To improve robustness of mechanical properties of semi-solid cast A356 alloy using taguchi design method

Mechanical properties of semi-solid casting are dependent on multiple processing parameters,and improper processing parameters will not only reduce mean data but also increase variations.The present study investigated the impact of parameters in slurry preparation and heat treatment on the yield strength and ductility of T6 heat-treated A356 Al-Si alloy using rapid slurry forming(RSF)semi-solid casting.The focus was primarily on the robustness of mechanical properties based on Taguchi design method.By analyzing signal-to-noise ratio and minimum value calculated from-3S,the optimum slurry preparation parameters and heat treatment parameters were determined to be no quench,enthalpy exchange material(EEM)temperature of 140℃,EEM-to-melt ratio of 6mass%,stirring time of 18 s,solution heat treated at 520℃ for 2 h,and ageing heat treated at 190℃ for 6 h.In a small batch validation,the-3S yield strength and-3S elongation reach 256.1 MPa and 5.03% respectively,showing a satisfactory robustness.The hardness and microstructure of heat-treated samples with the best and worst properties were characterized to gain insight into the underlying mechanisms affecting the mean value and variations of mechanical properties.

Microstructure evolution of Ti_(48)Zr_(27)Cu_(6)Nb_(5)Be_(14)amorphous alloy after semi-solid isothermal treatment

The as-cast amorphous Ti_(48)Zr_(27)Cu_(6)Nb_(5)Be_(14)composites,comprising in situ formedβ-Ti ductile crystalline precipitates,were prepared by water cooled copper mold suction casting.Then,the semi-solid composites were obtained after the as-cast composites were treated by semi-solid isothermal treatment.The microstructure evolution and kinetics of the composites were examined.Results show that the microstructures of both the as-cast and semi-solid composites comprise ofβ-Ti crystal phases and amorphous matrix phases.Before and after treatment,the crystals evolve from fine granular or fine dendritic crystals to coarse crystals.As the treatment temperature increasing or the time prolonging,the average crystal size gradually increases and the surface morphology of the crystals gradually becomes regular.By studying the microstructural evolution and dynamics during the isothermal treatment process,it is found that the final morphology ofβ-Ti crystals is influenced by the isothermal treatment temperature and time(t),and theβ-Ti evolution rate increases with an increase in treatment temperature.In addition,a linear relationship was observed between the size of cubicβ-Ti crystals(D^(3))and t;the growth kinetics factor K is 3.8μm^(3)·s^(-1).As the K value closes to 4μm^(3)·s^(-1),it is inferred the morphology evolution ofβ-Ti crystals is a coarsening behavior controlled by the diffusion of solute elements.

Treatment of Enzymolysis Wastewater by Centrifugation- Coagulation- Fenton Reagent Oxidation- Adsorption Process

[ Objective ] The study aimed to discuss the optimal conditions for the treatment of enzymolysis wastewater by centrifugation - coagu- lation - Fenton reagent oxidation - adsorption process. [ Metbod] According to the water-quality characteristics of wastewater from a heparin so- dium production factory of Jiangsu Province, enzymolysis wastewater was segregated from intestinal lavage wastewater and treated through cen- trifugation- coagulation- Fenton reagent oxidation-adsorption process, and the optimal technical parameters were determined. E Resultl After enzymolysis wastewater was centrifuged at a speed of 4 000 rpm, 0.6 g/L CTS as the coagulant was added to the supematant. Hereafter, pH of the coagulated effluent was adjusted to 3, and then 1.5% （V/V） H2O2 was added to the coagulated effluent; a certain amount of ferrous sul- fate （n H2O2-.n FeSO4 . 7H2O =8：1 ） was added to the mixture; the reaction conducted for 30 min, and then solution pH was adjusted to about 9. Finally, the oxidized effluent flowed through a resin red until the adsorptive capacity reached 240 BV, and COD of the effluent water was lower than 100 mg/L, meeting the Grade-I standard of Comprehensive Discharge Standard of Sewage （GB8978-1996）. [Condusio] The research could provide a new process for the treatment of enzymolysis wastewater.

