首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 0 毫秒
1.
Calcium lactate (CaL2) crystal formation on the surface of cheese continues to be a widespread problem for the cheese industry despite decades of research. To prevent those crystals from forming, it is necessary to keep the concentration of CaL2 below saturation level. The limited data available on the solubility of CaL2 at conditions appropriate for the storage of cheese are often conflicting. In this work, the solubility of L(+)-CaL2 in water was evaluated at 4, 10, and 24 degrees C, and the effects of salt and pH at those temperatures were investigated. The effects of additional calcium and lactate ions on solubility also were studied. The results suggested that temperature and the concentration of lactate ions are the main factors influencing the solubility of CaL2, with the other parameters having limited effect.  相似文献   

2.
3.
Polyphosphate blends are used in food such as meat and dairy products to improve their texture and stability by sequestering metal ions. This study aims to analyse the impact of high temperature treatments on the composition of polyphosphates with regards to phosphate chain length in aqueous solutions with or without calcium. Temperature treatments of 120 °C for 10 min led to the hydrolytic degradation of long-chain phosphates into orthophosphate and trimetaphosphate whereas heating the salts to 100 °C in aqueous solutions had little effect on their composition. The presence of calcium increased the hydrolysis rate of long-chain phosphates and led to more trimetaphosphate and pyrophosphate as end products. The evolution of emulsifying salts’ composition under heat treatment may lead to a modification of their chelating properties since short-chain phosphates are less efficient to chelate calcium than long-chain phosphates.  相似文献   

4.
Binary mutual diffusion coefficients (interdiffusion coefficients) of calcium gluconate (C12H22CaO14) in water at 298.15 K and at concentrations between 0.001 and 0.0500 mol dm−3 have been measured, using a Taylor dispersion method. These data are discussed on the basis of the Onsager-Fuoss model. Based on these data, the equivalent conductance at infinitesimal concentration of the gluconate ion in the studied solutions has been estimated. Through the same technique, ternary mutual diffusion coefficients (D11, D22, D12 and D21) for aqueous solutions containing calcium gluconate and lactose, at = 298.15 K, and at different carrier concentrations, were also measured. These data permit us to have a better understanding of the structure of these systems and the thermodynamic behaviour of calcium gluconate in different media.  相似文献   

5.
The interaction between resveratrol (Res) and sodium caseinate (Na-Cas) has been studied by measuring fluorescence quenching of the protein by resveratrol. Quenching constants were determined using Stern–Volmer equation, which suggests that both dynamic and static quenching occur between Na-Cas and Res. Binding constants for the complexation between Na-Cas and Res were determined at different temperatures. The large binding constants (3.7–5.1 × 105 M−1) suggest that Res has strong affinity for Na-Cas. This affinity decreases as the temperature is raised from 25 to 37 °C. The binding involves both hydrogen bonding and hydrophobic interaction, as suggested by negative enthalpy change and positive entropy change for the binding reaction. The present study indicates that Na-Cas, a common food protein, may be used as a carrier of Res, a bioactive polyphenol which is insoluble in both water and oils.  相似文献   

6.
7.
The objectives of this study are to investigate the kinetics of bromamine decomposition and to identify the corresponding relevant reactions. Experiments were performed with a stopped-flow spectrophotometer system. Experimental variables investigated included pH (6.5-9.5), bromamines concentration (0.15-0.50 mM), ammonia to bromine ratio (5-100), and phosphate and carbonate buffers concentration (5-40 mM). The experimental results were consistent with a reaction scheme that involved the reversible disproportionation of monobromamine into dibromamine and ammonia (2NH2Br (k1)<=>(k(-1)) NHBr2 + NH3), followed by irreversible decomposition of monobromamine and dibromamine into products (2NHBr2 (k2) --> products and NH2Br + NHBr2 (k3) --> products). The monobromamine disproportionation reaction was found to undergo general acid catalysis, and the two subsequent decomposition reactions were found to experience base catalysis. Experimental results were analyzed for the determination of catalysis terms corresponding to H+, NH4+, H2PO4-, HCO3-, and H2O for rate constants k1 and k(-1); HPO4(2-) and H2O for k2; and OH-, CO3(2-), and H2O for k3. These constants were fitted with the Br?nsted relationship, and the resulting fitting expressions were used to calculate any relevant catalysis rate constants that could not be determined at the range of experimental conditions used.  相似文献   

