固体碱KF/CeO2催化大豆油制备生物柴油的研究

以硝酸铈铵为铈源，采用水热法制备CeO₂载体，浸渍法制备KF/CeO₂固体碱催化剂，并采用X射线衍射(XRD)、扫描电镜(SEM)和比表面积(BET)对催化剂进行表征。结果表明：KF/CeO₂固体碱对大豆油制备生物柴油有催化作用；催化剂的最佳制备条件为KF负载量40%、焙烧温度500℃、焙烧时间3 h;制备生物柴油的最佳反应条件为催化剂用量为大豆油质量的3.0%、醇油摩尔比9∶1,在该条件下生物柴油的最高产率为86.7%。     

Li掺杂CeO2固体碱催化甘油酯交换合成碳酸甘油酯

针对由甘油制备碳酸甘油酯的酯交换法中催化剂制备方法复杂、活性组分易流失等问题,采用一锅法制备了Li掺杂CeO₂固体碱催化剂。对催化剂进行了X射线衍射(XRD)、扫描电镜(SEM)、透射电镜(TEM)、BET、X射线光电子能谱(XPS)、CO₂程序升温脱附(CO₂-TPD)等表征。以甘油转化率和碳酸甘油酯产率为指标,对催化剂进行了筛选,并采用单因素实验对甘油酯交换合成碳酸甘油酯的工艺条件进行了优化,同时考察了催化剂的重复使用性能。结果表明：Li与CeO₂之间能够产生协同作用,Li的掺杂能够明显增加CeO₂的中强碱活性位点;Li、Ce与柠檬酸物质的量比为0.3∶1∶1时,催化剂催化活性最好;甘油酯交换合成碳酸甘油酯的最优反应条件为反应温度100℃、反应时间2.0 h、催化剂用量为甘油质量的1%、甘油与碳酸二甲酯物质的量比1∶2,在此条件下甘油转化率为90.16%,碳酸甘油酯收率为90.04%;催化剂在重复使用5次后活性无明显下降。采用一锅法制备的Li掺杂CeO₂     

Cu/Ce0.75Zr0.25O2催化剂制备及其催化乙醇干气重整反应性能研究

采用微波辅助尿素共沉淀法制备Cu/Ce_0.75Zr_0.25O₂催化剂,并使用Cu/Ce_0.75Zr_0.25O₂催化剂催化乙醇干气重整反应。试验结果表明,该催化剂具有较高的催化活性,且随反应温度的升高而增大,750℃下反应90h后,其催化剂活性保持稳定,乙醇转化率仍保持100%。     

固体碱催化剂Na2SiO3/MgO催化大豆油合成生物柴油的研究

以MgO为载体，采用等体积浸渍法制备固体碱催化剂Na₂SiO₃/MgO。通过X射线衍射(XRD)和傅里叶变换红外光谱(FT-IR)分别对催化剂和产物进行表征。通过单因素试验和正交试验优化了大豆油制备生物柴油的工艺条件。结果表明：当Na₂SiO₃/MgO中的Na₂SiO₃负载量为20%(以MgO质量计)、醇油摩尔比为10∶1、催化剂用量4%(以大豆油质量计)、反应温度55℃、反应时间3h时，生物柴油的产率可以达到98.77%。XRD表征结果表明，当Na₂SiO₃的负载量为20%时，Na₂SiO₃以单层分散的形式附着在载体MgO表面，且没有形成新的晶体。FT-IR表征结果表明，所合成产物分子的官能团结构与目的产物相符。     

Ag6Si2O7/TiO2 复合光催化剂的制备及其对亚甲基蓝的降解性能

为制备具有稳定性能的可见光催化剂,采用原位沉积法制得Ag₆Si₂O₇/TiO₂复合可见光催化剂。对光催化剂的表面形貌、结晶结构、化学元素组成和荧光光谱进行分析。在可见光照射下,以亚甲基蓝为有机污染物模型,探讨了TiO₂质量分数对复合光催化剂光催化降解效率的影响。结果表明:Ag₆Si₂O₇/TiO₂复合光催化剂中,Ag₆Si₂O₇均匀地包覆在TiO₂表面,二者以核壳结构形式紧密结合,且Ag、Si和Ti是以Ag⁺、Si⁴⁺和Ti⁴⁺存在;与纯Ag₆Si₂O₇和纯TiO₂相比,Ag₆Si₂O₇/TiO₂光催化剂具有更高的可见光光催化活性;当TiO₂质量分数为20%时,对亚甲基蓝降解效果最佳,在20 min内降解率达到98.6%。这种新型高效复合可见光催化剂可用于处理印染废水,具有广阔的应用前景。     

