果胶酶对柑橘汁的澄清效果研究

直接用果胶酶对柑橘汁的澄清进行了单因素实验及正交实验.单因素实验结果表明,果胶酶用量为0.08～0.10 g·L-1、温度为30～40℃、pH值为3.0～4.5条件下,果胶酶对柑橘汁澄清处理的效果较好.正交实验确定果胶酶对柑橘汁澄清的最佳工艺条件是:果胶酶用量0.10 g·L-1、温度40℃、pH值4.0.     

果胶酶降解柑桔罐头生产废水中果胶的研究

针对目前柑桔罐头生产废水难处理的现状,研究利用果胶酶来降解废水中的果胶,使废水易于后续生化处理.选择温度、pH、酶用量、反应时间四因素三水平进行正交试验,探索果胶酶处理优化工艺条件.实验表明,优化工艺条件为pH 4.5,果胶酶用量(以单位废水计)0.4 g/L,反应温度35℃,反应时间1.0 h,在此条件下果胶酶能较好地去除废水中的果胶.     

Understanding the role of d-Allulose and soy protein addition in pectin gels

d -Allulose (a monosaccharide and C3 epimer of fructose), one of the common rare sugars is getting attention due to its low caloric values. In this study, d -Allulose was used as a replacement of sucrose at different ratios (d -Allulose/Sucrose: 35/0, 20/15, 10/25, 0/35) to formulate pectin-based soft confectionery gels. Soy protein isolate was also added to increase the protein content. Physical properties, such as hardness, moisture content, pH, and color, were measured for the gels. Higher hardness values were obtained for the soy protein containing gels due to pectin–soy protein interaction (p < 0.05). Also, higher moisture content was observed in soy protein containing gels (p < 0.05). In addition, nuclear magnetic resonance T₂ relaxation times were measured at low field (~0.5 T) to determine how the water distribution in the samples changed and to observe how d -Allulose affected the polymer–water interactions. The study also showed that the presence of d -Allulose increased the crystallization tendency (% crystallinity of 7.9) of the pectin gels. X-ray diffraction results showed the d -allulose peaks at 33.76 and 48.68^oθ. Morphologies of the gels were also examined by scanning electron microscope. Sugar type and soy protein isolate addition were found to have significant impact on the gel formulations.     

Modelling of the inactivation kinetics of Escherichia coli,Saccharomyces cerevisiae and pectin methylesterase in orange juice treated with ultrasonic-assisted supercritical carbon dioxide

The combined effect of supercritical carbon dioxide (SC-CO₂) and high power ultrasound (HPU) on the inactivation kinetics of Escherichia coli, Saccharomyces cerevisiae and pectin-methyl esterase (PME) in orange juice was studied in order to select models that can predict their inactivation behaviour based on process parameters. Experiments were performed at different temperatures (31–41 °C, 225 bar) and pressures (100–350 bar, 36 °C). The inactivation rate of E. coli, S. cerevisiae and PME increased with pressure and temperature during SC-CO₂ + HPU treatments. The SC-CO₂ + HPU inactivation kinetics of E. coli, S. cerevisiae and PME were represented by models that included temperature, pressure and treatment time as variables, based on the Biphasic, the Peleg Type B, and the fractional models, respectively. The HPU-assisted SC-CO₂ batch system permits the use of mild process conditions and treatment times that can be even shorter than those of continuous SC-CO₂ systems.     

戈尔膜过滤新工艺与道尔澄清盐水精制工艺、技术及经济的比较

我公司隔膜碱生产能为为6万t/a的老企业，原工艺流程叙述。     

Distinct roles of conventional non-covalent and cation-π interactions in protein stability

The different roles played by conventional non-covalent and cation-π interactions in stabilizing protein structures have been investigated using a dataset of 62 non-redundant DNA binding proteins. The stabilizing residues have been identified by a consensus approach using the concepts of hydrophobicity, long-range interactions and conservation of amino acid residues. The cation-π interactions have been delineated based on a geometric approach, such as, distance and energy criteria. I have identified 138 and 196 stabilizing residues, based on non-covalent and cation-π interactions, respectively. Interestingly, the stabilizing residues identified by consensus approach are not contributing to cation-π interactions. Further, 99% of the cation-π interactions forming residues are not identified as stabilizing ones. These results demonstrate that the roles of cation-π and non-covalent interactions are different from each other to the stability of protein structures. I have further evaluated the range of surrounding hydrophobicity, long-range order, stabilization center and conservation score for the residues that are contributing to cation-π interactions. The average surrounding hydrophobicity and long-range order of cation-π interaction forming residues are in the range of 7-15 kcal/mol and 0-0.03, respectively. I suggest that the inclusion of cation-π interaction along with conventional non-covalent interactions would provide deep insights for understanding the stability of protein structures.     