8.
In this paper, a new technique has been developed to enable fibre diameters to be measured in an aqueous environment using the OFDA 2000 instrument. The existing OFDA instrument has only been used to measure diameters of animal fibres under dry conditions. This new technique was utilised to assess the effects of pH and temperature on the diameters of merino wool fibres in aqueous environments. Significant changes in fibre diameter under aqueous conditions were found as a function of pH and temperature. Wool fibre diameters were at a minimum close to the wool isoelectric point (pH 4.8) and increased at both lower and higher pHs. Swelling of merino wool fibres was observed to increase linearly by around 15% as the temperature rose from ambient to 70°C.  相似文献   

9.
张宾  董霞  何瑾馨 《印染》2012,38(14):1-5
采用表面张力法、荧光光谱法和动态光散射法研究了染料聚醚衍生物在水溶液中的性质,包括表面活性、微极性、临界胶束浓度、单个吸附分子所占面积和胶束动力学直径等,推测了其形成胶束结构形态,并与相应聚醚进行对比.结果表明,染料聚醚衍生物的表面活性比聚醚更高,在质量浓度大于0.5 g/L的水溶液中可形成稳定的动力学直径在50~ 150 nm的胶束,其胶束结构疏松,内部被水分子高度溶胀.  相似文献   

10.
铅作为对人体有害的重金属元素之一,是食品及食品添加剂中重要的检测项目。本实验主要研究氢化物原子吸收光谱法(HG-AAS)测定碳酸钙中铅含量的分析方法。在适当的实验条件下,方法线性范围为0 10μg/L,相关系数r=0.9998,检出限为0.08363μg/L,回收率为96.8%100.5%,结果表明用该方法测定碳酸钙中铅含量灵敏度高,回收率较好,操作简单,是定量测定碳酸钙中铅含量的可靠方法之一。  相似文献   

11.
The objective of this research is to evaluate the thermal stability of monoammonium glycyrrhizinate. Thermodegradation of solutions of monoammonium glycyrrhizinate at various temperatures (50, 70 and 90°C) was studied. This degradation appeared to follow first-order kinetics independently of temperature and was found to be pH dependent. The experiments revealed an activation energy (Ea) of about 33 kJ mol−1 and a t90% of about 3 years at 20°C in a pH range from 7 to 9. So it can be concluded that monoammonium glycyrrhizinate is stable in a pH range from 7 to 9. It can be interesting for use in oral care or in food industry. © 1998 SCI.  相似文献   

12.
Several taste substances were tested in aqueous solutions; tannic and tartaric acids were found unsuitable as a standard substance for the taste identification. Monosodium glutamate, sodium hydrogen carbonate and potassium chloride were often identified as salty substances even when the subjects were able to distinguish between the tastes. They probably identified the taste as salty owing to the lack of proper terms, and unsufficient experience with tasting monosodium glutamate and sodium hydrogen carbonate as substances possessing defined tastes different from the salty taste.  相似文献   

13.
14.
A systematic survey was made of water activity reduction in single non electrolyte aqueous solutions together with an examination of the theoretical aspects of a W predictions. The prediction of a W in multicomponent aqueous solutions of non electrolytes as well as of mixed strong electrolyte–non electrolyte solutions was also studied.  相似文献   