磁性固体碱K2O/LDO-γ-Fe2O3催化甘油合成碳酸甘油酯

为了解决甘油合成碳酸甘油酯产率较低及反应完成后催化剂的回收问题,制备磁性水滑石LDH-Fe₃O₄,以KNO₃为活性组分前驱体对其改性制备磁性固体碱催化剂K₂O/LDO-γ-Fe₂O₃,对KNO₃的负载量进行考察,对K₂O/LDO-γ-Fe₂O₃进行X射线衍射、扫描电子显微镜、 CO₂程序升温脱附、BET及磁化强度表征,采用单因素试验对K₂O/LDO-γ-Fe₂O₃催化甘油酯交换合成碳酸甘油酯的工艺条件进行了优化,并对K₂O/LDO-γ-Fe₂O₃的重复使用性能进行了考察。结果表明：KNO₃负载提供了大量的碱性位点,有利于催化剂催化活性的提高,KNO₃的最佳负载量为10%(以L...     

哌嗪基改性低黄变硅油的制备与性能

以线性体WS-62M、γ-哌嗪丙基甲基二甲氧基硅烷为反应原料,以氢氧化钾为催化剂,通过酯交换反应和缩聚反应合成哌嗪基改性氨基硅油。介绍了氨基硅油的黄变机理和改性方法,分析了反应原料的选择、催化剂、氮气、反应时间和温度等反应条件对改性硅油合成的影响,探讨了乳化对硅油性能的影响,测试并比较了几种硅油的基本性能、稳定性、手感、白度和亲水性。得出最佳反应条件为:反应温度85℃,催化剂用量0.3‰,酯交换反应时间3h,缩聚反应2h。合成的哌嗪基改性氨基硅油外观较为透明,稳定性和亲水性有所增加,基本无黄变,白度和柔软性有所提高。     

微杆菌XL1左聚糖酶的发酵条件优化及酶学性质研究

为提高微杆菌XL1左聚糖酶的产量,采用单因素试验和响应面试验对微杆菌XL1的产酶发酵条件进行优化,并对左聚糖酶的酶学性质和水解产物进行分析。优化结果表明,微杆菌XL1的最佳产酶条件为左聚糖3.4 g/L,酵母粉3.8 g/L,FeSO₄·7H₂O 0.01 g/L,CaCl₂ 0.1 g/L,KH₂PO₄1 g/L,MgCl₂ 0.15 g/L,初始pH值6.0,接种量4%,25℃、180 r/min培养30 h。在此条件下,微杆菌XL1发酵液酶活力达到3.47 U/mL,相比优化前提高了298%。酶学性质分析表明,左聚糖酶的最适反应温度为55℃,最适反应pH为5.5;在40～50℃、pH 5.0～7.0时酶活力较稳定;Co²⁺、 Ca²⁺和Mn²⁺能显著提高酶活力;Cu²⁺、 Ni²⁺、 Zn²⁺和EDTA对酶有较强的抑制作...     

Fe基类Fenton催化剂非均相处理造纸废水

针对传统均相Fenton法深度处理造纸废水中铁泥量大、成本较高等问题,将Fe₂O₃、Al₂O₃、SiO₂、石墨粉采用高温烧结的方式,制备Fe基类Fenton催化剂,并用于非均相Fenton处理造纸废水,可达到节省FeSO₄用量的效果。结果表明,经高温烧结制备的Fe基类Fenton催化剂具有丰富的孔隙结构,在pH值为3、催化剂投加量15 g/L、COD_Cr和H₂O₂质量比1∶0.75、反应时间90 min的条件下,造纸废水COD_Cr去除率为74.8%,且经过10次循环实验仍达70%以上,BOD₅去除率可达67%以上。     

