Application of a hybrid variable selection method for the classification of rapeseed oils based on 1H NMR spectral analysis

¹H nuclear magnetic resonance (NMR) spectroscopy was utilized to distinguish the brands of rapeseed oils. As there are more than four hundreds of NMR variables which can cause the discrimination model redundancy, it is necessary to do effective variable selection. Successive projections algorithm (SPA) executed on the full spectrum only improved a few correct answer rate (CAR) and Cohen’s kappa coefficient (K) compared to full spectrum-least-square support vector machine (LS-SVM) model. The better results of uninformative variable elimination (UVE)-based SPA calculation show that it is necessary to do UVE before SPA. Because the cutoff threshold selection in UVE algorithm using an artificial random noise cannot obtain the optimal results, we applied simulated annealing (SA) algorithm to estimate the optimal cutoff threshold. The discrimination results show that UVE-SA did better works than conventional UVE. Only 13 variables were obtained by UVE-SA-SPA while the conventional UVE-based SPA selected 77 variables. The best 97.5% CAR and K of 0.967 result of UVE-SPA-LS-SVM model show that it is feasible to distinguish different brands of rapeseed oils using ¹H NMR spectra. It shows that a combination of SA, UVE, and SPA is effective method for the classification of rapeseed oils. Final result shows that all acyl chains, linolenyl and linoleyl chains, and triglycerides were most important for the classification.     

A rapid method to evaluate the chocolate smoothness based on the tribological measurement

Cocoa is the primary ingredient in chocolate, and cocoa concentration attributes to the smoothness of the chocolate. Supporting this statement, we assessed the smoothness and melting properties of five chocolates of different cocoa concentration from three brands using the professional sensor evaluation and weight method, respectively. Artificial saliva was added to obtain the mixed chocolate solutions, and their viscosity and coefficient of friction (CoF) were measured for three rubbing pairs. The correlation of chocolate smoothness with their viscosities and average CoF (aCoF) was also discussed. The results indicated that the cocoa concentration significantly affected the smoothness of the chocolates among the three brands. The mixed solution of 50% chocolate could be a representative of oral processing, but their viscosities were not proficient enough to effectively characterize their smoothness. The aCoF of 50% chocolate solution could be rapid and effective to evaluate their smoothness. In addition, the Two-GCTPE rubbing pair was more suitable way to evaluate the smoothness of similar foods in the oral environment. The study results will provide a better insight into characterizing certain attribution of similar foods.     

1H NMR approach as an alternative to the classical p-anisidine value method

Aldehydes, formed as secondary oxidation products during the autoxidation process of oils and fats, are analytical markers used to assess the lipid deterioration status. Generally, the level of aldehydes is expressed as the p-anisidine value (AV). This deterioration index is based on the reaction of the carbonyl group with p-anisidine leading to the formation of an intensively coloured Schiff base which is determined spectroscopically (UV/ViS). ¹H NMR provides an alternative approach by enabling the quantification of individual aldehydes like n-alkanals, 2-alkenals or (E,E)-2,4-alkadienals. This work illustrates that the AV can be modelled as a linear combination of the NMR integrals of aldehydes. A functional relationship was derived on the basis of calibration experiments. The suitability of the model is shown by comparing the NMR-determined AVs with the classical AVs of 79 commercially available edible oils of different oil types.     

一种基于点云数据的复杂地形CFD网格生成方法

针对CFD网格生成中地形数据精确度不高的问题,提出一种基于点云数据的复杂地形CFD网格生成方法.该方法引入七参数求解方法生成地方坐标点云文件,采用点—线—面—体方式生成地形网格,并基于多面体网格转换方法进行网格优化.实例验证结果表明,生成的地形网格与实际地形吻合度高、数据精确度高,适合用于后期的CFD精细模拟应用.     