Oxidative depolymerization of lignin improved by enzymolysis pretreatment with laccase

A new lignin depolymerization approach for improving the yield of aromatic monomers（YAM） by enzymolysis pretreatment was investigated, in which lignin was pretreated with laccase followed by oxidative depolymerization. It was found that lignin depolymeirzation was enhanced significantly by enzymolysis. The oxidative depolymerization contributed to 21.37% of YAM after the enzymolysis pretreatment,whereas the conventional oxidative depolymerization only gave 14.10% of YAM. The addition of ethanol in enzymatic pretreatment process improved the efficiency of enzymolysis, which effectively improved the solubility of pretreated lignin and depolymerization degree（DD） of lignin. The enzymolysis pretreatment increased the content of syringyl（S） style aromatic monomers, which hindered the recondensation among polymerized products. As lignin has low solubility in acidic aqueous solution, ethanol was added into enzymolysis system to improve the efficiency. However, the enzymolysis of lignin should be carried out for a limited period of time to prevent the inactivation of laccase.

Mechanical properties and microstructural evolution of rheocast A356 semi-solid slurry prepared by annular electromagnetic stirring

Nowadays,having an effective technique in preparing semi-solid slurries for rheocasting process seems to be an essential requirement.In this study,semi-solid slurry of A356 aluminum alloy was prepared by three-phase annular electromagnetic stirring(A-EMS)technique under different conditions.The effects of stirring current,pouring temperature and stirring time on microstructural evolution,mean particle size,shape factor and solid fraction were investigated.The rheocasting process was carried out by using a drop weight setup and to inject the prepared semi-solid slurry in optimal conditions into the step-die cavity.The filling behavior and mechanical properties of parts were studied.Microstructural evolution showed that the best semi-solid slurry which had fine spherical particles with the average size of~27μm and a shape factor of~0.8 was achieved at the stirring current of 70 A,melt pouring temperature of 670℃,and stirring time of 30 s.Under these conditions,the step-die cavity was completely filled at die preheating temperature of 470℃.The hardness increases by decreasing step thickness as well as die preheating temperature.Moreover,the tensile properties are improved at lower die preheating temperatures.The fracture surface,which consists of a complex topography,indicates a typical ductile fracture.

Microstructure characteristics and thermodynamic properties of A357-SiCp/A357 layered composites prepared by semi-solid vacuum stirring suction casting

A357-SiCp/A357 layered composites were prepared using a semi-solid vacuum stirring suction casting method.The microstructures,mechanical properties,and thermal conductivities of the composites fabricated under different suction casting processes were compared.Additionally,the microstructural evolution characteristics and performance enhancement mechanism of the A357-SiCp/A357 layered composites were discussed.The results demonstrate that suction casting at 610°C with a low solid phase ratio can significantly enhance the material density and reduce the agglomeration of SiCp.The A357-SiC_(p)/A357 interface is clear and straight with good bonding.With an increase in the suction casting temperature,the bending resistance and thermal conductivity of the A357-SiC_(p)/A357 layered composites exhibit a trend of significantly increase at first and then slowly decrease owing to casting defects,interface bonding,and SiCp distribution.Compared with SiCp/A357 composites,the bending strength,deflection,and thermal conductivity of the A357-SiCp/A357 layered composites increase from 257 MPa,1.07 mm,and 155.72 W·(m·K)^(-1) to 298 MPa,2.1 mm,and 169.86 W·(m·K)^(-1),respectively.This study provides a reference for improving the rheological casting of aluminum matrix layered composites.