杂多酸离子液体催化棉籽油制备生物柴油研究

制备了5种杂多酸离子液体催化剂[TEA-PS]_XH_3-XPW₁₂O₄₀(X=1,1.5,2,2.5,3),用于催化棉籽油酯交换制备生物柴油研究,其中杂多酸离子液体[TEA-PS]_1.5H_1.5PW₁₂O₄₀的催化活性最高。以杂多酸离子液体[TEA-PS]_1.5H_1.5PW₁₂O₄₀为催化剂,研究了甲醇与棉籽油摩尔比、催化剂[TEA-PS]_1.5H_1.5PW₁₂O₄₀用量、反应温度和反应时间对甲醇与棉籽油酯交换反应的影响。结果表明:当甲醇与棉籽油摩尔比为12∶1、催化剂[TEA-PS]_1.5H_1.5PW₁₂O₄₀用量为棉籽油质量的5%、反应温度80℃、反应时间6 h时,生物柴油收率最高,达95.3%;同时,催化剂[TEA-PS]_1.5H_1.5PW₁₂O₄₀重复使用6次后,生物柴油收率仍高于92%。     

Effects of SO2 on sulphur and nitrogen fractions and on free amino acids in perennial ryegrass

An investigation was made of the S and N fractions and of the free amino acids in the shoots of perennial ryegrass (Lolium perenne L.) cv S23 grown in soil with and without added sulphate and in filtered air containing 0 and 400 μg SO₂ m^?3. Exposure to SO₂ of potentially S-deficient plants alleviated the signs of deficiency; compared to deficient plants, the content of total and sulphate S was increased and the ratio N:S, as well as content of free amino acids, including asparagine and glutamine, was decreased. Similar exposure of plants grown with an adequate supply of S through the soil increased the content of sulphate but resulted in no significant alteration of the content of free amino acids.     

WORT COMPOSITION AND BEER FLAVOUR. I. THE INFLUENCE OF SOME AMINO ACIDS ON THE FORMATION OF HIGHER ALIPHATIC ALCOHOLS AND ESTERS

Wort, to which was added various amounts of glucose solution containing either (NH₄)₂SO₄ or one of the amino acids alanine, leucine, isoleucine, valine or proline, was fermented, and in the resulting beers the concentrations of ethyl acetate, isoamyl acetate, n-propanol, isobutanol, and amyl alcohols were determined by gas chromatography. The nitrogen source had some effect on the formation of higher alcohols, in addition to the effect due to conversion of some of the amino acids to the corresponding alcohols via the Ehrlich pathway. Ethyl acetate formation was not significantly affected by the nitrogen source, and iso-amyl acetate formation increased when amyl alcohol formation increased.     

Nonenzymatic Nonoxidative Browning in Hydrolyzed Shelf-stable Concentrated Cheese Whey

The rate of brown color development in hydrolyzed concentrated cheese whey (HCCW), and in model systems of related composition, was studied. Degree of lactose hydrolysis was a relevant parameter controlling rate of color changes, both in modified whey or in related model systems. Added CaCl₂ had a strong inhibitory effect on caramelization browning in model systems in which no amino compounds were added. This inhibitory effect was less important in model systems containing whey proteins and in HCCW in which Maillard's browning is the main mechanism of darkening. Effects of pH and temperature were similar to that previously reported for nonhydrolyzed concentrated cheese whey, as well as for many model systems containing sugars and amino acids.     

FRANKFURTERS SUPPLEMENTED WITH CORN GERM PROTEIN: SENSORY CHARACTERISTICS,PROXIMATE ANALYSIS AND AMINO ACID COMPOSITION1

Defatted corn germ protein (CGP) has been studied as a functional or substitute ingredient of frankfurters. The proximate composition (protein, fat, moisture, ash) and amino acid content of hexane- and supercritical-CO₂-defatted CGP and frankfurters containing CGP were determined. CGP was incorporated in frankfurters as in a powder, slurry form and as a stabilizer of emulsions. Proximate analysis showed significantly lower fat content of CGP processed by a modified procedure and a reduction of fat content in meats containing CGP. Levels of essential amino acids in CGP compared favorably to those in sodium caseinate, hen's egg protein, and soybean protein. Except for isoleucine, CGP meets or exceeds a FAO provisional amino acid pattern recommended for human consumption. No significant differences were found in amino acid composition of hexane- or supercritical-CO₂-defatted CGP. Amino acid composition of frankfurters was not greatly altered by the addition of CGP at the levels studied. An acceptable, weak corny aroma and taste could be detected at 2.4 and 3.5% levels of added CGP. Defatted CGP with its high protein content and amino acid pattern combined with relatively low cost has potential as an extender, fortifier, and binding agent in frankfurters and other comminuted meats.     

