绿松石及其处理品与仿制品的红外吸收光谱表征

采用红外反射光谱技术,对市面上常见的充填和压制处理绿松石、仿绿松石及天然绿松石制品的红外吸收光谱进行了研究和对比。结果表明:充填处理绿松石制品的红外吸收光谱具有由聚合物中aνs(CH2)反对称伸缩振动和sν(CH2)对称伸缩振动致的吸收谱带(2 934~2 924,2 863~2 854 cm-1)及(νC O)伸缩振动所致的红外吸收特征谱带(1 739~1 718 cm-1);仿绿松石制品中则明显缺乏天然绿松石中的ν(OH)伸缩振动致红外吸收谱带(3 507,3 465 cm-1),并出现由aνs(CH2)反对称伸缩振动和sν(CH2)对称伸缩振动及(νC O)伸缩振动致红外吸收谱带以及由各自基团振动的红外吸收特征谱带(指纹区内)。依据这些特征的红外吸收光谱有助于将它们区分开。     

一种体色呈蓝色的铍扩散处理蓝宝石

针对近期市场上出现的一种体色呈蓝色或淡蓝色的Be扩散处理蓝宝石,采用EPMA,LA-ICP-MS、激光拉曼光谱仪、UV-NIS分光光度计等分析测试仪器,对50粒Be扩散处理蓝宝石样品的化学成分、拉曼光谱、UV-NIS吸收光谱特征进行了研究。测试与研究结果表明,这种Be扩散处理蓝宝石样品中,Be的质量分数最低为5.28×10-6%,最高为17.51×10-6%,平均为8.74×10-6%;其内普遍含有形态各异的斜锆石熔融或假象包裹体;由于Fe3 离子d-d电子跃迁,导致形成了样品的吸收光谱a带(377,386,451 nm)。在高温条件下,由Be扩散诱生的色心可能是导致蓝色蓝宝石呈色的主要缘由。     

中低档宝石的充填处理

以珠宝市场上充填处理海蓝宝石、碧玺等中低档宝石样品为研究对象,采用宝石显微镜与红外光谱测试技术对其充填物的宝石学特征进行了检测与分析。结果表明,蓝色闪光效应、残余扁平状气泡、充填物的流动构造及其碎渣状等宝石学特征有助于鉴别充填处理海蓝宝石和碧玉样品。位于2962,2931,2879cm^-1处、由饱和碳氢化合物v（-CH3-）与v（-CH2-）的反对称和对称伸缩振动以及位于3046cm^-1处、中等强度芳香环v（C-H）的伸缩振动致吸收谱带可有效判断充填处理海蓝宝石;位于2962,2927,2865cm^-1处、由饱和碳氢化合物v（-CH3-）与v（-CH2-）的伸缩振动致吸收带可辅助鉴别充填处理碧玺。依据充填物的颜色、形态、相对粘稠状态以及流动迹象等特征推测,不同的充填处理中低档宝石其充填物种类可能有差别。     

经多工序Be,Ti元素扩散处理的两粒蓝宝石的宝石学特征

在对22粒蓝宝石进行Be扩散检测时,意外发现2粒经Be、Ti元素扩散处理的蓝宝石。通过浸油显微观察可见宝石近底尖部位颜色在棱线处富集,这是Ti扩散处理的典型特征。激光烧蚀电感耦合等离子质谱分析发现2粒样品中Be的浓度分别为23,14ppma,由此判断两粒样品均经过了Be扩散处理。由于刚玉中Be扩散处理是在氧化氛围下进行,而Ti扩散处理在还原氛围下进行,笔者探讨了可能的处理过程。结果认为,氧化还原氛围的更换,使两种元素扩散到宝石需要多重加热,两种元素扩散处理的目的是掩盖宝石扩散处理的鉴定证据,特别是使得Be扩散处理后的常规宝石学特征缺失。作为检测机构或者流通领域而言,只要声明经"扩散处理"即可尽到明示义务,无须进行元素类型探究。     

