Synthesis and 13C-NMR Spectroscopy of Methylated beta-Cyclodextrins

The methylated analogues of ß-cyclodextrin dissolve in cold water 10 – 20 times better than ß-cyclodextrin itself, however, quite unusually on heating they crystallize from the solution. The structure of heptakis-(2,6-di-O-methyl)- and heptakis-(2,3,6-tri-O-methyl)-ß-cyclodextrin was proved by gas-liquid chromatographic and ¹H-NMR and ¹³C-NMR spectroscopic investigations. The corresponding model compounds were synthetized and, according to ¹³C-NMR spectroscopic investigations, a part of the so far published NMR assignations have to be corrected.     

13C-NMR分析漆酶处理木素的结构特征

利用13C-NMR技术对漆酶、漆酶/介体体系处理前后枫香木酶解木素进行结构分析.结果表明,经漆酶/介体体系(LMS)处理后,木素的部分β-O-4结构发生醚键断裂,脱甲基或脱甲氧基反应发生,根据结构变化推断反应过程中紫丁香基型结构优先反应;经漆酶处理后,木素单位苯环的羰基含量和甲氧基含量增加.     

Saccharides of Developing Wheat Grain Determined by 13C-NMR Spectroscopy

Automated carbon-13 nuclear magnetic resonance spectroscopy of saccharides from wheat serially harvested through one growing season showed variation of glucose, fructose, sucrose and maltose similar to previous analyses. In a diurnal series glucose and fructose concentrations fluctuated periodically but were relatively unaffected by light and dark. Qualitative ¹³C-NMR showed myo-inositol, glycerol, 1-kestose, 6-kestose, and glucofructans with glucose: fructose ratios up to 1:12. With increasing chain length there were increasing proportions of 6–2 over 1–2 linkages. Sugars previously reported but not found here included xylose, arabinose, mannose, galactose, raffinose, fructosyl raffinose, stachyose, melecitose and maltotriose.     

固体核磁CP/MAS 13C-NMR在植物纤维原料研究中的应用

固体核磁CP/MAS 13C-NMR光谱已经成为一种重要的科学研究方法,本文综述了在植物纤维和制浆造纸科学研究方面的应用.     

A 13C-NMR study of lipid alterations during fish canning: Effect of filling medium

Carbon-13 nuclear magnetic resonance spectroscopy was applied to study the effect of the filling medium on lipid modifications occurring during the industrial canning of tuna (Thunnus alalunga). In the two media studied—brine and soybean oil—increases in the free fatty acid level were observed with preferential hydrolysis of polyunsaturated fatty acids esterified in the sn-2 position of the glycerol moiety. The extent and mechanism of lipolysis seem to be independent of the filling medium used. Quantitative results obtained for the main lipid classes showed dilution of the natural lipids of muscle by triacylglycerols from the filling medium in oil-filled cans.     

Gum arabic (Acacia senegal): unambiguous identification by 13C-NMR spectroscopy as an adjunct to the Revised JECFA Specification, and the application of 13C-NMR spectra for regulatory/legislative purposes.

The JECFA Specification for gum arabic was revised in 1990 to reflect more closely the specification of the Test Article used in evaluations that led to its classification 'ADI not specified' in 1982/83. Some producers and traders have objected to the Revised Specification; in contrast, consumer-protection groups consider that it remains too lax to provide the degree of safety assurance expected. This paper presents analytical data that confirm the mean values previously established for nitrogen and the specific rotation of bulk commercial gum arabic from Acacia senegal. The data also establish that natural gum arabic imported into the USA and Europe in 1989/91 met the Revised Specification, but that a disturbingly high proportion of spray-dried, processed gums sold as 'gum arabic' did not. NMR spectroscopy has (a) indicated that some such samples are based on non-permitted gums and (b) confirmed that the 1983 Test Article represents not only typical 1990/91 shipments but also a wide range of reference gum arabic samples from other reputable sources. Details of a representative 13C-NMR spectrum, derived by averaging the relative intensities for the characteristic resonances of 35 gum arabic samples, are given for future regulatory/legislative purposes. Some limitations of the Revised Specification and its susceptibility to commercial exploitation are discussed.     