植物蛋白肉感官品质与营养安全研究进展

综述了植物蛋白肉在外观、口感、风味方面的技术进步,分析了植物蛋白肉营养稍逊肉类的原因以及改善途径,论述了植物蛋白肉的安全性,以期为高品质植物蛋白肉加工提供理论参考。

血栓通对阿尔茨海默症模型小鼠认知功能及神经异常兴奋性的作用及其机制研究

目的探究血栓通[主要有效成分为三七皂苷(panax notoginseng,PNS)]对阿尔茨海默症(Alzheimer’s disease,AD)模型小鼠认知功能及神经兴奋性的影响,并探讨其潜在分子机制。方法用APP/PS1小鼠作为AD研究动物模型,在小鼠淀粉样蛋白尚未检测到阶段(2月龄)开始每日以60 mg/kg对血栓通组(APP/PS1+PNS)行灌胃给药,每日1次,连续给药6个月(给药至8月龄);对照组小鼠予同等体积的0.9%氯化钠(APP/PS1+vehicle)灌胃处理,同月龄野生型小鼠予0.9%氯化钠灌胃处理作为正常对照组(WT+vehicle),每组各15只。6个月后,新物体识别实验、Morris水迷宫实验检测小鼠的认知功能;EEG脑电检测、Western blot、细胞表面生物素化试验以检测各组小鼠皮质与海马中BACE1的活性、Nav1.1α的分布、表达以及Navβ2的表达与酶解情况(Navβ2的酶解片段Navβ2 full length及Navβ2-CTF表达检测)。结果新物体识别实验显示,与对照组APP/PS1小鼠相比,血栓通用药后APP/PS1小鼠的辨别指数(discrimination index,DI)上升(P<0.05);Morris水迷宫检测结果发现,血栓通灌胃6个月后小鼠在探索实验中逃避潜伏期缩短(P<0.05),撤除平台后在目标象限停留时间增加(P<0.05)、穿梭平台次数增加(P<0.05);EEG脑电检测结果发现,血栓通给药后减少了APP/PS1小鼠棘波放电出现的频率(P<0.05)。血栓通给药后显著降低了BACE1蛋白水平的表达(P<0.05),而全长片段Navβ2的蛋白水平显著上升(P<0.05),并纠正了Nav1.1α在神经元内外的异常分布(P<0.05)。结论血栓通可以改善AD模型小鼠的学习记忆能力、纠正大脑异常兴奋性,其作用机制可能与抑制BACE1的活性从而减少Navβ2由APP/PS1诱导的过度酶解,纠正皮质、海马神经元Nav1.1α的异常表达与分布,调节神经元的兴奋性有关。

蓝圆鲹分离蛋白酶解产物的制备及其抗大米淀粉老化特性

为了进一步拓展海洋鱼类蛋白在食品中的应用,以蓝圆鲹分离蛋白为原料,利用酶解改性得到溶解性良好的蓝圆鲹分离蛋白酶解物(BPIH),并研究其对大米淀粉(RS)短期老化的抑制作用。通过响应面法优化酶解改性工艺制备BPIH,并分别按RS的3%、6%、9%(质量百分比)进行添加。通过测定RS的凝沉性、动态黏弹性、热学特性以及微观结构分析评价BPIH的抗淀粉老化活性。结果显示,响应面法确定的最佳条件:酶底比5000;1(U/g)、酶解时间3 h、料液比1.00;3.81、酶解温度46.36℃、酶解pH 6.30,氮溶指数(NSI)实际值为85.41%±0.82%,与预测值86.37%接近。该酶解条件下BPIH水解度达到21.62%。BPIH中小于1000 u的肽占79.94%,主要为小分子低聚寡肽。加入BPIH可以减弱RS的凝沉现象,降低RS在4℃保存过程中的储能模量(G'),显著降低老化后RS的峰值温度(T_(p))和焓值(ΔHr);加入BPIH的大米淀粉,老化后微观结构有较大孔洞,提升了淀粉糊化后保留内部水分的能力。研究表明,BPIH能够抑制RS在4℃保存期间凝胶网络和微晶结构的形成,同时可能限制了淀粉分子间的聚集,抑制或延缓RS的短期老化。本研究为蓝圆鲹分离蛋白酶解物在食品蛋白配料中的应用提供理论参考。