Preparation and characterization of a new coagulant based on the sago starch biopolymer and its application in water turbidity removal

A new organic coagulant, sago starch (SS)‐graft‐polyacrylamide (PAm), was prepared by the ceric‐ion‐induced redox polymerization of acrylamide (Am) onto SS at room temperature. The effects of the variation of the concentration of Am and the initiator on the percentages of yield and total conversion were investigated. The chemical composition, viscosity, and side‐chain‐average molecular weight of the obtained graft copolymers were determined. The newly obtained coagulant was tested for the treatment of the turbidity of water. The SS‐g‐PAm coagulants were found to achieve water turbidity removal up to 96.6%. The results of this study suggest that SS‐g‐PAm copolymer is a potential coagulant for reducing turbidity during water treatment. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci 2008     

Microencapsulation of cashew apple (Anacardium occidentale,L.) juice using a new chitosan–commercial bovine whey protein isolate system in spray drying

The aim of this work was to obtain a new stable food product from cashew apple juice encapsulated by spray-drying technique using chitosan–whey protein isolate systems. The materials were evaluated according to their physicochemical stability during storage at different conditions and characterized with respect to their particle size distribution and structure. Encapsulated commercial and natural juices showed homogenous and unimodal particle size distribution with diameters ranging from 0.2 to 5.0 μm and from 0.2 to 40.0 μm, respectively. Both juices demonstrated higher physicochemical stability for vitamin C and color measurements than their respective non-encapsulated juices. X-ray diffractograms evidenced that the powder juices after the 140th day of storage were still in amorphous state. These results indicate that the new product was effective in protecting sensitive compounds present in the food matrix and it was also able to remain stable throughout the study period.     

离子交换色谱-荧光检测法快速测定浓缩果汁中噻菌灵残留量

建立离子交换色谱-荧光检测法快速测定6种浓缩果汁中噻菌灵残留量的分析方法。样品直接用水稀释,采用LC-SCX离子交换色谱柱(25cm×4.6mm,5μm)分离,荧光检测器检测,以0.1mol/L磷酸二氢钾溶液(pH3.0)-乙腈(体积比为70∶30)为流动相,流速1.0mL/min,荧光激发波长307nm,发射波长359nm。样品中噻菌灵能得到良好的分离,在0.001￣0.1mg/L范围内峰面积与质量浓度呈良好的线性关系(r为0.9999),回收率及重现性良好。方法简便、快速、灵敏、准确,可用于浓缩果汁中噻菌灵残留的检测。     

Effects of different thermal treatments and storage on the proximate composition and protein quality in canned tuna

The purpose of this project was to study the modifications in nutrient composition, amino acid content, and protein quality of white tuna preserves after each of the thermal treatments involved in the canning process. Also the influence that a three years storage period at room temperature has on the nutritional quality of canned tuna was studied. The biological assays used for the study of the protein utilization were carried out on Wistar rats, fed on semi-synthetic diets for 12 days varying only the protein source, casein or tuna provided as follows: raw, cooked in brine, steamed, sterilized tuna, and canned tuna stored for three years. The sterilization process and storage time led to a great increase in the lipid content of the canned tuna and to a porcentual decrease in protein, and moisture content. Amino acid composition of canned and cooked tuna did not show great modifications compared to raw tuna. Neither protein digestibility nor biological value of the cooked, canned, and stored tuna showed any deterioration. The protein quality of white tuna meat preserves has been compared with preserves made up of red and white tuna meat.     

Structure of decrystallized cotton in fabrics prepared by alkali and acrylonitrile treatments

The crystalline structure of decrystallized cotton, prepared by partial cyanoethylation with the use of sodium hydroxide aqueous solution and acrylonitrile, was examined by x-ray and IR data, in connection with such fabric properties as moisture regain. It was found that the moisture regain of the cotton fabric first increased, passed through a maximum at about 6 mole-% of cyanoethylation, and then slightly decreased with increasing degree of cyanoethylation. The increase of moisture regain in the region of the lower degree of cyanoethylation was well related to the decrease in the crystallinity of cotton. The x-ray diffraction studies revealed that the distension and disorder of the unit cell occurred primarily in the direction perpendicular to the (101) crystal plane as cyanoethylation proceeded.     

Pathway focused protein profiling indicates differential function for IL-1B, -18 and VEGF during initiation and resolution of lung inflammation evoked by carbon nanoparticle exposure in mice

Background  

Carbonaceous nanoparticles possess an emerging source of human exposure due to the massive release of combustion products and the ongoing revolution in nanotechnology. Pulmonary inflammation caused by deposited nanoparticles is central for their adverse health effects. Epidemiological studies suggest that individuals with favourable lung physiology are at lower risk for particulate matter associated respiratory diseases probably due to efficient control of inflammation and repair process. Therefore we selected a mouse strain C3H/HeJ (C3) with robust lung physiology and exposed it to moderately toxic carbon nanoparticles (CNP) to study the elicited pulmonary inflammation and its resolution.     

