosphate) were much more inhibitory than phosphates at a neutral pH, but sodium acid pyrophosphate (acidic pH) had decreased inhibitory activity. The results indicate that some phosphates could be used in the food industry to inhibit molds linked to food spoilage.     

Effects of citrate and NaCl on size, morphology, crystallinity and microstructure of calcium phosphates obtained from aqueous solutions at acidic or near-neutral pH

Precipitation of calcium phosphates occurs in dairy products and depending on pH and ionic environment, several salts with different crystallinity can form. The present study aimed to investigate the effects of NaCl and citrate on the characteristics of precipitates obtained from model solutions of calcium phosphate at pH 6·70 maintained constant or left to drift. The ion speciation calculations showed that all the starting solutions were supersaturated with respect to dicalcium phosphate dihydrate (DCPD), octacalcium phosphate (OCP) and hydroxyapatite (HAP) in the order HAP>OCP>DCPD. X-ray diffraction (XRD) and Fourier transform infrared (FTIR) analyses of the precipitates showed that DCPD was formed at drifting pH (acidic final pH) whereas poor crystallised calcium deficient apatite was mainly formed at constant pH (6·70). Laser light scattering measurements and electron microscopy observations showed that citrate had a pronounced inhibitory effect on the crystallisation of calcium phosphates both at drifting and constant pH. This resulted in the decrease of the particle sizes and the modification of the morphology and the microstructure of the precipitates. The inhibitory effect of citrate mainly acted by the adsorption of the citrate molecules onto the surfaces of newly formed nuclei of calcium phosphate, thereby changing the morphology of the growing particles. These findings are relevant for the understanding of calcium phosphate precipitation from dairy byproducts that contain large amounts of NaCl and citrate.     

Sorption and desorption of Cd2+ and Zn2+ ions in apatite-aqueous systems

As a low-soluble phosphate mineral capable of binding various metal ions, apatite can be used to immobilize toxic metals in soils and waters. In the present research the factors affecting sorption and desorption of Cd2+ and Zn2+ ions on/from apatites are investigated. Batch experiments were carried out using synthetic hydroxy-, fluoride-, and carbonate-substituted apatites having various specific surface area (SSA). Apatite sorption capacity was found to depend mainly on its SSA, ranging from 16 to 78 and from 11 to 79 mmol per 100 g of apatite for Cd2+ and Zn2+, respectively. The solution composition (pH, and presence of Cl- and NO3- ions) had no essential impact on sorption. Desorption of bound cations depended both on the sorption level and solution composition. The amount of desorbed Cd2+ and Zn2+ increased proportionally to the amount of sorbed cations. However, apatites having higher sorption capacity release relatively less sorbed cations. Desorption increases with increasing Ca2+ concentration in the solution, reaching 8-20% of sorbed Cd2+ in 0.002 M, 10-35% in 0.01 M, and 33-45% in 0.05 M Ca(NO3)2 solution. Compared to nitrate solutions, the presence of Cl- ions in the solution promotes the release of bound cations. Desorption of Zn2+ is slightly higher than that of Cd2+. The desorption mechanism was assumed to include both ion-exchange and adsorption of Ca2+ ions on apatite surface.     

Release of bound iron and aluminium from soils by the root exudates of tea (camellia sinensis) plants

Root exudate of young tea plants contained appreciable quantities of malic acid. Malic acid was capable of solubilising P, Fe and Al from rock phosphate fertiliser. Tea soils incubated with added malic acid released appreciable quantities of P, Fe and Al. In tea soils where most of the P added as the rock phosphate is immobilised as the iron and aluminium phosphates, malic acid may prove to be useful in chelating these elements and so releasing the phosphates for utilisation by the tea plant.     

Investigation of the clay mineral protection theory for non-hydrolysable nitrogen in soil

The stability of clay minerals and synthetic clay mineral-nitrogen complexes in boiling 6 N hydrochloric acid was studied to determine whether clay minerals in soil could protect nitrogen compounds or ions from solution. The crystal structure of uncomplexed clay minerals, such as montmorillonite, appeared to be destroyed by boiling acid. Interlamellar ammonium did not reduce the solubility of these clay minerals in boiling acid, nor was the ammonium ion protected from solution. However, a number of organic nitrogen compounds (in particular quaternary ammonium salts) markedly reduced the solubility of montmorillonite. In addition the clay mineral reduced the solubility of organic nitrogen compounds in boiling acid. This reduction in solubility did not appear to be due to humin formation or to adsorption of nitrogen compounds on the amorphous residue produced from acid treatment of montmorillonite. The results suggest that a clay mineral protection theory for non-hydrolysable nitrogen is tenable.     

Borbestimmung in Fuerschutzsalzen

Boron compounds, like boric acid and borates are, apart from ammonium phosphates essential for fire protection, the main composites of most fire protective salts. They reinforce the fire retardant effect of the phosphates; moreover they offer effective protection against insects and various species of fungi. The quantitative determination of boron is therefore an essential part of every fire salts analysis.     