Application of chemometrics to low-field 1H NMR relaxation data of intact fish flesh

The possibilities for application of low-field ¹H nuclear magnetic resonance (NMR) as a rapid method for simultaneous assessment of basic quality parameters in fish were explored. In a first experiment, 200 salmon (Salmo salar) samples mapping the variation over an entire fish were measured by NMR and subsequently analysed for oil or water content by standard chemical methods. In a second experiment, 58 differently thawed cod (Gadus morhua) samples were measured by NMR and subsequently analysed for water-holding capacity. Correlations between chemical data and NMR data were evaluated using partial least squares (PLS) regression on complete relaxation curves and compared with conventional regression models on exponential fitting parameters. Predictions on an independent test set were superior for the PLS regression models, with optimal prediction errors of 12 g kg⁻¹, 6 g kg⁻¹ and 3.9% for oil and water content in fresh salmon flesh and water-holding capacity in thawed cod flesh respectively. Thus rapid, non-invasive low-field NMR can be used to simultaneously determine both oil and water content of fish flesh. Furthermore, it can predict water-holding capacity of cod flesh, with an R² of 0.9 over the range 30–90%, as determined by a centrifuge test. © 1999 Society of Chemical Industry     

Metabolite release and protein hydrolysis during the in vitro digestion of cooked sea bass fillets. A study by 1H NMR

Proton Nuclear Magnetic Resonance (¹H NMR) was used to study micro-wave cooked European sea bass (Dicentrarchus labrax) fillets, along five different points of their in vitro digestion: after oral digestion, after gastric digestion and subsequent increasing of the pH to 5.0, and after 90 and 180 min of duodenal digestion. During the gastric phase, the appearance of broad signals in different spectral regions, typical of amino acid protons, provided evidence for the expected release of unstructured fragments of denatured proteins, whilst smaller peptides, with sharper signals in the same spectral regions, were becoming visible only after duodenal digestion. Prior digestion, the spectral features of trichloroacetic acid extracts, from raw and cooked fish fillets, have been analysed to assess whether a significant protein hydrolysis or metabolite release (e.g., amino acids, organic acids, saccharides, and nucleotide derivatives) already occurred during cooking, by comparing the spectral profiles of these extracts. No significant differences among the molecular profile of both extracts were found. The present study demonstrates the suitability of NMR spectroscopy to follow the kinetics of fish fillets digestion under in vitro conditions simulating human digestion.     

1H NMR characterisation of the lipid fraction and the metabolite profiles of Fossa (pit) cheese

Fossa cheese is a typical Italian cheese characterised by ripening in pits dug in tuffaceous rock. In this work, ¹H NMR spectroscopy was applied to characterise the lipid fraction and the metabolite profile of Fossa cheese produced with sheep's milk. Samples were collected before and after ripening in different pit environments. The higher levels of free amino acids (FAAs) found in samples suggest that cheeses underwent a strong proteolytic process. Differences in quantity and variety of FAAs were influenced by the two ripening environments. Diacylglycerols and butyric acid, which can be linked to lipolysis, were detected in all the samples. Longer ripened samples had higher contents of rumenic acid (18:2 cis-9, trans-11) and glycerol, and lower contents of lactate and citrate. The presence of tyramine was observed by two-dimensional NMR, while cadaverine was not detected in the samples.     

基于非目标~1H NMR指纹图谱技术验证中国葡萄酒原产地

为了探讨非目标指纹图谱技术验证中国葡萄酒原产地的可行性,采用一维核磁共振氢谱(1H NMR)技术,对沙城、昌黎和昌吉三大特色原产地葡萄酒的224个样品进行分析。结果表明,主成分分析(principal component analysis,PCA)结合线性判别分析(linear discriminant analysis,LDA)建立的留一交叉验证模型,实现对沙城、昌黎和昌吉葡萄酒原产地样品准确识别率为92%,73%和68%;为避免PCA/LDA模型出现过拟合现象,采用外部重复双随机交叉验证方法对PCA/LDA模型的有效性进行验证。葡萄酒1H NMR指纹图谱包含葡萄酒原产地特征信息,通过多变量统计分析可以构建非目标1H NMR指纹图谱的中国葡萄酒产地验证技术模型。     