红宝石和蓝宝石的铍扩散处理

近两年来 ,在宝石行业出现了一种在大于180 0℃的温度下同时进行了铍 (Be)的晶格扩散处理的刚玉类宝石。这一处理方法现已成为人们关注的热点。原先只能见到橙至橙桃红色的蓝宝石 ,但现在这种方法可以生产或改善出所有颜色的刚玉 ,其中包括黄色和蓝色蓝宝石以及红宝石。据 GIA的研究 ,泰国的这一新的改色过程 ,是一种在极高的温度下 ,在氧气氛中 Be向红宝石和蓝宝石的扩散。过去的 Ti扩散方法仅在表面产生一蓝色的薄层 ,而 Be扩散可以渗透得较深 ,有时可使整块宝石致色。所观察到的颜色改善 ,均为 Be在高温下的扩散所致。Be捕获空穴对 (…     

红外光谱和拉曼光谱在热处理海蓝宝石鉴定中的应用

在适当的热处理条件下,黄绿色绿柱石能够转变为理想颜色的海蓝宝石。天然海蓝宝石与热处理海蓝宝石的价格差异较大,因此探索热处理海蓝宝石的诊断性鉴定特征就显得十分必要。对不同温度下热处理海蓝宝石进行傅里叶变换红外光谱和激光拉曼光谱的测试分析,结果发现,当热处理温度超过400℃后,随着加热温度的升高,在红外光谱中由[Fe2(OH)4]2+伸缩振动引起的3 233cm-1处吸收谱峰明显减弱,直至消失。5 268cm-1附近由水伸缩和弯曲振动引起合频区的吸收带由尖峰变得宽缓;8 700,6 818cm-1两处水吸收峰的相对强度也随着加热温度升高而减弱。热处理海蓝宝石Si-O-Si伸缩振动产生的在682,3 604cm-1处的拉曼光谱谱峰强度随着加热温度升高逐渐减弱,1 070cm-1处的拉曼峰强度明显降低。经700℃加热后,拉曼光谱基线明显向上方漂移。这些光谱特征变化对热处理海蓝宝石的鉴定有重要意义。     

GE合成翡翠的宝石学特征

采用傅立叶变换红外光谱仪、激光拉曼光谱仪、电子探针、阴极发光显微镜等分析测试仪器,对美国通用电气公司(GE)合成宝石级翡翠的化学成分、振动光谱、吸收光谱及阴极发光等特征进行了研究。结果表明,GE合成翡翠的主要化学成分为w(SiO2)=59.74%~61.72%,w(Al2O3)=23.90%~24.97%,w(Na2O)=13.65%~14.85%以及微量的w(Cr2O3)=0.05%~0.07%,w(K2O)=0.02%~0.04%,w(CaO)=0.02%~0.06%。在3 400~3 700 cm-1范围内,GE合成翡翠显示一组(3 373,3 471,3 614 cm-1)与天然翡翠截然不同的且由羟基伸缩振动所致的红外吸收谱带。在376,700,989,1 039 cm-1处出现的拉曼锐谱峰与天然翡翠的拉曼光谱特征基本相同,表征GE合成翡翠具典型的硅氧四面体链状结构,且结晶程度较高。GE合成翡翠主要由Cr3 致色,在可见光区域内,由其4A2→4T2和4A2→4T1能级间跃迁而产生630,445 nm的吸收。     

天然与合成紫晶的3 543 cm-1红外吸收谱带及其鉴定价值

重点对3 800～3 000 cm-1范围的红外吸收光谱在鉴别天然与合成紫晶中的适用性和局限性进行了研究.3 680, 3 664, 3 630 cm-1处吸收带的存在可以确认紫晶为人工合成的, 但仅指那些在近中性NH4F溶液中合成的紫晶.相反, 商业上大量的合成紫晶是在碱性K2CO3溶液中合成的, 这些紫晶的红外吸收光谱并无明显的鉴定特征.前人的研究发现了在近3 595, 3 543 cm-1处吸收带的潜在鉴定价值.3 595 cm-1吸收带在合成紫晶的红外吸收光谱中并未出现, 在一些天然紫晶中也常常缺失.3 543 cm-1吸收带出现在绝大多数碱性溶液中合成紫晶的红外吸收光谱中, 但有时也在天然紫晶中出现.因此, 它只是鉴别合成紫晶的临时性证据.3 543 cm-1吸收带在有些类型的合成紫晶中缺失.要准确地鉴定天然与合成紫晶一定要根据其红外光谱、内部生长结构(包括双晶)和包裹体特征综合判断.     