Purification and properties of an acid phosphatase from lactating bovine mammary gland

An acid phosphatase was partially purified from the cytosol of lactating bovine mammary gland by precipitation with ammonium sulfate and protamine, chromatography on carboxymethyl cellulose, and gel filtration on Sephadex G-75. The enzyme hydrolyzed aromatic phosphates but was less active toward alkyl phosphates, ATP, and phosphoproteins (casein and phosvitin). A sulfhydryl group seems to be essential for activity, since dithiothreitol and cysteine activated the enzyme; compounds that react with the sulphydryl groups in proteins were inhibitory. Orthovanadate, phosphate, and zinc ions also inhibited the phosphatase.     

柠檬酸钠协同碳酸氢钠替代磷酸盐对法兰克福香肠品质的影响

为减少磷酸盐在肉类加工中的使用,降低乳化肉糜制品中磷酸盐的含量,开发高效的无磷保水剂正逐步成为肉品行业的研究热点.本研究在添加0.2％(w/w)碳酸氢钠的基础上,将柠檬酸钠分别以0.1％、0.15％、0.2％、0.25％和0.3％(w/w)的添加量与碳酸氢钠进行复配,利用其替代传统的磷酸盐,探究其对乳化肉糜制品(以法兰...     

Gelling properties of whey protein isolate: influence of calcium removal by dialysis or diafiltration at acid or neutral pH

Dialysis of whey protein isolates (WPI) removed much more calcium when carried out at an acid pH (close to 4.0) than at neutral pH. Diafiltration at acid pH was also effective. The characteristics of thermally-induced gels prepared from WPI dialysed at acid or neutral pH were studied at pH 3.75 or pH 7.0, respectively, and at calcium concentrations ranging from 0 to about 60mM (with addition of calcium chloride). The water-holding capacity (WHC) and elasticity of gels increased with decreasing calcium concentration, at both pHs. Gel firmness was maximum at 10–20 mM calcium. The solubility of the protein constituents of WPI gels in a pH 8.0 buffer was high in the case of acid gels (especially at calcium concentrations lower or equal to 20 mM) and low for neutral gels at all calcium concentrations. Protein solubility values in the presence or absence of denaturing and reducing agents reflect the existence of intermolecular disulphide bonds in neutral gels and their absence in acid gels.     

产叶酸菌株的筛选及其发酵条件的优化

从土壤样本中筛选分离得到的菌株R-1和S-1具有产叶酸的能力,进行单因素实验和正交分析,优化碳源、氮源、初始pH、发酵时间等条件,叶酸产量提高约为10%;加入前体物质对氨基苯甲酸(PABA),菌株R-1和S-1产叶酸的能力显著提高,分别提高了2倍和1.8倍;最后进行正交分析得出各菌种的最佳发酵产叶酸的因素选择。结果显示,菌株R-1的最佳产叶酸条件是葡萄糖25g/L,柠檬酸铵4g/L,PABA0.3g/L,接种量2%,培养时间24h,初始pH6.5,叶酸产量达到了1.92μg/mL;菌株S-1最佳产叶酸条件是蔗糖20g/L,柠檬酸铵2g/L,PABA0.3g/L,接种量3%,培养时间48h,初始pH5.5,叶酸产量为1.31μg/mL。     

不同保水剂对可微波预油炸鸡肉串品质的影响

针对可微波预油炸鸡肉串加工工艺,考察了不同保水剂对产品品质的影响.选用卡拉胶、变性淀粉、柠檬酸钠作为混合磷酸盐的替代物,通过单因素和正交试验,得出变性淀粉对肉品的保水性影响最大,卡拉胶次之,柠檬酸钠最小,三者的最佳配比是卡拉胶质量分数为0.05%,变性淀粉质量分数为0.30%,柠檬酸钠质量分数为0.05%,与最佳配比条件下的复合磷酸盐相比,两者的持水效果基本相同.但在相同的冻藏条件下,添加无磷保水剂的肉品微波失水率显著低于添加磷酸盐保水剂的肉品,无磷酸保水剂的添加使肉品在长时间冻藏后依然具有较好的持水能力.     

酶水解大豆蛋白物理化学性质的综合表征

大豆分离蛋白分别用AS1.398中性蛋白酶和黑曲霉3.4310酸性蛋白酶在不同条件下水解后,测定其水解度(DH)、三氯乙酸(TCA)溶解度、等电点(IP)溶解度,以及不同分子量区段的相对含量等13个参数.通过主成分分析将这些参数线性组合为4个主成分,但是中性蛋白酶和酸性蛋白酶水解产物参数在主成分中的组合方式不同.以主成分为指标对全体样品进行聚类分析时,两种酶水解产物各自聚为一类;中性蛋白酶和酸性蛋白酶的水解产物单独进行聚类分析则分别得到5个和4个子类,其中包括水解条件差别较大的水解产物,说明水解工艺参数之间存在某种协同或互补效应.     