基于多源光谱特征融合技术的花生油掺伪检测

以拉曼、近红外2种光谱特征融合结合化学计量学方法对花生油掺伪进行了定量分析。分别用激光拉曼、激光近红外光谱仪采集134个掺伪油样本的光谱数据,采用SPXY算法对样本集进行划分。拉曼光谱(Ram)和近红外光谱(near infrared spectroscopy,NIR)数据进行预处理后,采用后向间隔偏最小二乘法(BiPLS)和联合间隔偏最小二乘法(synergy interval partial least squares,Si PLS)分别提取2种光谱的特征波长;将提取的特征波长融合,结合支持向量机回归(SVR)建立数学模型,采用网格搜索算法(CV)对SVR模型的参数组合(C,g)值寻优,建立最优参数模型。研究表明:建立的Ram-NIR-SVR模型能够实现花生油中掺杂油脂含量的快速准确预测,预测集和校正集的相关系数R分别达到0.98和0.99,均方根误差(MSE)低于2.38E-3;对比不同特征波长提取方法,并与单光谱分析技术比较,可以看出,数据融合技术能够增强模型预测能力,减小模型参数,有利于模型的实际应用,体现了2种光谱很好的互补性。表明光谱分析结合数据融合技术对食用油真实性综合鉴别具有重要意义。     

Statistical method to evaluate the occurrence of PCB transformations in river sediments with application to Hudson River data

Polychlorinated biphenyls (PCBs) were produced in the mid 1900s for industrial use. The term PCBs refers to 209 theoretically possible chlorinated compounds of the biphenyl molecule (congeners). The number and location of the chlorines govern both the environmental fate and toxicity of each congener. Changes in the distribution of congeners in river sediments can result from congener transformation and/or preferential congener transport. This study exploits the distribution of PCB congeners, specifically congeners that maintain a constant ratio relationship in the commercially manufactured PCB mixtures (Aroclors), to quantify the likelihood of congener distribution shifts in river sediment. By using relative abundances, the influence of total PCB bias is eliminated. Correlated congeners (tracker pairs) maintain a constant relative proportion in sequentially more-highly chlorinated Aroclors, thus there is no need to know the source contaminating Aroclors a priori. Using the Frame et al. database of Aroclor congener distributions, 276 pairs of correlated congeners, constructed from 95 individual congeners, are identified. A comparison study of Aroclors and Hudson River sediments included 218 of the 276 tracker pairs. Conclusive evidence of a shift in the congener proportions is found in 120 of the 218 cases, a much greater number than expected if no change in congener distribution had occurred.     

白酒模拟体系氢键缔合时效性核磁共振研究

采用氢谱核磁共振测定了40%和60%乙醇含量白酒模拟体系在190d时间范围内的氢键缔合情况。结果表明,随着储藏时间的延长,模拟体系的羟基质子峰不断向低场移动,说明体系内氢键缔合逐渐增强;不同乙醇含量的白酒模拟体系氢键缔合强度不同,低乙醇含量溶液的氢键缔合整体强于高乙醇含量溶液;而且二者出现缔合最强峰的时间也不相同,高乙醇含量溶液比低乙醇含量溶液较晚出现最强缔合。     

Amylose‐lipid complex formation during extrusion cooking: effect of added lipid type and amylose level on corn‐based puffed snacks

The effect of amylose‐lipid complex formation during extrusion was studied with respect to expansion characteristics and oxidative stability of the extrudates. Full factorial design was adopted to investigate the effects of variables, amylose (two levels, 25% and 45%), types of lipid (coconut oil, fish oil and MaxEPA) and levels of lipid (1.5% and 3%), on amylose‐lipid complex formation, expansion ratio, crispness, hardness and oxidative stability. Increased amylose content in feed mixture produced crispy extrudates with significantly higher (P < 0.05) amylose‐lipid complex formation, greater radial expansion, lower hardness and higher oxidative stability. Amylose‐lipid complex formation and its complimentary effect, that is, oxidative stability were significantly higher in extrudates incorporated with coconut oil compared to those with fish oil or MaxEPA. However, better physical properties viz. radial expansion, crispness and lesser hardness were displayed by extrudates added with MaxEPA followed by those with fish oil. Between these two, fish oil‐incorporated extrudates exhibited significantly higher oxidative stability compared to MaxEPA incorporated products. Thus, the study demonstrates the usefulness of amylose rich corn flour to make oxidatively stable fish oil‐incorporated extrudates with better expansion characteristics.     

