Effect of lime on the dissolution of two phosphate rocks in acid soils

The effect of pH and calcium (Ca) on the dissolution of Gafsa (GPR) and Christmas Island A (CIPR) phosphate rocks (PR) was examined in closedincubation and open-leaching systems in six acid, Malaysian soils. The pH of the soils was increased to between 4.5 and 6.1 by incubating with calcium carbonate (CaCO₃); soil was also incubated with calcium chloride (CaCl₂) to provide equivalent amounts of Ca without causing any marked change in pH. In the closed-incubation system, dissolution of reactive GPR was overall higher (11–70%) than for the less reactive CIPR (12–43%) after 60 days of incubation. Dissolution of PR decreased with increasing levels of CaCO₃ or CaCl₂, but the decrease was more pronounced in CaCO₃-treated than in CaCl₂-treated soils. Increasing additions of CaCl₂ decreased the size of the available sink for Ca from 84.0 to 0 mmol (+) kg^–1 soil. Although the addition of CaCO₃ increased the cation-exchange capacity (CEC) of these variable-charge soils (from 23.0 to 199.0 mmol (+) kg^–1 soil), most of the newly-created exchange sites were occupied by Ca added through CaCO₃. This was responsible for the decrease in size of the sink for Ca. Addition of CaCO₃ also decreased the proton supply from 260.7 to 0 mmol (+) kg^–1 soil, which in conjunction with the decrease in size of the Ca sink decreased the dissolution of PR. The effect of CaCO₃ and CaCl₂ on PR dissolution varied between soils and was related to pH-buffering and the Ca-sink size. In an open-leaching system, large amounts of Ca (8–40%) added as CaCO₃ were removed in the leachate and hence the decrease in GPR dissolution with CaCO₃ addition was less in the open-leaching than in the closed-incubation system.     

粮油食品中微生物和真菌毒素污染预测模型研究进展

粮油食品供应链环节多,危害物种类复杂,其安全问题关系国计民生。而基于预测微生物学的理论,将其应用于粮油食品构建真菌毒素污染预测模型,对粮油食品中真菌毒素污染的控制有重要意义和应用价值。文章对粮油食品中真菌毒素污染状况以及典型微生物预测模型进行了介绍,并分析了其在粮油食品供应链中的应用进展。对现阶段粮油食品毒素污染预测模型研究存在的问题及今后的发展进行了展望。     

浸泡、浸提对花生乳饮料中蛋白质溶出率的影响

着重分析了花生乳生产工艺中整粒花生浸泡条件、及磨浆后浸提条件对蛋白质溶出率的影响。根据正交试验分析确定:最佳工艺的浸泡条件是加水量为花生的12倍、浸泡液pH为7.5、浸泡温度为20℃、浸泡时间为14 h;最佳浸提条件是调花生浆的pH为7.5、70℃下浸提10min。花生蛋白的最高溶出率可达77%。     

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.     

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.     

A model for predicting salt equilibria in milk and mineral-enriched milks

The aim of this work was to present an original model predicting salt equilibria between the micellar and aqueous phases in milk and mineral-enriched milks. Calculations were based on interactions between cations (calcium, magnesium, sodium, potassium) and anions (citrate, chloride, inorganic phosphate and total caseins) according to their reciprocal affinity and considering pH, ionic strength, and solubility of calcium phosphate. In order to validate the model, the theoretical salt equilibria in milk and milks enriched with different salts (CaCl₂, NaCl, phosphate and citrate) at pH 6.75 were compared with experimental results published in the literature. Comparison of simulated results to known values reported in the literature showed a good agreement. In conclusion, this model constitutes an interesting tool for simulating salt equilibria in milk in order to prepare various dairy formulations with different concentrations of minerals and caseins.     

