Thermal Decomposition of Some Chemical Compounds Used As Food Preservatives and Kinetic Parameters of This Process

Thermal decomposition processes of selected chemicals used as food preservatives such as sodium formate, sodium propionate, sodium nitrates(V and III) and sodium sulphate(IV) were examined by the derivatographic method. Based on the curves obtained, the number of decomposition stages and characteristic temperatures of these compounds have been found. Mass decrements calculated from TG curves ranged from 28.9% for sodium formate to 77.8% for sodium nitrate(V), while sodium sulphate showed a mass increment of 5.6%. Kinetic parameters such as activation energy (E _a ), frequency factor (A ) and reaction order (n ) were calculated from TG, DTG and T curves. Sodium formate shows the highest values of E _a and A which amount to 171.7 kJ mol^–1 and 5.8⋅10¹⁴ s^–1 , respectively, while the lowest ones, E _a =28.2 kJ mol^–1 and A =3.65⋅10² s^–1 belong to sodium nitrate(V). This revised version was published online in August 2006 with corrections to the Cover Date.     

Antimicrobial Properties of Lyophilized Extracts of Olive Fruit,Pomegranate and Orange Peel Extracts against Foodborne Pathogenic and Spoilage Bacteria and Fungi In Vitro and in Food Matrices

Several novel antimicrobials with different concentrations of olive, pomegranate, and orange fruit pulp extracts were produced from agricultural byproducts and, after lyophilization, their antimicrobial activity and potential synergistic effects were evaluated in vitro and in food samples against foodborne pathogenic and spoilage bacteria and fungi. The Minimum Inhibitory of the tested bacteria was 7.5% or 10%, while fungi were inhibited at a concentration of 10% or above. The optical density of bacterial and yeast cultures was reduced to a different extent with all tested antimicrobial powders, compared to a control without antimicrobials, and mycelium growth of fungi was also restricted with extracts containing at least 90% olive extract. In food samples with inoculated pathogens and spoilage bacteria and fungi, the 100% olive extract was most inhibitory against E. coli, S. typhimurium, and L. monocytogenes in fresh burger and cheese spread samples (by 0.6 to 1.8 log cfu/g), except that S. typhimurium was better inhibited by a 90% olive and 10% pomegranate extract in burgers. The latter extract was also the most effective in controlling the growth of inoculated fungi (Aspergillus niger, Penicillium italicum, Rhodotorula mucilaginosa) in both yogurt and tomato juice samples, where it reduced fungal growth by 1–2.2 log cfu/g at the end of storage period. The results demonstrate that these novel encapsulated extracts could serve as natural antimicrobials of wide spectrum, in order to replace synthetic preservatives in foods and cosmetics.     

藏红T共振瑞利散射光谱法测定保健食品中的透明质酸钠

建立藏红T共振瑞利散射光谱法测定保健食品中透明质酸钠的含量。在p H 5.00的Britton–Robinson缓冲介质中,藏红T与透明质酸钠反应形成化合物,使溶液共振瑞利散射急剧增强并产生相应的散射光谱,其最大散射峰位于335 nm,5.0×10~(–4) mol/L藏红T溶液用量为0.70 m L,反应时间为15 min。透明质酸钠的质量浓度在0.06~3.0mg/L范围内与共振瑞利散射增强程度成良好的线性关系,线性相关系数为0.999 2。方法检出限为19.8μg/L,测定结果的相对标准偏差为3.36%~4.52%(n=6),加标回收率为92.4%~103.0%。该方法灵敏度高、选择性好、操作简便,适用于保健食品中透明质酸钠的测定。     

高效液相色谱法同时测定食品中丙酸钙(钠)和双乙酸钠

建立高效液相色谱法同时测定食品中的丙酸钙(钠)和双乙酸钠。采用Acclaim120 C_(18)色谱柱(150mm×4.6 mm,5μm),以1.5 g/L磷酸氢二铵溶液(用1 mol/L磷酸溶液调pH至2.7~3.5)–甲醇混合液(体积比为95∶5)作为流动相,流量为1.0 mL/min,在214 nm波长下检测。丙酸与双乙酸钠的质量浓度在0.05~0.5 mg/mL范围内线性关系良好,相关系数均大于0.999。丙酸和双乙酸钠的加标回收率分别为95.58%~98.95%,96.12%~99.25%,测定结果的相对标准偏差分别为1.50%,1.41%(n=6)。该法适用于糕点及调味品中丙酸钙(钠)和双乙酸钠含量的检测。     