基于1 H NMR分析不同储存条件下大豆油的氧化稳定性

为探讨大豆油在不同包装材料以及有无抗氧化剂条件下的氧化稳定性,基于1H NMR分别对大豆油自动氧化过程中的一级氧化产物和二级氧化产物峰信号进行量化分析。以墨绿磨砂瓶、白色磨砂瓶、透明玻璃瓶包装的大豆油以及透明玻璃瓶包装的含TBHQ的大豆油作为试验对象,将4组油样置于充足日光灯光照的40 ℃烘箱中进行恒温氧化,定期取样进行1H NMR分析。结果表明：采用1H NMR可有效鉴别出大豆油中5种氧化产物,分别为一级氧化产物Z,E型和E,E型共轭烯烃类氢过氧化物,以及二级氧化产物正构醛、E,E-共轭二烯醛和E-共轭烯醛;利用1H NMR可有效监控氧化产物含量,经单因素ANOVA统计分析,抗氧化剂TBHQ（0.05 g/kg）对大豆油储存初期（70 d内）的一级氧化过程有显著的延缓作用（p＜0.05）,墨绿磨砂瓶包装（避光）对大豆油的二级氧化过程有显著的延缓作用（p＜0.05）。     

皮革柔软性的模糊评价方法研究

皮革柔软性的评价具有一定的模糊性。提出了皮革柔软性模糊综合评定方法。该方法综合考虑皮革在不同载荷下的顶伸性能 ,运用模糊数学的综合评价分析理论 ,对皮革柔软性进行了科学的、定量的、客观的评价。     

基于WinCC的小麦粉生产数据报表实现方法研究

对组态软件WinCC的报表功能进行分析的基础上,在WinCC6.2组态环境中,利用VBScript脚本和SOL数据库开发了小麦粉生产数据报表管理系统.并阐述了报表开发的详细步骤.实际应用表明,该方法是一种快捷有效的实现WinCC复杂数据报表方案.     

基于ADO的模具设计数据存储新方法

提出了一种基于零件类封装的存储数据新方法.该方法将产品数据识别存储与设计过程结合起来,通过ADO(activeX data objects)遍历零件类,从而获取模具零件属性参数并进行存储.实际使用结果表明,该方法便于修改模具参数,简单可靠,且能够提高产品设计的效率.     

A novel method to evaluate the applicability of time temperature integrators to different temperature profiles

The use of a Peltier device to provide controlled heating and cooling profiles to test the applicability of time temperature integrators (TTIs) has been evaluated. The α-amylase of Bacillus amyloliquefaciens has been used as a case study.Kinetic parameters of the enzyme were first determined as D_85 °C of 6.1 min ± 0.4 min and z of 12 °C ± 1.3 °C. Non-isothermal heat treatment processes were simulated with a Peltier thermoelectric module, and the P values found by assaying the TTI responses and integrating thermocouple temperature–time data compared. The response of the TTI responses correlated well with the thermocouples for non-isothermal processes: The two sets of P values were identical to ± 20%.The Peltier stage is shown to be useful in giving programmed temperature–time profiles that can be used to test the accuracy and application of TTIs.

Industrial relevance

Time temperature integrators (TTIs) are potentially very valuable for the measurement and validation of thermal processes. However, their industrial use requires their accuracy to be known to ensure that the results can be correctly interpreted. This paper gives a study of the accuracy of one such TTI.