含铅元素的铍扩散处理红宝石、蓝宝石的特征研究

铍扩散处理和铅玻璃充填处理是目前红宝石和蓝宝石常见的处理方式,但刚玉宝石中同时出现铍元素和铅元素极为少见。其特征对铍扩散处理过程带入异常铅元素的红宝石和蓝宝石的实验室鉴定具有重要意义。本文利用常规宝石学仪器、超景深显微放大观察、荧光图像测试、红外光谱测试、X射线荧光光谱(XRF)、激光诱导击穿光谱(LIBS)、紫外一可见分光光度计等测试手段,研究结果显示两粒样品矿物包体存在超高温迹象,且颜色异常富集是该类铍扩散处理的佐证;化学成分分析中高强度的铍元素和异常铅元素,同时指示经过Be扩散处理,异常Pb元素未体现经过铅玻璃充填处理放大特征;紫外一可见分光测试显示样品具有由Fe、Ti、Cr等过渡金属元素产生的374 nm、387 nm、450 nm、555 nm、693 nm的吸收。     

蓝宝石的紫外-可见光谱及其致色机理分析

蓝宝石的紫外-可见吸收光谱和能谱分析结果表明, 蓝宝石从粉红色→紫色→蓝色→绿色→黄绿色→黄色, 其Fe3 的浓度相对Fe2 -Ti4 离子对浓度由低至高变化; 浅蓝色到深蓝色蓝宝石中的Fe和Ti均有所增加; 褐色蓝宝石含有相对较多的Fe和Cr; Mn可能与蓝宝石的紫色有成因联系. 热处理蓝色蓝宝石和辐照黄色蓝宝石在450, 375, 387 nm处的吸收较未处理的弱, 辐照黄色蓝宝石在405 nm处有吸收带.     

蓝宝石中Fe2+和Ti4+离子的扩散系数及其对扩散处理工艺的影响

论述蓝宝石中Fe^2 和Ti^4 离子的扩散系数及其对扩散处理改色工艺的影响。根据实测泰国扩散处理蓝宝石样品的扩散层厚度和处理工艺条件，计算了Fe^2 和Ti^4 致色离子在蓝宝石中的扩散系数。实验表明，致色离子扩散系数对蓝宝石扩散处理改色工艺的制定具有重要的指导意义。     

多级误差扩散加网技术研究

为了提高输出图像的质量,使人眼视觉产生连续调效果,使用了多级误差扩散算法生成网目调图像。多级加网技术在传统二值（0和1）之间增加了中间阶调,突破了长久以来人们一贯应用的＂非黑即白＂输出理念。通过分析传统误差扩散和多级误差扩散理论基础,提出了多级多阶误差扩散算法。多级多阶误差扩散采用迭代算法,引用图像四叉树来表示原始图像与输出网目调图像的差异。算法结果表明,多级多阶误差扩散加网技术使加网后的图像具有更为精确的阶调复制和更为丰富的层次再现,图像之间的过渡更为平整自然。     

Physical changes in white and brown rice during simulated gastric digestion

Previous studies have shown that brown rice generates lower glycemic responses than white rice, a trait that may be beneficial in the dietary management of chronic diseases such as diabetes and hyperlipidemia. The objective of this study was to investigate influence of rice digestion on the physical properties of the gastric digesta that may further impact intestinal absorption. A dynamic stomach model, human gastric simulator, was used to simulate the gastric digestion of white and brown rice. The pH, solids content, and rheological properties of the gastric digesta, as well as the size distribution of particles were studied. Static soaking was conducted to reveal the changes in moisture absorption and texture in rice kernels during simulated gastric digestion, as affected by shaking and the acid in gastric juice. Magnetic resonance imaging (MRI) was used to image the diffusion of gastric juice into the rice kernels. The results indicate that the bran layer on brown rice had a profound effect in digestion, as it inhibited the absorption of moisture and acid leading to decreased texture degradation, thus delaying the rice disintegration as well as dissolution and slowing emptying of solids. MRI is effective in exhibiting the diffusion of gastric juice as affected by gastric acid and the influence of bran. This study provided quantitative evidence regarding the manner in which structural differences between white and brown rice affect their gastric digestion. PRACTICAL APPLICATION: The study presented in this paper focuses on how the structural differences in white and brown rice affect their gastric digestion. This information may help consumers to better understand the health benefits associated with eating brown rice.     