限制性酶解结合糖基化改性对大豆分离蛋白乳化性质的影响

目的:开发基于大豆分离蛋白(soybean protein isolate,SPI)的新型乳化剂。方法:采用限制性酶解结合糖基化处理对SPI进行结构修饰,研究协同改性对SPI乳化特性的影响。结果:SPI水解物(soybean protein isolate hydrolysate,SPIH)中的相对分子质量较大组分(F30)的乳化性最佳,且糖基化反应4 h的F30-葡聚糖轭合物乳化稳定性相对最好。相较于SPI,SPIH与F30,F30-葡聚糖轭合物稳定的乳液表现出最低的初始平均粒径,并且具有最佳的贮藏稳定性。当pH接近SPI等电点或体系处于高盐浓度时,所有乳液均出现不稳定聚集现象。与SPI相比,SPIH和F30稳定乳液的聚集程度更高,而F30-葡聚糖轭合物由于共价结合的葡聚糖提供了额外的空间位阻和亲水性,使得轭合物稳定的乳液能够耐受离子强度和温度的变化,在不利环境条件下表现出更高的抵抗力。结论:限制性酶解结合糖基化改性是开发SPI基乳化配料的潜在可靠途径。

压热及酶解脱支处理对莲藕淀粉品质的影响

淀粉是莲藕的主要成分。本研究通过压热处理、酶解脱支处理进行莲藕淀粉改性,并对其品质进行比较。结果发现:改性后莲藕淀粉中直链淀粉与碘结合能力显著增强,其中普鲁兰酶脱支处理莲藕淀粉(ELRS)的碘结合力最高,即可溶性直链淀粉含量最高;水合能力显著增强,其中压热法处理莲藕淀粉(HLRS)的持水性、持油性和膨胀度(21.766%)最高,析水率(14.300%)最低;压热后普鲁兰酶脱支处理莲藕淀粉(HELRS)的溶解度(63.555%)、透明度(0.717%)最高;改性后莲藕淀粉的糊化起始温度(T0)、热焓值(ΔH)、糊化温度(ΔT)均有所下降,其中HELRS的ΔH最低,表明改性后熔解莲藕淀粉所需的能量减少;检测改性后淀粉的凝胶特性表明,莲藕淀粉的硬度、弹性、内聚性、粘性和回弹性均有所下降。该研究结论为食品生产中针对不同需求进行淀粉改性提供了理论依据,并为莲藕淀粉的高附加值产品开发提供指导。

火麻仁黄嘌呤氧化酶抑制肽的酶解制备工艺研究

为寻找开发火麻仁蛋白,提高火麻应用价值的最佳条件,以火麻蛋白为原料,通过酶解法制备火麻仁黄嘌呤氧化酶抑制肽,采用正交试验法优化中性蛋白酶酶解火麻蛋白制备多肽的最佳工艺条件。以中性蛋白酶用量、酶解时间、酶解温度进行单因素试验,通过正交试验分析获得制备火麻仁黄嘌呤氧化酶抑制肽的最佳酶解条件为pH值6.5,料液比1∶5,酶用量6000 U/g,酶解温度50℃,酶解时间5 h。在此条件下进行的验证试验中,多肽抑制率为78.98%,表明该工艺稳定、可行,具有较高的应用价值。

