Mobility characterization of waxy corn starch using wide-line (1)H nuclear magnetic resonance

The molecular mobility of waxy corn starch was studied by using wide-line (1)H nuclear magnetic resonance (NMR) spectroscopy. A suite of NMR techniques was used to measure relaxation times (i.e., T(2), T(2), and T(1)) and to characterize water and solid (starch) mobility of waxy corn starch. It was observed that the spectrum of each sample includes a complex broad proton component upon which is superimposed a narrow proton component over water activity (a(w)) ranges from 0.33 to 0.97 (i.e., 10.-25.6% water content) at 25 degrees C. Line shape analysis and relaxation times of both broad and narrow components show that T(2) and T(2) values decrease (i.e., decreasing mobility) with increasing solid concentration and show a "break point" in a concentration range between 19.8 and 21.9% water content. The T(1) shows a "T(1) minimum" in the same concentration range. Starch samples change from the glassy to viscous rubbery state in this same concentration range. This demonstrates that wide-line (1)H NMR relaxation times (i.e., T(2), T(2), and T(1)) may be useful as indicators of glass transition for starch samples in the solid state. The results demonstrate that wide-line (1)H NMR spectroscopy is able to separate modes and quantitate the magnitude of molecular mobility in complex systems.     

Application of cryoprobe 1H nuclear magnetic resonance spectroscopy and multivariate analysis for the verification of corsican honey

Proton nuclear magnetic resonance spectroscopy ((1)H NMR) and multivariate analysis techniques have been used to classify honey into two groups by geographical origin. Honey from Corsica (Miel de Corse) was used as an example of a protected designation of origin product. Mathematical models were constructed to determine the feasibility of distinguishing between honey from Corsica and that from other geographical locations in Europe, using (1)H NMR spectroscopy. Honey from 10 different regions within five countries was analyzed. (1)H NMR spectra were used as input variables for projection to latent structures (PLS) followed by linear discriminant analysis (LDA) and genetic programming (GP). Models were generated using three methods, PLS-LDA, two-stage GP, and a combination of PLS and GP (PLS-GP). The PLS-GP model used variables selected by PLS for subsequent GP calculations. All models were generated using Venetian blind cross-validation. Overall classification rates for the discrimination of Corsican and non-Corsican honey of 75.8, 94.5, and 96.2% were determined using PLS-LDA, two-stage GP, and PLS-GP, respectively. The variables utilized by PLS-GP were related to their (1)H NMR chemical shifts, and this led to the identification of trigonelline in honey for the first time.     

Oil stability prediction by high-resolution (13)C nuclear magnetic resonance spectroscopy

(13)C NMR spectra of oil fractions obtained chromatographically from 66 vegetable oils were obtained and analyzed to evaluate the potential use of those fractions in predicting oil stabilities and to compare those results with oil stability prediction by using chemical determinations. The oils included the following: virgin olive oils from different cultivars and regions of Europe and north Africa; "lampante" olive, refined olive, refined olive pomace, low-erucic rapeseed, high-oleic sunflower, corn, grapeseed, soybean, and sunflower oils. Oils were analyzed for fatty acid and triacylglycerol composition, as well as for phenol and tocopherol contents. By using stepwise linear regression analysis (SLRA), the chemical determinations and the (13)C NMR data that better explained the oil stability determined by the Rancimat were selected. These selected variables were related to both the susceptibility of the oil to be oxidized and the content of minor components that most contributed to oil stability. Because (13)C NMR considered many more variables than those determined by chemical analysis, the predicted stabilities calculated by using NMR data were always better than those obtained by using chemical determinations. All these results suggest that (13)C NMR may be a powerful tool to predict oil stabilities when applied to chromatographically enriched oil fractions.     