二氧化碳浸渍处理对生姜真空微波干燥特性及微观结构的影响

为探究二氧化碳浸渍处理对生姜真空微波干燥特性及微观结构的影响,分别选用不同浸渍温度(35、40、45℃)、压力(1、2、3 MPa)、时间(3、5、7 h)对生姜进行预处理,测定干燥过程中水分比、干燥速率、有效扩散系数的变化,并进行薄层干燥模型拟合。此外,对不同浸渍条件下生姜的微观结构进行研究。试验结果显示:经二氧化碳浸渍后,生姜的干燥速率显著提高,尤其在干燥后期。当浸渍条件为2 MPa、45℃、7h时,样品的水分扩散最快,且干燥时间相比于直接干燥样品缩短了47%。5种薄层干燥模型中,通过比较决定系数(R2)、卡方(χ2)和均方根差(RMSE),认为Modified Page模型对生姜干燥过程中水分变化的拟合效果最好。扫描电镜结果显示,二氧化碳浸渍增大了生姜内部的细胞面积,增加孔隙率,提高物料的传质传热性能。结果表明,二氧化碳浸渍对于改善生姜内部结构、提高干燥效率具有积极的影响,为生姜干燥新技术的开发提供了理论依据。     

Effect of cocoa butter structure on oil migration

Oil migration from a high oil content filling into adjacent chocolate causes changes in product quality. The objective of this study was to quantify the oil migration from a cream filling system into cocoa butter, which provided a model for the behavior of chocolate-enrobed confectionery products with a soft, creamy center. Magnetic resonance imaging (MRI) was used to monitor spatial and temporal changes of liquid lipid content. A multislice spin echo pulse sequence was used to acquire images with a 7.8 ms echo time and a 200 ms repetition time using a 1.03 T Aspect Imaging MRI spectrometer. Samples were prepared as a 2-layer model system of cocoa butter and model cream filling. Three methods were used to prepare the cocoa butter: static, seeded, and sheared. Samples were stored at 25 °C for a time frame of 56 d. The rate of oil migration was quantified by a kinetic expression based on the linear dependence of oil uptake by cocoa butter and the square root of the time. Samples showed distinctly different rates of oil migration, as evidenced by quantitative differences in the kinetic rate constant. Practical Application: This work will be helpful to elucidate the influence of crystallization process and structural properties such as crystal nanostructure and crystal habit on the migration of oil through a crystalline fat matrix.     

A mathematical model to describe flavour release from gelatine gels

A theory of flavour release from gelatine-sucrose gels has been developed based on combined interfacial mass and heat transport. The driving force for flavour release is shown to depend on the bulk melting temperature of the gel, which depends on the gelatine and sucrose concentrations. For gels possessing melting points below the mouth temperature, the driving force for flavour release is the rate at which heat can diffuse into the gels matrix and initiate melting. For harder gels with melting points above mouth temperature the diffusion of sucrose from the surface of the gel into the adjacent saliva phase is the rate limiting step for flavour release, because this lowers the melting temperature of the surface layer. The theoretical model gives good agreement with in vitro release experiments using gelatine gels containing sucrose and dye.     