综合设计性实验:食品添加剂甘氨酸钠碳酸盐的合成及性质初探

介绍一个综合设计性实验——食品添加剂甘氨酸钠碳酸盐的合成及性质初探。学生查阅文献,设计实验方案,采用湿法、超声法、微波法合成甘氨酸钠碳酸盐并对合成方法进行比较,学习使用红外和紫外大型分析仪器对产物进行表征,并对产物的性质进行了初步探讨,最后总结实验结果,进行答辩,完整地进行了一次简单的科研实践过程。     

反相离子对高效液相色谱法快速分离和定量测定食品中的甜蜜素

采用反相离子对高效液相色谱法快速分离和测定食品中的甜蜜素。在ODS柱上,以V（甲醇）：V（水,含离子对试剂）=30：70的溶液为流动相进行分离,分别考察了流动相中离子对试剂和甲醇浓度对甜蜜素保留行为的影响。检测波长为205nm;采用外标法定量,测得甜蜜素在0．5～2．5g／L范围内具有良好的线性关系;回收率在96．9％～101．7％之间;检测限为0．05g／L。     

Facile Stabilization of the Sodium Metal Anode with Additives: Unexpected Key Role of Sodium Polysulfide and Adverse Effect of Sodium Nitrate

Sodium metal is an attractive anode for next‐generation energy storage systems owing to its high specific capacity, low cost, and high abundance. Nevertheless, uncontrolled Na dendrite growth caused by the formation of unstable solid electrolyte interphase (SEI) leads to poor cycling performance and severe safety concerns. Sodium polysulfide (Na₂S₆) alone is revealed to serve as a positive additive or pre‐passivation agent in ether electrolyte to improve the long‐term stability and reversibility of the Na anode, while Na₂S₆‐NaNO₃ as co‐additive has an adverse effect, contrary to the prior findings in the lithium anode system. A superior cycling behavior of Na anode is first demonstrated at a current density up to 10 mA cm^?2 and a capacity up to 5 mAh cm^?2 over 100 cycles. As a proof of concept, a high‐capacity Na‐S battery was prepared by pre‐passivating the Na anode with Na₂S₆. This study gives insights into understanding the differences between Li and Na systems.     

藏红T与六偏磷酸钠的相互作用及在食品分析中的应用

对阳离子荧光染料藏红T（ST）在食品添加剂六偏磷酸钠（SHMP）存在时的溶液状态的荧光光谱及吸收光谱进行了研究。 结果发现,在醋酸-醋酸钠缓冲条件下,SHMP使ST溶液发生自聚集,同时因静电作用二者形成杂化聚集体,导致ST的荧光强度和吸光度降低且在476 nm处出现新的吸收峰,但ST的荧光寿命没有发生明显的变化,表明SHMP静态猝灭ST的荧光。 根据SHMP存在时ST吸光度的变化,建立了一种检测食品添加剂六偏磷酸钠的新方法,线性范围为1.0×10-6~1.1×10-5 mol/L,检测限为3.4×10-7 mol/L。 方法成功应用于饮料中六偏磷酸钠的测定,相对标准偏差小于4.6%,回收率在95.0%~104.0%之间。     

焙烤食品中糖精钠、富马酸二甲酯、苯甲酸和山梨酸的高效液相色谱法测定

研究了采用高效液相色谱同时测定焙烤食品中糖精钠、富马酸二甲酯、苯甲酸和山梨酸的检测方法；样品经氨化甲醇溶液提取后，用盐酸中和，水定容过滤后即可直接测定；检测波长220m，流动相采用甲醇与含0．03mol/L乙酸钠-0．03mol/L冰醋酸—0．008mol/L溴化四丁铵的水溶液混合液(体积比35：65)；4种组分的回收率在85％—109％之间，相对标准偏差小于6．2％(n=6)；该法简单、快速、准确，可用于饼干、月饼等焙烤食品中糖精钠、富马酸二甲酯、苯甲酸和山梨酸的日常检测。     

Synthesis of Some Novel 1,2-Disubstituted Benzimidazole-5-carboxylates via One-Pot Method Using Sodium Dithionite and Its Effect on N-Debenzylation

A series a novel of 1,2-disubstituted benzimidazole-5-carboxylates were prepared by the one-pot nitroreductive cyclization route using sodium dithionite, and its effect on N-debenzylation has been described. Different ethyl 4-(alkyl/arylamino)-3-nitrobenzoates were reacted with various aromatic/heteroaromatic aldehydes in dimethyl sulfoxide to yield the target benzimidazoles in good yield and purity. Wide varieties of aldehydes used for the cyclization were found to be susceptible under the reaction conditions. This method afforded the products within a very short reaction time and isolation was an easy workup procedure. Debenzylation resulting in the cleavage of the N-benzyl group was observed under experimental conditions with sodium dithionite without the aid of any cocatalyst and the presence of ethanol increased the extent of debenzylation.     