A model system for studying the effects of colloidal calcium phosphate concentration on the rheological properties of Cheddar cheese

A novel model system was developed for studying the effects of colloidal Ca phosphate (CCP) concentration on the rheological properties of Cheddar cheese, independent of proteolysis and any gross compositional variation. Cheddar cheese slices (disks; diameter = 50 mm, thickness = 2 mm) were incubated in synthetic Cheddar cheese aqueous phase solutions for 6 h at 22°C. Control (unincubated) Cheddar cheese had a total Ca and CCP concentration of 2.80 g/100 g of protein and 1.84 g of Ca/100 g of protein, respectively. Increasing the concentration of Ca in the synthetic Cheddar cheese aqueous phase solution incrementally in the range from 1.39 to 8.34 g/L significantly increased the total Ca and CCP concentration of the cheese samples from 2.21 to 4.59 g/100 g of protein and from 1.36 to 2.36 g of Ca/100 g of protein, respectively. Values of storage modulus (index of stiffness) at 70°C increased significantly with increasing concentrations of CCP, but the opposite trend was apparent at 20°C. The maximum in loss tangent (index of meltability/flowability) decreased significantly with increasing concentration of CCP, and there was no significant effect on the temperature at which the maximum in loss tangent occurred (68 to 70°C). Fourier transform mechanical spectroscopy showed the frequency dependence of all of the cheese samples increased with increasing temperature; however, solubilization of CCP increased the frequency dependence of the cheese matrix only in the high temperature region (i.e., >35°C). These results support earlier studies that hypothesized that the concentration of CCP strongly modulates the rheological properties of cheese.     

Kinetics of calcium phosphate nucleation and growth on calcite: implications for predicting the fate of dissolved phosphate species in alkaline soils

Unraveling the kinetics of calcium orthophosphate (Ca-P) precipitation and dissolution is important for our understanding of the transformation and mobility of dissolved phosphate species in soils. Here we use an in situ atomic force microscopy (AFM) coupled with a fluid reaction cell to study the interaction of phosphate-bearing solutions with calcite surfaces. We observe that the mineral surface-induced formation of Ca-P phases is initiated with the aggregation of clusters leading to the nucleation and subsequent growth of Ca-P phases on calcite, at various pH values and ionic strengths relevant to soil solution conditions. A significant decrease in the dissolved phosphate concentration occurs due to the promoted nucleation of Ca-P phases on calcite surfaces at elevated phosphate concentrations and more significantly at high salt concentrations. Also, kinetic data analyses show that low concentrations of citrate caused an increase in the nucleation rate of Ca-P phases. However, at higher concentrations of citrate, nucleation acceleration was reversed with much longer induction times to form Ca-P nuclei. These results demonstrate that the nucleation-modifying properties of small organic molecules may be scaled up to analyze Ca-P dissolution-precipitation processes that are mediated by a more complex soil environment. This in situ observation, albeit preliminary, may contribute to an improved understanding of the fate of dissolved phosphate species in diverse soil systems.     

冲泡过程对条斑紫菜多糖溶出的影响及其动力学研究

基于Fick第二定律,对颗粒状和片状条斑紫菜冲泡过程中多糖的溶出进行动力学分析。测定条斑紫菜冲泡液中多糖溶出随冲泡水温及时间的变化,建立颗粒状和片状条斑紫菜冲泡过程的多糖溶出动力学模型。结果表明在整个冲泡过程中,颗粒状紫菜中多糖溶出率均大于片状紫菜。对于颗粒状紫菜,冲泡水温的影响大于冲泡时间,以363.15 K(90℃)热水或373.15 K(100℃)沸水冲泡20 min,其多糖溶出率达到62.07%和64.05%。实验数据与动力学模型计算值吻合良好(R>0.933);紫菜多糖溶出表观速率常数和扩散系数均随冲泡温度的升高而增加;颗粒状和片状紫菜多糖溶出过程的活化能分别为5.984、1.406 k J/mol;多糖溶出相对萃余率符合指数模型。该动力学模型可为条班紫菜多糖最佳冲泡方式奠定理论基础。      

Chitosan phosphate: A new way for production of eco-friendly flame-retardant cotton textiles

An increase in the health and environment legislation awareness pushed the textile manufacturers to develop their strategies to produce eco-friendly flame-retardant textiles with competitive cost. Chitosan is added during the phosphorylation process as a nitrogen source that has synergistic effect with phosphorus. Increasing the chitosan concentration from 0% to 2% enhances the flame retardancy of the treated cotton fabric against successive washing. Further increase in amount of chitosan, above 2%, has a limited effect on the thermal degradation of the treated cotton. Increasing diammonium hydrogen phosphate (DAHP) concentration from 0% to 10% is responsible for making the flame-retardant finish durable against successive washing. Thermal degradation analysis of treated fabrics at different DAHP concentrations shows a decrease in the maximum degradation rate point and thermal degradation onset point. The amount of residue at 500°C increases till reaches 32% with the increase in the DAHP concentration. The effect of curing temperature and time has been discussed in detail. The performance properties of the treated cotton fabrics show better physical and chemical properties than that in the absence of chitosan.     