Milk identification of different species: 13C-NMR spectroscopy of triacylglycerols from cows and buffaloes' milks

Triacylglycerols from cows and buffaloes' milk fat were investigated by 13C nuclear magnetic resonance (NMR) spectroscopy. By the addition of pure triacylglycerols standards, we identified the resonances of both milk fats, and the peaks were used for qualitative and quantitative analysis of acyl groups. Multivariate analysis treatment of triacylglycerols distribution and composition parameters enabled us to identify milk. This study shows that NMR can safely be used to quantitate milk fatty acid content, providing unique information for milk identification of different animal species.     

甘氨酸及其小肽铜配合物的可见光谱

利用可见光谱研究了甘氨酸及其二、三肽与铜元素的配位作用 .结果表明 ,氨基酸和二、三肽的配合行为不同 ,而小肽之间配合行为基本相似 .由于晶体场稳定化能效应 (CFSE)的存在 ,配位比对小肽铜配合物的结构和配合程度影响不大 ,一般趋向于 1∶1配位 .pH值对配合反应影响较大 ,以 pH值为 9最佳 .     

核磁共振碳谱测定天然鱼油和加工鱼油中多不饱和脂肪酸的位置分布

鱼油是n-3多不饱和脂肪酸的重要来源,为明确鱼油中多不饱和脂肪酸的位置分布,采用气相色谱法测定了4种天然鱼油和3种加工鱼油的总脂肪酸组成,并采用核磁共振碳谱(¹³C-NMR)分析其多不饱和脂肪酸的位置分布,同时运用Novozym 435醇解结合气相色谱分析了4种天然鱼油中甘油三酯上饱和脂肪酸(SFA)和单不饱和脂肪酸(MUFA)的位置分布。结果表明：加工鱼油中二十二碳六烯酸(DHA)含量为28.43%～76.63%,二十碳五烯酸(EPA)含量为12.72%～56.37%,总体含量均高于天然鱼油;天然鱼油中DHA主要分布在sn-2位,sn-2 DHA相对含量为50.39%～63.71%,而加工鱼油中DHA则处于随机分布状态,sn-2 DHA相对含量为28.78%～36.76%;不同天然鱼油中SFA和MUFA没有明确分布规律。综上,鱼油的加工工艺可以提高DHA的含量但是改变了其在甘油三酯碳骨架的分布。     

Alkaline Degradation of Monosaccharides Part VIII. A13C NMR Spectroscopic Study

The analysis of alkaline degradation products of monosaccharides has been performed by ¹³C NMR spectroscopy. The ¹³C chemical shifts of several carboxylic acids produced by alkaline degradation of monosaccharides have been determined. The application of these data to the identification and quantification of products in an alkaline degradation mixture of D -glucose is presented. Carboxylic acid products up to 6 carbon atoms have easily been identified in such complex reaction mixtures. Furthermore, information on the different functional groups present in the oligomeric reaction products has been obtained from the alkaline degradation of 1-¹³C-D -glucose.     

Emerging Spectroscopic and Spectral Imaging Techniques for the Rapid Detection of Microorganisms: An Overview

Microorganism contamination and foodborne disease outbreaks are of public concern worldwide. As such, the food industry requires rapid and nondestructive methods to detect microorganisms and to control food quality. However, conventional methods such as culture and colony counting, polymerase chain reaction, and immunoassay approaches are laborious, time‐consuming and require trained personnel. Therefore, the emergence of rapid analytical methods is essential. This review introduces 6 spectroscopic and spectral imaging techniques that apply infrared spectroscopy, surface‐enhanced Raman spectroscopy, terahertz time‐domain spectroscopy, laser‐induced breakdown spectroscopy, hyperspectral imaging, and multispectral imaging for microorganism detection. Recent advances of these technologies from 2011 to 2017 are outlined. Challenges in the application of these technologies for microorganism detection in food matrices are addressed. These emerging spectroscopic and spectral imaging techniques have the potential to provide rapid and nondestructive detection of microorganisms. They should also provide complementary information to enhance the performance of conventional methods to prevent disease outbreaks and food safety problems.     