酶解与发酵联合处理对牛蒡根风味的影响

用酶解和发酵联合处理新鲜牛蒡根,在活性多糖充分溶出的基础上,通过乳酸菌发酵改善牛蒡根的不良风味。以牛蒡酶解液中多糖含量和风味评分为指标,通过正交试验确定酶解最佳条件为:纤维素酶添加量4%,料液比1∶6,温度55℃,酶解时间1.5 h,超声功率200 W。气相色谱-质谱联用(GC-MS)分析显示,醛类及萜烯类化合物例如苯乙醛、Β-瑟林烯、A-姜黄烯是引起牛蒡不良风味的主要来源,在酶解、发酵过程中会转化为具有愉悦风味的酮类和醇类。主成分分析和聚类分析结果表明,经不同方式处理的牛蒡液中挥发性风味物质苯乙醛、Β-瑟林烯、A-姜黄烯存在较大差异,酶解与发酵联合处理可有效改善牛蒡根不良风味。

^(60)Co-γ射线辐照预处理聚乳酸改善厌氧发酵性能

聚乳酸(PLA)塑料垃圾沼气生产潜力大,但降解速率低,对其进行预处理可以提高其厌氧发酵效率,促进资源化。本文采用^(60)Co-γ射线对聚乳酸塑料杯样品进行辐照预处理,研究吸收剂量为0 kGy、20 kGy、40 kGy和60 kGy的照射下PLA分子结构及可溶性物质含量变化,并通过蛋白酶酶解实验和厌氧发酵产气量的变化研究电离辐照对其厌氧发酵性能的影响。结果表明:PLA样品经^(60)Co-γ射线辐照,PLA样品上清液中乳酸含量在0~60 kGy范围内随吸收剂量增加略微上升,样品的分子结构未发生明显改变,但辐照后其分子量和结晶度明显下降;辐照后样品在酶解过程中乳酸浓度和质量损失较未辐照样品有明显提升,其中吸收剂量为60 kGy的PLA样品在第4天的乳酸浓度达到最大值并比未辐照样品高17.4%,其质量损失随时间增加,在第7天比未辐照样品提升68.7%;辐照后的样品厌氧发酵达到产气平衡的时间明显缩短,总产气量提升3.0%。研究结果表明,γ射线辐照作为PLA塑料的预处理技术具有潜在的应用价值,本研究可为PLA塑料的资源化处置提供理论参考。

超声波辅助黄鳍金枪鱼免疫活性肽酶解工艺优化

本文以黄鳍金枪鱼肉为原料,通过超声波辅助酶解黄鳍金枪鱼肉制备免疫活性肽。以小鼠巨噬细胞相对增殖率为指标,筛选出最适蛋白酶为胰蛋白酶,并在单因素实验基础上,通过响应面优化试验确定了黄鳍金枪鱼肉的酶解条件。结果表明,酶解时间5 h、酶解温度37.6℃、超声波时间为11 min,在此条件下,小鼠巨噬细胞的相对增殖率最佳,为43.04%±2.03%,与线性回归模型的预测值相近。对最佳酶解条件下的黄鳍金枪鱼免疫活性肽进行氨基酸组成与分子量分析,其必需氨基酸为41.42%±1.24%,疏水氨基酸含量为26.49%±0.79%,分子量集中分布在4.7~6.5 kDa。研究结果为黄鳍金枪鱼的高值化利用提供了理论指导与技术支持。

酶解法脱糖提升黄骅冬枣脆片贮存稳定性的研究

黄骅冬枣糖分含量高,带给人们美味的同时也使黄骅冬枣脆片贮存期间易吸湿,出现黄骅冬枣脆片品质软化现象,明显的影响了黄骅冬枣脆片的口感。该文利用葡萄糖氧化酶作用对冬枣脆片进行部分脱糖处理,通过正交优化试验方法研究了酶解时间、酶添加量、酶解温度、料液比以及冬枣片厚度对冬枣脆片脱糖率及感官品质的影响,并通过等温吸附的方法研究了冬枣脆片的贮存稳定性。结果表明,在酶解时间为35 min,酶添加量0.15%(质量分数),酶解温度45℃,料液比1∶2(g∶mL),冬枣脆片厚度为10 mm条件下,冬枣脆片的脱糖率为43.30%,即还原糖含量为18.14%,与脱糖前冬枣脆片还原糖含量(32.00%)相比明显低,感官评分值为85.86分,综合评分值为98.98分。此条件下脱糖率最高,即还原糖含量降到最低,综合评分值达到了最高,冬枣脆片吸湿性能明显变弱,稳定性更好。该研究结果将为冬枣脆片相关产品的开发提供一定的理论及数据支持。