Molecular characterization around a glassy transition of starch using (1)H cross-relaxation nuclear magnetic resonance

The aim of this work was to characterize the glassy-rubbery transition in starch gels using molecular (NMR) techniques. Proton cross-relaxation ((1)H CR) NMR spectra of gelatinized starch ( approximately 50% mc) were obtained by cooling stepwise from 20 to -30 degrees C. A significant line broadening was observed in the CR spectra between 0 and -10 degrees C. Deconvolution of the spectra into its component curves (broad and narrow) yielded a peak amplitude, width at half-height, and peak area for each curve. Between 0 and -10 degrees C (temperatures around T(g)), a significant line width change in the broad component (rigid solid) was apparent. These observed qualitative changes may be evidence of a glassy-rubbery transition at a molecular (short-range) level which are strengthened by a similar transition temperature range found previously with (13)C CP-MAS and DMA tan delta(T) measurements. However, the increase in the relative quantity of rigid protons observed by (1)H CR NMR spectra could also be attributed to ice. The (1)H CR NMR method showed its potential application for probing solid components in gels using a simple and economical NMR spectrometer, without the need for a solid-state instrument.     

Detection of primary and secondary oxidation products by Fourier transform infrared spectroscopy (FTIR) and 1H nuclear magnetic resonance (NMR) in sunflower oil during storage

The oxidation of sunflower oil, stored in closed receptacles at room temperature for a period of 10 years, was monitored using Fourier transform infrared spectroscopy (FTIR) and 1H nuclear magnetic resonance (NMR). The objective was to understand the evolution of the oxidation process in sunflower oil under the conditions above mentioned. These techniques provide information about the oxidative status of several oil samples and the primary and some of the secondary oxidation products formed in the oxidation process. The results obtained show that, under these conditions, sunflower oxidation takes place in a different way to that at higher temperatures with aeration. The 1H NMR spectra show that in the first oxidation stages of the process only hydroperoxides supporting cis, trans-conjugated double bonds are formed and that at more advanced stages hydroperoxides having trans, trans-conjugated double bonds are generated, with the latter always being in a smaller proportion than the former. In addition, the presence of hydroxy derivatives supporting cis, trans-conjugated double bonds among the primary oxidation compounds is shown for the first time. Also, from early oxidation stages onward and unlike the process at 70 degrees C with aeration, it is noticeable that 4-hydroxy- trans-2-alkenals are formed in much higher proportions than 4-hydroperoxy- trans-2-alkenals. This fact could be associated with the presence of hydroxy derivatives with cis, trans-conjugated double bonds among the primary oxidation products and the limited concentration of oxygen during the oxidation. Furthermore, relationships between some oxidation conditions and the oxidation level of the samples were statistically analyzed.     

High-resolution (13)C nuclear magnetic resonance spectroscopy pattern recognition of fish oil capsules

13C NMR (nuclear magnetic resonance) spectroscopy, in conjunction with multivariate analysis of commercial fish oil-related health food products, have been used to provide discrimination concerning the nature, composition, refinement, and/or adulteration or authentication of the products. Supervised (probabilistic neural networks, PNN) and unsupervised (principal component analysis, PCA; Kohonen neural networks; generative topographic mapping, GTM) pattern recognition techniques were used to visualize and classify samples. Simple PCA score plots demonstrated excellent, but not totally unambiguous, class distinctions, whereas Kohonen and GTM visualization provided better results. Quantitative class predictions with accuracies >95% were achieved with PNN analysis. Trout, salmon, and cod oils were completely and correctly classified. Samples reported to be salmon oils and cod liver oils did not cluster with true salmon and cod liver oil samples, indicating mislabeling or adulteration.     

1H nuclear magnetic resonance-based metabolomic characterization of wines by grape varieties and production areas

(1)H NMR spectroscopy was used to investigate the metabolic differences in wines produced from different grape varieties and different regions. A significant separation among wines from Campbell Early, Cabernet Sauvignon, and Shiraz grapes was observed using principal component analysis (PCA) and partial least squares-discriminant analysis (PLS-DA). The metabolites contributing to the separation were assigned to be 2,3-butanediol, lactate, acetate, proline, succinate, malate, glycerol, tartarate, glucose, and phenolic compounds by PCA and PLS-DA loading plots. Wines produced from Cabernet Sauvignon grapes harvested in the continental areas of Australia, France, and California were also separated. PLS-DA loading plots revealed that the level of proline in Californian Cabernet Sauvignon wines was higher than that in Australian and French Cabernet Sauvignon, Australian Shiraz, and Korean Campbell Early wines, showing that the chemical composition of the grape berries varies with the variety and growing area. This study highlights the applicability of NMR-based metabolomics with multivariate statistical data sets in determining wine quality and product origin.     