Dynamic predictive model for the growth of Salmonella spp. in liquid whole egg

Abstract: A dynamic model for the growth of Salmonella spp. in liquid whole egg (LWE) (approximately pH 7.8) under continuously varying temperature was developed. The model was validated using 2 (5 to 15 °C; 600 h and 10 to 40 °C; 52 h) sinusoidal, continuously varying temperature profiles. LWE adjusted to pH 7.8 was inoculated with approximately 2.5–3.0 log CFU/mL of Salmonella spp., and the growth data at several isothermal conditions (5, 7, 10, 15, 20, 25, 30, 35, 37, 39, 41, 43, 45, and 47 °C) was collected. A primary model (Baranyi model) was fitted for each temperature growth data and corresponding maximum growth rates were estimated. Pseudo‐R² values were greater than 0.97 for primary models. Modified Ratkowsky model was used to fit the secondary model. The pseudo‐R² and root mean square error were 0.99 and 0.06 log CFU/mL, respectively, for the secondary model. A dynamic model for the prediction of Salmonella spp. growth under varying temperature conditions was developed using 4th‐order Runge–Kutta method. The developed dynamic model was validated for 2 sinusoidal temperature profiles, 5 to 15 °C (for 600 h) and 10 to 40 °C (for 52 h) with corresponding root mean squared error values of 0.28 and 0.23 log CFU/mL, respectively, between predicted and observed Salmonella spp. populations. The developed dynamic model can be used to predict the growth of Salmonella spp. in LWE under varying temperature conditions. Practical Application: Liquid egg and egg products are widely used in food processing and in restaurant operations. These products can be contaminated with Salmonella spp. during breaking and other unit operations during processing. The raw, liquid egg products are stored under refrigeration prior to pasteurization. However, process deviations can occur such as refrigeration failure, leading to temperature fluctuations above the required temperatures as specified in the critical limits within hazard analysis and critical control point plans for the operations. The processors are required to evaluate the potential growth of Salmonella spp. in such products before the product can be used, or further processed. Dynamic predictive models are excellent tools for regulators as well as the processing plant personnel to evaluate the microbiological safety of the product under such conditions.     

A new method for predicting sorption isotherms at different temperatures using the BET model

A new methodology to predict sorption isotherms at different temperatures is proposed in this work. The classical BET model is used coupled with the Clausius–Clapeyron equation, and an Arrhenius temperature dependency is assumed for the BET energetic parameter C. When compared to the usual procedure based solely on the use of a model for the sorption isotherm, this methodology presents two main advantages: (i) a single set of parameters may be used to predict isotherms at different temperatures and (ii) fewer experimental data are required to estimate this set of parameters, using only one single sorption isotherm and one single value of differential enthalpy of sorption, at a specific and arbitrary humidity. The new methodology was tested with different food materials and the predicted results were in good agreement with experimental data, attesting the potential of this new approach.     

冷冻鱼糜中金黄色葡萄球菌生长预测模型的筛选

为建立冷冻鱼糜中金黄色葡萄球菌生长预测模型,将金黄色葡萄球菌接种到冷冻鱼糜制品中,分别采用Gompertz模型、Logistic模型、Richards模型,拟合金黄色葡萄球菌在10,15,20,25℃条件下的生长数据,通过残差分布以及拟合度(RSS、RSE、AIC)等统计指标,分析比较4种模型的拟合能力,建立各温度条件下金黄色葡萄球菌最适一级生长模型。结果表明:10℃条件下Logistic模型拟合的RSS、RSE、AIC值最小,分别是0.742,0.352,-4.458;而Gompertz模型在15,20,25℃条件下拟合的RSS、RSE、AIC值最小,分别是0.403,0.259,-9.961;0.285,0.239,-13.089和0.273,0.234,-13.473。综合比较,10℃条件下,冷冻鱼糜中金黄色葡萄球菌最适一级生长模型为Logistic模型,而15,20,25℃适合采用Gompertz模型。     

Ultrasound-assisted chemical dissolution for quantitative analysis of wool in textile blends