Probe diffusion in κ-carrageenan gels determined by fluorescence recovery after photobleaching

The effects of free volume and heterogeneity on probe diffusion in κ-carrageenan gels were determined by fluorescence recovery after photobleaching (FRAP) and rheology. By changing the ionic conditions, biopolymer concentration and end temperature, different microstructures and aggregation kinetics in the κ-carrageenan gels were evaluated. The results of the FRAP measurements were compared to transmission electron microscopy (TEM) and nuclear magnetic resonance diffusometry (NMRd) data from previous studies. The results showed that the free diffusion rates of the probe (FITC dextran) in water were influenced by both temperature and ionic conditions. The free diffusion values were used for normalization of the diffusion rates in the κ-carrageenan gel measurements. The compatibility between FITC dextran with different molecular weights (10 and 500 kDa) and κ-carrageenan was evaluated. The results showed that the larger FITC dextran probe phase separates; therefore only the 10 kDa FITC dextran probe was used in the FRAP experiments. FRAP measurements and NMRd probe diffusion in combination with TEM in κ-carrageenan revealed that the void space, degree of aggregation and heterogeneity influence the probe diffusion rate. The κ-carrageenan gelation was analyzed at different end temperatures using rheology and FRAP. The FITC dextran probe diffusion was not influenced by κ-carrageenan aggregation, regardless of rheological gelation kinetics and storage modulus near the gel point. This indicates that the average void space between the gel strands is larger than the size of the probe. Good correlation between the microstructure and the probe diffusion rate in κ-carrageenan gel with different ionic conditions and constant biopolymer concentration were obtained with TEM and FRAP.     

Sorption of ethyl acetate and d‐limonene in poly(lactide) polymers

Poly(lactide) (PLA) polymers have garnered increased attention in the last few years as food packaging materials because they are environmentally friendly polymers. As the production of PLA increases and price per pound drops, PLA is becoming a growing alternative as a green food packaging material. In this research, the organic vapor barrier properties of commercially available PLA polymers were studied. Gravimetric sorption tests in PLA films were carried out, and the diffusion (D), solubility (S) and permeability (P) coefficients for ethyl acetate and d‐limonene in PLA were determined. For ethyl acetate, values of P = 1.22 × 10^?17 kg m m^?2 s^?1 Pa^?1, D = 2.63 × 10^?15 m² s^?1, and S = 4.62 × 10^?3 kg m^?3 Pa^?1) at 45 °C and a partial pressure of 12 654 Pa were obtained. For d‐limonene, no trace was detected after 21 days of testing at 45 °C and 258 Pa, which indicates a permeability coefficient lower than 9.96 × 10^?21 kg m m^?2 s^?1 Pa^?1. Poly(lactide) polymers demonstrated good aroma barrier to ethyl acetate and d‐limonene, and will most likely be good aroma barriers. PLA is not likely to promote flavor loss by either permeation or scalping. Copyright © 2005 Society of Chemical Industry     

干制温度和切片厚度对山楂切片热风干制动力学的影响

在本研究中,为了探讨热风温度和切片厚度对山楂热风干制动力学的影响,将厚度为2 mm和4 mm的山楂切片置于50⁹0℃的热风干燥箱内进行干制处理,并采用5种常见食品薄层干燥模型对实验数据进行非线性拟合,通过比较评价决定系数（R²）、卡方（χ²）和均方根误差（RMSE）等统计数据确定山楂切片薄层热风干燥过程的最优模型。结果表明:山楂切片薄层热风干燥是内部水分扩散控制的降速干燥过程。Page模型是描述山楂切片薄层热风干燥过程的最优模型。不同干燥条件下有效水分扩散系数Deff和活化能Ea的求解结果表明,有效水分扩散系数Deff随热风温度和切片厚度的增加而增加,在干制温度范围内有效扩散系数的值在2.69×10^-1116.12×10^-11m²/s之间变化。对于切片厚度为2 mm和4 mm的山楂切片,活化能Ea分别为20.43、26.25 k J/mol。      

Evolution of Moisture Distribution During Storage in a Composite Food Modelling and Simulation

In order to predict moisture transfer in a composite food, a mathematical model was developed and tested on a 2‐components system constituted of a sponge‐cake in contact with a fresh wet filling. Using independent sorption kinetic experiment, a power law was found as representative of the effect of moisture content on water effective diffusivity of sponge‐cake. The parameters of power law was then adjusted using the model optimization procedure on moisture profiles measurements of sponge‐cake in contact with a 0.99 water activity agar gel at 20°C. The model was validated with 0.95 and 0.90 water activity agar gels and successfully used to predict moisture transfer in a real food (processed cheese/sponge‐cake system).