Metabolic profiling of potential probiotic or synbiotic cheeses by nuclear magnetic resonance (NMR) spectroscopy

To assess ripening of potential probiotic cheeses (containing either Lactobacillus casei -01 or Bifidobacterium lactis B94) or synbiotic cheeses with fructooligosaccharides (FOS) or a 50:50 mix of FOS/inulin, metabolic profiles have been obtained via classical biochemical analyses and by NMR spectroscopy. The addition of prebiotics to the cheeses resulted in lower proteolysis indices, especially in those synbiotic cheeses inoculated with B. lactis B94. Among synbiotic cheeses the combination of FOS and inulin resulted in an increase in lipolytic activity. The metabolic profiles of the cheeses analyzed by NMR spectroscopy, combined with multivariate statistics, allowed profiles to be distinguished by maturation time, added probiotic bacteria, or, in the case of B. lactis B94 cheese, added prebiotic. The NMR results are in agreement with the biochemical analyses and demonstrate the potential of NMR for the study of metabolic processes in probiotic/synbiotic food matrices.     

Quantification of inositol phosphates using (31)P nuclear magnetic resonance spectroscopy in animal nutrition

A (31)P NMR method for quantitative determination of inositol phosphates in simple incubation samples of sodium phytate and Aspergillus niger phytase and in different types of complex samples, such as diets, digesta, and feces, is described. The inositol phosphates in complex samples were extracted with HCl, concentrated, and purified using freeze-drying and filtration and subsequently determined at pH 12.6 in aqueous solution using a (31)P NMR method. The (31)P NMR technique has as its main advantages over the HPLC techniques that it does not necessitate standards that may cause background matrix effects and that the spectra of inositol phosphates and orthophosphate appear in the same run without further sampling errors. The results of inositol hexaphosphate analysis with HPLC can be confirmed by this (31)P NMR method. Contents of inositol tetra-, tri-, di-, and monophosphate in the biological samples appear to be quantitatively not important. The (31)P NMR method can be applied for use in animal nutrition in general and studies of using phytase in diets for farm animals in particular, by measuring the content of inositol phosphates in feed ingredients, complete feeds, ileal contents, and feces of pigs and poultry.     

Determination of the composition of gentamicin sulfates by 1H and 13C nuclear magnetic spectroscopy

The British Pharmacopoeia test controlling the composition of gentamicin sulfate is based on CW 60 MHz magnetic resonance spectroscopy. Application of this method to FT 90 MHz spectra was evaluated. Results clearly show the limitations of this technique and point out the need for more reliable assay methods. Thus a 13C nuclear magnetic resonance (NMR) procedure for quantitative analysis of gentamicin sulfate was developed. Ratios of 4 gentamicin components (C1, C2, C1a, and C2a) were obtained from peak height measurements of selected resonance signals in spectra recorded under steady-state conditions. Relative response factors were determined from spectra of a reference mixture or, alternatively, from spectra of the individual pure components. Results obtained by the 13C NMR method were in agreement with those obtained by liquid chromatography using pre-column derivatization.     

High-resolution nuclear magnetic resonance spectroscopy and multivariate analysis for the characterization of beer

Beer contains a very complex mixture of nutrients, which in this work are identified to some extent by high-field high-resolution nuclear magnetic resonance (NMR) one- and two-dimensional methods. The (1)H NMR spectrum of beer shows a predominance of strongly overlapped peaks arising from several carbohydrates. Minor components are clearly observed both in the aliphatic and in the aromatic regions of the spectrum. With the aid of two-dimensional methods, spectral assignment was carried out, enabling the identification of approximately 30 compounds and identifying about the same number of spin systems for further assignment. The variability of the spectral profile of beers differing in type and label was studied by principal component analysis (PCA), and it was found that, although some distinction is achieved on the basis of the aliphatic and sugar compositions, clearer separation between ales and lagers is obtained by PCA of the aromatic profiles alone. The potential of this technique as a rapid and informative quality control tool is discussed.     