15.
Gelation and microstructure of dilute gellan solutions with calcium ions   总被引:1,自引:0,他引:1  
The viscoelasticity at 25 °C and microstructure of 0.02–0.07 wt% of low acyl gellan aqueous media were investigated for ratios of Ca2+ to gellan in the range of 0–38.8, using small amplitude oscillatory shear rheometry and confocal laser scanning microscopy (CLSM), respectively. The total ionic concentration (CT = γ CP + CS, being CP and CS the gellan and calcium concentrations, respectively, and γ the mean activity coefficient) of the systems was found to be the triggering and critical factor for the gelation and elasticity of gellan systems. The gel point (Tgel) and storage moduli (G′) increased upon increasing CT. However, G′ showed a maximum for CT = 9.3 ± 1.2 meq/L, followed by a progressive reduction as CT increased; this was primarily due to further addition of calcium, as CP had a low contribution to CT of the systems. CLSM demonstrated that the level of counter-ions was enough to induce the formation of a network, whose connection depended on CP and whose reinforcement was ion dependent. Therefore, even at very low levels of gellan, it is possible to create a wide spectrum of viscoelastic behaviors going from structured liquids to strong gels through the specific combinations of gellan and cation concentrations.  相似文献   

16.
The combination of copper and N-methylol compounds considerably improves the performance against copper sensitive fungi (G. trabeum and T. versicolor), while the fungicidal effect against copper tolerant strain (A. vaillantii) remained insufficient. Addition of N-methylol compounds to copper solution significantly reduces leaching from wood blocks impregnated with the solution of the lowest copper concentration (cCu =0.1%), and less notably reduces leaching from wood blocks impregnated with solutions of higher copper contents (cCu=0.5%).  相似文献   

17.
The combination of copper and N-methylol compounds considerably improves the performance against copper sensitive fungi (G. trabeum and T. versicolor), while the fungicidal effect against copper tolerant strain (A. vaillantii) remained insufficient. Addition of N-methylol compounds to copper solution significantly reduces leaching from wood blocks impregnated with the solution of the lowest copper concentration (cCu =0.1%), and less notably reduces leaching from wood blocks impregnated with solutions of higher copper contents (cCu=0.5%).  相似文献   

18.
Gum ghatti contains a soluble gum and an insoluble gel which partially dissolves on boiling. Maceration of the gel in water gives a perfectly stable dispersion which for practical purposes behaves as a solution. The viscosity of the gel dispersion is ca 10–30 times that of the soluble gum. The proportion of gel in four commercial batches of gum ghatti varied from 8 to 23 %. The viscosity of the whole gum dispersion depends largely on the proportion of gel. The viscosity of gum ghatti can be closely controlled by blending to a fixed proportion of gel.  相似文献   

19.
Tamarind seed gum as seed polysaccharide from Tamarindus indica L. has been characterized for physicochemical and rheological properties in the present work. The structural analysis determined the presence of glucose:xylose:galactose in a molar ratio of 2.61:1.43:1.The Huggins and Kraemer plots obtained by capillary viscometry gave an intrinsic viscosity of 4.7 dl g−1 and the viscosity average molecular mass was calculated to be 9.18 × 105 g mol−1 using the Mark-Houwink relationship. The steady shear and dynamic viscoelasticity properties of tamarind seed gum in aqueous solutions at different concentrations were investigated at 20 °C using a Haake Rheometer RS75. The tamarind seed gum solutions clearly exhibited shear-thinning flow behaviour at high shear rate and Newtonian region occurred at low shear rate range, however, at higher concentrations, pronounced shear thinning was observed. The value of zero shear viscosity (η0) was estimated by fitting Cross and Carreau models. The specific viscosity at zero shear rate (ηsp0) was plotted against the coil overlap parameter (C[η]) and the slopes of the lines in the dilute and semi-dilute regions were found to be ∼2.2 and 4.3, respectively. The value of the critical concentration (C) was about 4.23/[η]. While, the mechanical spectra in the linear viscoelastic region of tamarind seed gum solutions showed the typical shape for macromolecular solutions. Plots of η versus γ and η versus ω were superimposable and hence obey the Cox-Merz rule.  相似文献   

20.
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号