Fractionation and partial characterization of non-pectic polysaccharides from yellow mustard mucilage

A polysaccharide fraction was isolated from yellow mustard mucilage using pectinase hydrolysis and ammonium sulphate precipitation. Results indicated that ammonium sulphate precipitation produced a material with more glucose and less uronic acid compared to ethanol precipitation. Chemical, structural and rheological properties of the isolated fraction were investigated. Chemical analysis revealed that this material was mainly composed of glucose (61.1%); however, other sugars were also found, including galactose (13.8%), rhamnose (4.5%), mannose (13.1%) and xylose (7.5%). It also contained 6.9% of uronic acid. Methylation analysis indicated that this polysaccharide fraction consisted mainly of a β-1,4 linked glucosyl backbone. Rheological tests showed that the polysaccharide exhibited strong shear-thinning flow behaviour and weak gel structure. When the aqueous weak gel solution was subjected to an acid environment, the gel structure became stronger compared to more neutral conditions. This polysaccharide exhibited thermal stability over the temperature range from 5 to 90 °C.     

钠盐对果汁豆奶稳定性的影响

采用单因素实验及正交实验分别研究了单个磷酸盐、柠檬酸盐及复合磷酸盐等含钠离子的不同盐类豆奶稳定性的影响。结果表明,钠类盐的加入能使体系的粘度及稳定性升高,但其添加量有最佳值,此值因盐的种类不同而不同;柠檬酸三钠的稳定效果优于单个的磷酸盐,但不如复配磷酸盐。加入柠檬酸三钠和复合磷酸盐后,果汁豆奶中的平均粒径均表现出增大的趋势。     

磷酸酯淀粉的制备

选用磷酸氢二钠、磷酸二氢钠、焦磷酸钠及混合磷酸盐作酯化剂制备了木薯磷酸酯淀粉,考察了酯化剂用量、磷酸盐混合物的质量比、尿素等因素对磷酸酯淀粉的取代度和反应效率的影响.结果表明:磷酸酯淀粉的取代度随磷酸盐的用量增加而增大,磷酸盐的结构影响其作用效果.磷酸盐混合物作酯化剂的效果较纯磷酸盐好.添加适量的尿素可提高淀粉的酯化速率和磷酸盐的反应效率.磷酸酯淀粉的取代度对粘度影响不大,但其溶解度是随着取代度的增大而增大.     

Inactivation of calcium-dependent lactic acid bacteria phages by phosphates

The capacity of three phosphates to interrupt the lytic cycle of four specific autochthonal bacteriophages of lactic acid bacteria used as starters was assayed. The phosphates used (polyphosphates A and B and sodium tripolyphosphate-high solubility [TAS]) were selected on the basis of their capacity to sequester divalent cations, which are involved in the lytic cycle of certain bacteriophages. The assays were performed in culture media (deMan Rogosa Sharpe and Elliker broths) and reconstituted (10%, wt/vol) commercial skim milk to which phosphates had been added at concentrations of 0.1, 0.3, and 0.5% (wt/vol). Phosphate TAS was the most inhibitory one, since it was able to inhibit the lytic cycle of all bacteriophages studied, in both broths and milk. In broth, polyphosphates A and B inhibited the lytic cycle of only two bacteriophages at the maximal concentration used (0.5%), whereas in milk, they were not capable of maintaining the same inhibitory effect.     

Phosphate and Modified Beef Connective Tissue Effects on Reduced Fat, High Water-added Frankfurters

The effects of acidic, neutral and alkaline phosphates and amounts of modified beef connective tissue (0, 10 or 20%) were determined on the characteristics of 20% fat/20% water-added frankfurters or 10% fat/30% water-added frankfurters. Processing yields were lowest in both formulations with acidic phosphate. Cured meat color intensity was higher with the acidic phosphate than with alkaline or neutral phosphates. Alkaline or neutral phosphate samples partially recovered losses in emulsion stability that had occurred due to connective tissue level. The addition of 20% connective tissue improved processing yields and decreased cohe-siveness of 10% fat/30% water added frankfurters. Connective tissue addition had no effect on microbial stability. Acidic phosphates might be more effective in direct treatment of high collagen materials in a preblend rather than in direct addition into a frankfurter formulation.     

提高山梨酸及钾盐防腐效果的研究进展

山梨酸在人体内能参加正常的新陈代谢,是迄今为止国际公认最好的食品防腐剂之一。山梨酸是酸性防腐剂,不易溶于水,且在中性条件下,抑菌效果差;而常用的山梨酸钾在水中的溶解性好,但在酸性条件下很难形成真正具有抑菌作用的山梨酸分子。本文主要介绍了目前国内外对提高山梨酸及钾盐防腐效果的研究进展。