A new modified multiwalled carbon nanotube paste electrode for quantification of tin in fruit juice and bottled water samples

In this paper, a new modified multiwalled carbon nanotube electrode is reported for anodic stripping voltammetry quantification of tin. The electrode is based on the use of N-Nitrozo-N-Phenylhydroxylamine (cupferron) and multiwalled carbon nanotube. The influence of supporting electrolytes, deposition time, and applied potential on the sensitivity of electrode were investigated. The detection limit was 0.12 ng/ml and the RSD at a concentration level of 50 ng/ml, was 1.5%. The electrode has been applied for the determination of tin in fruit juice and bottled water with the satisfactory results.     

GC联合GC-MS测定果蔬汁中11种有机磷农药的残留量

建立了气相色谱仪(GC)与气相色谱质谱联用仪(GC-MS)结合测定果蔬汁中11种有机磷农药残留量的分析方法。优化了样品前处理方法,同时优化了GC与GC-MS分析条件。样品以乙酸乙酯提取,添加氯化钠与无水硫酸镁优化萃取条件,以GCB/PSA小柱净化后供GC和GC-MS分析。该方法简便、快速、准确,11种有机磷农药在0.05~0.4 mg/L范围内,显示了良好的线性关系,相关系数均大于0.995,平均加标回收为81.29%~111.74%,回收实验的相对标准偏差(RSD,n=6)在1.9%~8.6%之间。     

Different roles of electrostatics in heat and in cold: adaptation by citrate synthase

Electrostatics plays a major role in heat adaptation by thermophilic proteins. Here we ask whether electrostatics similarly contributes to cold adaptation in psychrophilic proteins. We compare the sequences and structures of citrate synthases from the psychrophile Arthobacter Ds2-3R, from chicken, and from the hyperthermophile Pyrococcus furiosus. The three enzymes share similar packing, burial of nonpolar surface area, and main-chain hydrogen bonding. However, both psychrophilic and hyperthermophilic citrate synthases contain more charged residues, salt bridges, and salt-bridge networks than the mesophile. The electrostatic free-energy contributions toward protein stability by individual charged residues show greater variabilities in the psychrophilic citrate synthase than in the hyperthermophilic enzyme. The charged residues in the active-site regions of the psychrophile are more destabilizing than those in the active-site regions of the hyperthermophile. In the hyperthermophilic enzyme, salt bridges and their networks largely cluster in the active-site regions and at the dimer interface. In contrast, in the psychrophile, they are more dispersed throughout the structure. On average, salt bridges and their networks provide greater electrostatic stabilization to the thermophilic citrate synthase at 100 degrees C than to the psychrophilic enzyme at 0 degrees C. Electrostatics appears to play an important role in both heat and cold adaptation of citrate synthase. However, remarkably, the role may be different in the two types of enzyme: In the hyperthermophile, it may contribute to the integrity of both the protein dimer and the active site by possibly countering conformational disorder at high temperatures. On the other hand, in the psychrophile at low temperatures, electrostatics may contribute to enhance protein solvation and to ensure active-site flexibility.     

Composites formed by interstitial polymerization of vinyl monomers in polyurethane elastomers: 6. Low angle X-ray scattering and turbidity

Low angle X-ray scattering (LAXS) from an interstitially polymerized poly(methyl methacrylate)-polyurethane system has been analysed in terms of a model due to Debye to give the mean chord intercept lengths of the disperse phase (PMMA) and matrix (PU). The model was found to fit the scattering within the experimental errors and the results are in excellent agreement with the results of electron microscopy. A theoretical expression is derived relating the turbidity with (a) the difference in refractive indices between the polyvinyl and polyurethane phases, (b) the size of the two phase domain structure, and (c) the volume fraction of the phases. The expression has been tested experimentally. The domain sizes derived from the turbidity equation agree reasonably with those observed by LAXS and electron microscopy.     

Possible roles of cotton bud sugars and terpenoids in oviposition by the boll weevil

Several cottonGossypium spp. race stocks have been identified that possess resistance to the boll weevilAnthonomus grandis Boh. because oviposition is decreased. In this work, a number of known cotton constituents that influence stimulation of feeding and attractancy for this insect were found to have little or no influence on oviposition. These include gossypol, -bis-abolol, caryophyllene, some fatty acids and their methyl esters, some wax esters, flavonoids, condensed tannins, and chrysanthemin. Analysis of cotton bud surfaces showed that the content of volatile terpenoids was generally higher in resistant lines, but bioassays did not show decreased oviposition in the presence of the terpenoids. The sugars (glucose, fructose, and sucrose) found in anthers, uniformly stimulated oviposition in the bioassay, and their content was higher in susceptible lines. These results suggest that a major basis of resistance to boll weevils as related to oviposition may be the decreased content of sugars in resistant lines. The analysis of free sugars in the anthers, and perhaps also the analysis of bud surface terpenoids, may provide a basis for selection or genetic production of cotton lines resistant to the boll weevil.