光谱预处理结合模拟退火算法的小麦粉面筋含量检测

为得到可靠的小麦粉中面筋含量定量分析模型,基于光谱预处理及模拟退火算法（simulated annealing algorithm,SAA）对近红外光谱（near infrared spectroscopy,NIR）进行优化处理。偏最小二乘（partial least squares,PLS）回归用于建立预测模型,以决定系数R2、校正均方根误差（root mean square error of calibration,RMSEC）、预测均方根误差（root mean square error of prediction,RMSEP）为指标,对比在不同光谱预处理条件下建立的回归模型与光谱预处理结合模拟退火算法优化处理条件下的回归模型。结果表明光谱预处理结合SAA-PLS模型能够有效提高模型的稳定性和预测能力,将R2从0.763?7提高到0.949?1、RMSEC从1.371?2降低到0.589?8、RMSEP从1.450?2降低到0.534?1。结果说明,光谱预处理结合模拟退火算法对光谱进行优化处理是可行的,模型预测能力和稳定性均优于未处理模型和仅进行光谱预处理的模型。     

Rapid Near Infrared Spectroscopic Method for the Detection of Spoilage in Rainbow Trout (Oncorhynchus mykiss) Fillet

The possibility of using visible and short‐wavelength near‐infrared (SW‐NIR: 600 to 1100 nm) spectroscopy to detect the onset of spoilage and to quantify microbial loads in rainbow trout (Oncorhynchus mykiss) was investigated. Spectra were acquired on the skin and flesh side of intact trout fillet portions and on minced trout muscle samples stored at 4 °C for up to 8 d or at room temperature (21 °C) for 24 h. Principal component analysis (PCA) and partial least squares (PLS) chemometric models were developed to predict the onset and degree of spoilage. PCA results showed clear segregation between the control (day 1) and the samples held 4 d or longer at 4 °C. Clear segregation was observed for samples stored 10 h or longer at 21 °C compared with the control (0 h), indicating that onset of spoilage could be detected with this method. Quantitative PLS prediction models for microbial loads were established. For trout fillets, 4 °C: R= 0.97, standard error of prediction (SEP) = 0.38 log colony‐forming units (CFU)/g (flesh side); R= 0.94, SEP = 0.53 log CFU/g (skin side); R= 0.82, SEP = 0.82 log CFU/g for minced fish held at 21 °C. These results indicate that SW‐NIR in combination with multivariate statistical methods can be used to detect and monitor the spoilage process in rainbow trout and quantify microbial loads rapidly and accurately.     

基于模拟退火算法优化波长的面粉品质检测

模拟退火算法（simulated annealing algorithm,SAA）是一种随机搜索、全局优化算法,为提高近红外光谱检测面粉品质模型的准确度与稳健性,实验提出基于SAA优化波长,再结合偏最小二乘（partial least squares,PLS）法建模预测的定量模型,并对SAA中冷却进度表参数设置进行对比分析。实验依据面粉中灰分含量梯度,随机选取126 份样本的近红外光谱建立SAA-PLS模型。结果发现,SAA从2 074 个波数优选出70 个波数,结合PLS建立的定量模型相关系数为0.976 0,交互验证均方根误差（root mean square error of cross validation,RMSECV）为0.022,预测均方根误差（root mean square error of prediction,RMSEP）为0.030 1,全谱建立的PLS模型相关系数为0.778 5,RMSECV为0.066 6,RMSEP为0.076 8。结果表明,基于SAA优化特征谱区,建立灰分定量模型是可行的,且准确度与稳健性明显优于全谱定量分析模型。     