羊乳脂奶酪酱与牛乳脂奶酪酱风味机理对比分析

羊乳脂中含有丰富的中短链脂肪酸,可以赋予奶酪独特的风味,但目前对于羊乳脂在食品奶酪加工中的应用尚且不多。该文通过两步法制备羊乳脂奶酪酱(sheep milk fat cheese sauce,SMFCS)和牛乳脂奶酪酱(cow milk fat cheese sauce,CMFCS),验证羊乳脂代替牛乳脂在奶酪制备中的可行性。结果表明,羊乳脂中的中短链脂肪酸比牛乳脂中含量更高,且羊乳脂中没有检测到对羊膻味影响较大的支链脂肪酸,羊乳脂膻味较淡。采用气相色谱⁃质谱法鉴定CMFCS和SMFCS制备过程中挥发性化合物的动态变化,结果显示,CMFCS中共检测到53种挥发性化合物,SMFCS共检测到42种挥发性化合物,且SMFCS中醛醇类化合物在制备过程中比CMFCS检出少。电子鼻结果显示SMFCS比CMFCS和市售酶改性奶酪中苯类芳香成分、无机硫化物芳香成分及长链烷烃芳香成分含量更高。以上结果可为羊乳脂代替牛乳脂在奶酪中的应用提供参考。

超声波辅助酶解牦牛血粉提取氯化血红素的响应面工艺优化及品质表征

以牦牛血粉为原料,通过超声波辅助酶解技术提取氯化血红素,优化制备工艺并进行品质评价。以超声波辅助酶解时间、酶/底物浓度和超声比功率为自变量,以纯度为响应变量,采用Box-Behnken响应面设计优化提取工艺;通过紫外-可见分光光度计、色度仪、傅立叶转换红外光谱仪表征样品的纯度、得率、色度、化学结构等理化性质。结果表明,超声波辅助酶解时间、酶/底物浓度和超声比功率对氯化血红素提取物纯度均具有显著影响(P<0.05);经响应面优化后确定的最佳提取工艺为超声波辅助酶解时间4 h、酶/底物浓度17 U·mg^(-1)和超声比功率800 W·L^(-1),在此条件下氯化血红素提取纯度为14.89%,得率达63.30%。与普通酶解提取工艺相比,超声波辅助酶解提取得率和纯度分别提高1.29倍和1.07倍(P<0.05),提取样品的色度和化学结构与氯化血红素标准品更相近。综上所述,超声波辅助法(800 W·L^(-1)超声比功率下处理4 h)能在不改变理化性质的前提下显著提高从牦牛血粉中酶解提取氯化血红素的纯度和得率。

羊肉蛋白酶解工艺优化及酶解液中氨基酸含量分析

采用新疆阿勒泰羊后腿肉为原料,以蛋白酶添加比例、酶解时间、pH值及酶解温度为自变量,以蛋白水解度为评价指标,采用单因素和响应面试验探究木瓜蛋白酶与风味蛋白酶组成的复合酶最佳酶解条件,并测定酶解液中氨基酸含量。结果表明:最佳酶解条件为木瓜蛋白酶与风味蛋白酶体积比1∶2、酶解时间5 h、pH5.5、酶解温度45.7℃,此条件下蛋白水解度达到44.22%,与理论值误差较小。最优条件下制备的酶解液中测定出16种氨基酸,谷氨酸(63.84 g/kg)、甘氨酸(48.37 g/kg)、组氨酸(41.02 g/kg)含量较高,甲硫氨酸(0.07 g/kg)含量最低。