Inhibition of 2‐Amino‐1‐methyl‐6‐phenylimidazo [4,5‐b]pyridine (PhIP) Formation by Alkoxy Radical Scavenging of Flavonoids and Their Quantitative Structure–Activity Relationship in a Model System

The inhibitory effect of 10 flavonoids on the formation of 2‐amino‐1‐methyl‐6‐phenylimidazo[4,5‐b]pyridine (PhIP) in a creatinine–phenylalanine model system was investigated through electronic spin resonance and a quantitative structure–activity relationship. Alkoxy radicals were observed during the heating process, providing evidence for a radical pathway in the formation of PhIP. The alkoxy radical scavenging capability of the flavonoids was proportional to their inhibition of PhIP formation (IC₅₀). We deduced that flavonoid inhibition of PhIP generation occurs via scavenging of alkoxy radicals during the heating process. Multiple linear regression and partial least squares models were used to elucidate the relationship between PhIP inhibition activity and structure characteristics of the flavonoids. The lipo–hydro partition coefficient and molecular fractional polar surface area of the flavonoids were found to be predictive of the inhibition effect.     

Free-Volume Changes in Flexible, Hermetic Packages Containing Respiring Produce

To investigate free-volume changes in flexible, sealed packages containing respiring fruits and vegetables, a simple method based on the dilution of an injected gas (ethane) in the package was developed. Free-volume decreased steadily at ～3 cm³/day after an initial transient period in low-density polyethylene packages (29-μm-thick film; 600-cm² surface area; initial free volume ～285 cm³) containing 40g of cut broccoli held at 0°C. A general transient model was developed that showed that free-volume changes in flexible packages were a function of differential film O₂, CO₂, and N₂ permeabilities and differential product O₂ uptake and CO₂ production rates. The model predicted that flushing packages with low permeative gases would decrease free-volume depletion rate, whereas flushing with highly permeative gases, such as CO₂, would increase the initial rate considerably.     

ELECTROSTATIC EFFECTS ON PHYSICAL PROPERTIES OF PARTICULATE WHEY PROTEIN ISOLATE GELS

Physical properties of particulate whey protein isolate gels formed under varying electrostatic conditions were investigated using large strain rheological and microstructural techniques. The two treatment ranges evaluated were adjusting pH (5.2‐5.8) with no added NaCl and adjusting the NaCl (0.2‐0.6 M) at pH 7. Gels (10% protein w/v) were formed by heating at 80C for 30 min. The large strain properties of fracture strain (γ_f), fracture stress (σ_f), and a measure of strain hardening (R_0.3) were determined using a torsion method. Gel microstructure was evaluated using scanning electron microscopy (SEM) and gel permeability (B_gel). Overlaying σ_f and γ_f curves for pH and NaCl treatments demonstrated an overlap where gels of equal σ_f and γ_f could be formed by adjusting pH or NaCl concentration. The high fracture stress (σ_f～ 23 kPa and γ_f～ 1.86) pair conditions were pH 5.47 and 0.25 M NaCl, pH 7.0. The low fracture stress (σ_f～ 13 kPa and γ_f～ 1.90) pair conditions were pH 5.68 and 0.6 M NaCl, pH 7.0. The 0.25 M NaCl, pH 7 treatment demonstrated higher R_0.3 values than the pH 5.47 treatment. When the sulfhydryl blocker n‐ethylmaleimide was added at 2 mM to the 0.25 M NaCl, pH 7 gel treatment, its rheological behavior was NSD (p>0.05) to the pH 5.47 gel treatment, indicating disulfide bond formation regulated strain hardening. Altering surface charge or counterions, and disulfide bonding, was required to produce gels with similar large strain rheological properties. An increase in gel permeability coincided with an increase in pore size as observed by SEM, independent of rheological properties. This demonstrated that at the length scales investigated, microstructure was not linked to changes in large strain rheological properties.     