A Novel Catalytic Method for the Oxidation of Sulfides to Sulfoxides with Silica Sulfuric Acid and Sodium Nitrite in the Presence of KBr and/or NaBr as Catalyst

Highly efficient selective oxidation of sulfides to sulfoxides by NaNO₂ and silica sulfuric acid catalyzed with KBr or NaBr has been reported. This oxidation was carried out in the presence of wet SiO₂ (50% w/w) in acetonitrile at room temperature with good to excellent yields.     

Improvement of Naturally Derived Food Colorant Performance with Efficient Pyranoanthocyanin Formation from Sambucus nigra Anthocyanins Using Caffeic Acid and Heat

Consumers and regulations encourage the use of naturally derived food colorants. Anthocyanins (ACN), plant pigments, are unstable in foods. In aged red wines, ACN with a free hydroxyl group at C-5 condenses to form pyranoanthocyanins (PACN), which are more stable but form inefficiently. This study attempted to produce PACN efficiently using high cofactor concentration and heat. Elderberry anthocyanins were semi-purified and caffeic acid (CA) was dissolved in 15% ethanol and diluted with a buffer to achieve ACN:CA molar ratios of 1:50, 1:100, 1:150, and 1:200, then incubated at 65 °C for 5 days. The effect of temperature was tested using ACN samples incubated with or without CA at 25 °C, 50 °C, and 75 °C for 7 days. Compositional changes were monitored using uHPLC-PDA-MS/MS. Higher CA levels seemed to protect pigment integrity, with ACN:CA 1:150 ratio showing the highest tinctorial strength after 48 h. PACN content growth was fastest between 24 and 48 h for all ACN:CA ratios and after 120 h, all ACN had degraded or converted to PACN. PACN formed faster at higher temperatures, reaching ~90% PACN in 24 h and ~100% PACN in 48 h at 75 °C. These results suggest that PACN can form efficiently from elderberry ACN and CA if heated to produce more stable pigments.     

Synergistic Effect of Propidium Iodide and Small Molecule Antibiotics with the Antimicrobial Peptide Dendrimer G3KL against Gram-Negative Bacteria

There is an urgent need to develop new antibiotics against multidrug-resistant bacteria. Many antimicrobial peptides (AMPs) are active against such bacteria and often act by destabilizing membranes, a mechanism that can also be used to permeabilize bacteria to other antibiotics, resulting in synergistic effects. We recently showed that G3KL, an AMP with a multibranched dendritic topology of the peptide chain, permeabilizes the inner and outer membranes of Gram-negative bacteria including multidrug-resistant strains, leading to efficient bacterial killing. Here, we show that permeabilization of the outer and inner membranes of Pseudomonas aeruginosa by G3KL, initially detected using the DNA-binding fluorogenic dye propidium iodide (PI), also leads to a synergistic effect between G3KL and PI in this bacterium. We also identify a synergistic effect between G3KL and six different antibiotics against the Gram-negative Klebsiella pneumoniae, against which G3KL is inactive.     

Effect of p-tert-Butylcalix[4]arene Fitted with Phosphinoyl Pendant Arms as Synergistic Agent in the Solvent Extraction and Separation of Some Trivalent Lanthanoids with 4-Benzoyl-3-methyl-1-phenyl-5-pyrazolone

The synergistic solvent extraction of five selected lanthanoid ions (La³⁺, Nd³⁺, Eu³⁺, Ho³⁺ and Lu³⁺) with a 4-benzoyl-3-methyl-1-phenyl-5-pyrazolone(HP) and the 5,11,17,23-tert-butyl-25,26,27,28-tetrakis(dimethylphosphinoylmethoxy)calix[4]arene, (S) in CHCl₃ has been studied. It was found that in presence of this phosphorus-containing calix[4]arene the lanthanoids have been extracted as LnP₃ · S. On the basis of the experimental data, the values of the equilibrium constants have been calculated. The influence of the synergistic agent on the extraction process has been discussed. A synergistic effect of almost three orders of magnitude occurs in the extraction of Ln(III) with mixture of HP and S. The values of the separation factors (S.F.) between the adjacent elements have been evaluated. On the basis of the IR and NMR spectra the stoichiometry and the structure of the solid complexes of Eu(III) with HP and Eu(III) with HP and S were proposed.