Solid State 13C NMR and Diffuse Reflectance Mid-Infrared Spectroscopic Analysis of the Effects of Retting on the Chemical Composition of KenafFibre

Bast ribbons from Tainung 1 (T₁) and Guatemala 45 (G₄₅) cultivars of kenaf ( Hibiscus cannabinus ) were subjected to a chemical retting process. The resulting changes at the base and tip regions of each cultivar were analysed using solid-state ¹³C NMR and diffuse reflectance mid-infrared spectroscopies. Chemical retting was performed by boiling the substrates in NaOH (70 g litre⁻¹) +NaHSO₃ (5 g litre⁻¹) for 1 h, after which they were neutralised, washed and air dried. This process produced large decreases in the non-cellulosic components, though 25% of the phenolic component was left undegraded, and cellulose crystallinity was increased by ∽5% over that in unretted samples.     

基于CRISPR-Cas13的单增李斯特菌RNA快速检测方法的建立

为实现食品中单增李斯特菌污染的快速检测,本研究构建了一种基于CRISPR-Cas系统和Broccoli适配体的RNA均相检测技术。利用Cas 13与cr RNA锚定序列结合形成识别元件cr RNA-Cas13复合物,靶标RNA存在时可激活Cas 13的非特异性RNase活性,并利用点亮型RNA适配体Broccoli作为信号探针,监测cr RNA此-Cas13的活化状态。荧光值的变化与单增李斯特菌浓度存在线性关系,利用来检测单增李斯特菌。本研究所构建的检测可在30min内完成对于单增李斯特菌的的识别与检测,检出限为148CFU/m L,对细菌具有良好的检测特异性,可区分大肠杆菌、鼠伤寒沙门氏菌和蜡样芽孢杆菌。在牛奶模型中单增李斯特菌的加标回收率为95.15%～97.99%。该方法具有较好的灵敏度、特异性,可直接靶向检测致病菌RNA,无需逆转录、PCR扩增和核酸标记,简化了实验流程,对于实现食品中单增李斯特菌的现场检测及生物安全控制具有重要意义。     

顽火辉石的定向光谱学测试

在加工单晶宝石的过程中,晶体定向有着非常重要的作用。傅里叶变换红外光谱和激光拉曼光谱定向测试宝石虽然得到的结果不一定准确,但是可以作为辅助证据对传统结晶学定向进行验证。通过对顽火辉石样品的切片进行定向的红外光谱、激光拉曼光谱测试与对比分析,探讨了利用红外光谱、拉曼光谱进行晶体定向的可能性,获得了可以利用红外光谱的水峰在3 400~3 600cm~(-1)范围内的形状、强度及位置、拉曼光谱中的1 009~1 020cm~(-1)处拉曼峰形态、强度总体峰数量、荧光背景等要素对顽火辉石晶体进行初步定向的认识。     

高温高压处理钻石的谱学特征综述

综述了近年来高温高压处理钻石的成果。该处理方法的对象主要有天然钻石、高温高压合成钻石以及化学气相沉淀法合成钻石。系统地总结和分析了该类处理钻石的谱学特征,包括紫外-可见光吸收光谱、红外吸收光谱、拉曼光谱、光致发光光谱及荧光特征,提供了其主要的鉴定依据。     

Detection of the illicit extension of potable spirituous liquors using 13C: 12C ratios

The stable carbon isotope ratios of 122 samples of common liquors and nine ferment able substrates have been determined. The δ¹³C values of the liquors analysed reflected those in the plant from which the fermentable substrate was derived. These values ranged from —23.4 to– -26.0% relative to Pee Dee Belemnite (PDB) for substrates derived from C₃ plants while those from C₄ plants ranged from —10.3 to —11.8% PDB. The application of this technique to detect the illicit extension of whisky has been investigated. As little as 2.9% grape spirit or 5.7% molasses spirit can be detected in whisky although the lower limit is dependent on the δ¹³C value of both the authentic whisky and the diluent. Measurement of ¹³C: ¹²C ratios could also be used to check that imported brandies conform with local requirements.