Effects of pH, CaCl2 and Soy Protein on [Ca2+] in Reconstituted Nonfat Dry Milk and on Rennet-Induced Coagulum Properties

Increasing CaCl₂ and lowering pH caused a significant increase in [Ca²⁺] in reconstituted nonfat dry milk (RNDM), while the addition of soy protein caused a significant reduction in [Ca²⁺]. Lowering pH greatly increased rennet-induced coagulum firmness in RNDM and slightly increased it in RNDM-soy protein mixtures. Added CaCl₂ increased coagulum textural parameters and syneresis in both systems. The extent to which these properties were increased was higher in RNDM than in the coagulum containing soy protein depending on the time after rennet addition and the amount of CaCl₂ added. The first increment of CaCl₂ added had the highest effect in improving textural properties and increasing syneresis.     

Effects of nitrogen and sulphur fertilisers on the yield, N and S content, and amino acid composition of the grain of spring wheat.

Spring wheat (cv. Kleiber) was grown in three pot experiments in a soil containing 10 mg kg^?1 KH₂PO₄-soluble sulphur with different rates of nitrogen and sulphur fertilisers. Without added S the yields of grain dry matter and crude protein were either unchanged (glasshouse experiment) or significantly decreased by the N treatments (controlled environment experiments). With added S the N fertiliser increased the yields by 40–110%. The experiments produced grain with a wide range of N and S contents, the latter ranging from 0.06–0.21% on a dry matter basis. Grain from treatments giving the largest yields of dry matter and crude protein had a N:S ratio of about 15. The amino acid composition of the whole grain was changed significantly by the fertiliser treatments. When plants were grown without added S at the highest level of N the grain contained less than half the amount of cyst(e)ine and methionine (as % of total amino acid content) found in grain from plants given adequate amounts of S fertiliser. Grain from S-deficient plants also had a much greater content of aspartic acid + asparagine but less threonine, leucine, isoleucine and lysine. The N:S ratio in grain from plants grown with insufficient S was well in excess of 15. The relation of these findings to the nutritive value of wheat as a feed and to the provision of enough disulphide bonding capacity for its use in bread-making are discussed. Our results emphasise the necessity for having an adequate amount of S to balance the larger N applications now given to wheat to ensure that the grain is of the highest quality possible with any particular cultivar.     

Tissue distribution and elimination of deoxynivalenol and ochratoxin A in dietary-exposed Atlantic salmon (Salmo salar)

ABSTRACT

Post-smolt Atlantic salmon (Salmo salar) were fed standard feed with added 2 or 6 mg kg^–1 pure deoxynivalenol (DON), 0.8 or 2.4 mg kg^–1 pure ochratoxin A (OTA), or no added toxins for up to 8 weeks. The experiments were performed in duplicate tanks with 25 fish each per diet group, and the feed was given for three 2-h periods per day. After 3, 6 and 8 weeks, 10 fish from each diet group were sampled. In the following hours after the last feeding at 8 weeks, toxin elimination was studied by sampling three fish per diet group at five time points. Analysis of DON and OTA in fish tissues and plasma was conducted by liquid chromatography-mass spectrometry and high-pressure liquid chromatography with fluorescence detection, respectively. DON was distributed to the liver, kidney, plasma, muscle, skin and brain, and the concentrations in liver and muscle increased significantly from 3 to 8 weeks of exposure to the high-DON diet. After the last feeding at 8 weeks, DON concentration in liver reached a maximum at 1 h and decreased thereafter with a half-life (t_1/2) of 6.2 h. DON concentration in muscle reached a maximum at 6 h and was then eliminated with a t_1/2 = 16.5 h. OTA was mainly found in liver and kidney, and the concentration in liver decreased significantly from 3 to 8 weeks in the high-OTA group. OTA was eliminated faster than DON from various tissues. By using Norwegian food consumption data and kinetic findings in this study, we predicted the human exposure to DON and OTA from fish products through carryover from the feed. Following a comparison with tolerable daily intakes, we found the risk to human health from the consumption of salmon-fed diets containing maximum recommended levels of these toxins to be negligible.