The objective is to explore the feasibility of ultrasound technology for quantitative analysis of wool in blended fabrics with chemical dissolution. Two varieties of mixture fabric with wool content of 45.1 and 16.7% were employed and were dissolved in solution of sodium hypochlorite with ultrasound assistance at different frequencies of 20, 28 and 40 kHz. By statistical method, the data for both blends indicated that there were no significant difference among the three ultrasound frequencies when applied to textile quantitative chemical analysis. For evaluation of ultrasound reliability, two insoluble materials were dissolved in sodium hypochlorite. Relative errors showed that ultrasound has little impact on the quality of insoluble fibers as well as mechanical stirring. Compared with mechanical agitation, wool was dissolved completely in a short time and at low liquor ratio when assisted with ultrasound. The results suggested that it was feasible to quantitatively analyze the wool in blended fabrics with chemical dissolution by ultrasound technology.     

Experimental evidence for previously unclassified calcium phosphate structures in the casein micelle

¹H-³¹P Cross-polarization magic angle spinning (CP-MAS) measurements of 40-d-old Mozzarella cheese and 20 mM EDTA-treated casein micelles revealed that each sample had immobile phosphorus with the same spectral pattern, which did not match that of native casein micelles. To identify the immobile phosphorus bodies, ¹H-³¹P CP-MAS spectra and cross-polarization kinetics measurements were undertaken on native casein micelles, EDTA-chelated casein micelles, and reference samples of β-casein and hydroxyapatite. The results showed that the immobile phosphorus bodies in the mature Mozzarella cheese had the following characteristics: they are immobile phosphoserine residues (not colloidal calcium phosphate); they are not the product of phosphoserine to colloidal calcium phosphate bridging; the phosphate is complexed to calcium; their rigidity is localized to a phosphorus site; their rigidity and bond coupling is unaffected by protein hydration; and the immobile bodies share a narrow range of bond orientations. Combining these observations, the best explanation of the immobile phosphorus bodies is that bonding structures of phosphorus-containing groups and calcium exist within the casein micelle that are not yet clearly classified in the literature. The best candidate is a calcium-bridged phosphoserine-to-phosphoserine linkage, either intra- or inter-protein.     

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.     

Flavonoid microparticles by spray-drying: Influence of enhancers of the dissolution rate on properties and stability

Naringenin (Nn) and Quercetin (Q) have numerous health benefits particularly due to their antioxidant properties. However, their low solubility, bioavailability and stability limit their use as components for functional foods, nutraceuticals and pharmaceutical agents. In this research, Nn- and Q-microparticles were produced by a spray-drying process using a combination of cellulose acetate phthalate (CAP) as coating gastroresistant polymer and swelling or surfactant agents as enhancers of dissolution rate. Raw materials and microparticles produced were all characterized by particle size analysis, differential scanning calorimetry, X-ray diffraction, and imaged by electron and fluorescence microscopy. During 12 months, storage stability was evaluated by analyzing drug content, HPLC and DSC profiles, as well as antioxidant activity (DPPH test). In vitro dissolution tests, using a pH-change method, were carried out to investigate the influence of formulative parameters on flavonoid release from the microparticles. Presence of a combination of CAP and surfactants or swelling agents in the formulations produced microparticles with good resistance at low pH of the gastric fluid and complete flavonoid release in the intestinal environment. The spray-drying technique and the process conditions selected have given satisfying encapsulation efficiency and product yield. The microencapsulation have improved the technological characteristics of the powders such as morphology and size, have given long-lasting storage stability and have preserved the antioxidant properties.     

A simple steady-state model for carry-over of aflatoxins from feed to cow's milk

A simple steady-state model is derived from two kinetic one-compartment models for the disposition of aflatoxin B₁ (AFB₁₎ and aflatoxin M₁ (AFM₁) in the lactating cow. The model relates daily intake of AFB₁ in feed of dairy cattle and the cow's lactation status to resulting concentrations of AFM₁ in milk. Moreover, assuming a linear relationship between the cow's lactation status and feed intake, the model relates daily milk production and AFB₁ concentration in total feed to AFM₁ levels in milk. The model explains similar experimental outcomes from different investigations into carry-over of aflatoxins from feed to milk. Although it is difficult to set a permanent limit for AFB₁ in feed, the European Union (EU) limit of 5 µg AFB₁ kg^-1 concentrate has proved, thus far, to be an appropriate level in preventing the EU limit of 0.05 µg AFM₁ kg^-1 milk being exceeded.