1H nuclear magnetic resonance relaxometry study of water state in milk protein mixtures

1H NMR signal was used to characterize highly hydrated milk protein dispersions (3-20% dry matter) with various micellar casein concentrations (3-15%), whey protein concentrations (0-3%), lactose concentrations (0-7.5%), CaCl(2) concentrations (0-2 mM), and pH (6.2-6.6). The results showed the predominant effect of micellar casein concentration on water state and were consistent with the three-site relaxation model in the absence of lactose. The relaxation rates observed for these dispersions were explained by the free water relaxation rate, the hydration water relaxation rate, and the exchangeable proton relaxation rate. Hydration water was found to be mainly influenced by casein micelle concentration and structure. The variations in hydration with pH were consistent with those observed for classical measurement of voluminosity observed at this range of pH. The effects of lactose and whey protein content are discussed.     

基于低场核磁共振的热风干燥猕猴桃切片含水率预测模型

为研究猕猴桃切片热风干燥过程中水分迁移规律,该试验通过对猕猴桃切片进行热风干燥,考察不同干燥温度（70、80、90 ℃）、切片厚度（3、4、5 mm）下的干燥特性。试验采用直接干燥法测定含水率,运用低场核磁共振技术（Low-Field Nuclear Magnetic Resonance,LF-NMR）分析热风干燥过程中猕猴桃切片内部水分分布状态与变化规律,建立动力学模型,验证并预测。结果表明：猕猴桃切片热风干燥开始为外部控制,随后属于内部扩散控制,水分有效扩散系数范围为1.58×10-7～4.18×10-7 m2/s,扩散效率随温度升高而增大。升高温度能显著提高猕猴桃干燥速率,可加快结合水、不易流动水以及自由水的迁移。自由水和结合水先于不易流动水发生变化,自由水含量在干燥前期逐渐下降,此过程中不易流动水和结合水含量均表现为先升高后降低的趋势。当自由水被脱除后,不易流动水和结合水含量依次达到最大值;此后,随着干燥的进行,不易流动水逐渐被脱除,此时结合水含量开始下降直至干燥结束。整个干燥过程中,猕猴桃切片部分自由水先转化为不易流动水和结合水,结合水与不易流动水相互转化,循环往复伴随整个干燥过程。以干燥过程中的自由水、结合水、不易流动水的核磁峰值总和、切片厚度和干燥温度为自变量,猕猴桃切片含水率为因变量,进行多元线性回归分析,建立含水率预测模型,模型的拟合优度为0.982。结果表明,低场核磁共振技术结合数学模型可用于描述猕猴桃切片热风干燥过程,可实现对猕猴桃切片干燥过程中含水率的快速、无损检测,研究结果可为猕猴桃热风干燥工艺和过程设计提供理论依据。     

Novel approach to the detection and quantification of phenolic compounds in olive oil based on 31P nuclear magnetic resonance spectroscopy

31P NMR spectroscopy has been employed to detect and quantify phenolic compounds in the polar fraction of virgin olive oil. This novel analytical method is based on the derivatization of the hydroxyl and carboxyl groups of phenolic compounds with 2-chloro-4,4,5,5-tetramethyldioxaphospholane and the identification of the phosphitylated compounds on the basis of the 31P chemical shifts. Quantification of a large number of phenolic compounds in virgin olive oil can be accomplished by integration of the appropriate signals in the 31P NMR spectrum and the use of the phosphitylated cyclohexanol as internal standard. Finally, the validity of this technique for quantitative measurements was thoroughly examined.     

利用低场核磁共振研究冷却条件对猪肉保水性的影响

为了通过水分分布信息,深入了解冷却条件对猪肉保水性的影响,以三元杂交猪为对象,利用低场核磁共振(LF-NMR)技术研究了不同冷却条件下猪肉的水分分布及流动规律。结果表明:冷却猪肉低场核磁共振自旋-自旋弛豫时间T2谱中出现4个水分峰,其横向弛豫时间分别为T20(150～500μs),T21(1～3ms),T22(40～50ms),T23(150～400ms)。滴水损失、蒸煮损失与T22,T23呈现显著正相关(P<0.01),自由水含量(pT23)与滴水损失的相关系数为0.858。冷却过程中不易流动水(pT22)先增加后减少,自由水(pT23)先减少后逐渐增加。与常规常湿冷却相比,两段式快速冷却使胴体的冷却失重降低了0.3%,高湿冷却使胴体的冷却失重降低了约0.5%,显著提高了保水性(P<0.05)。核磁成像显示,相对湿度95%处理组冷却猪肉表面的自由水比相对湿度80%处理组多。该研究结果对猪肉冷却工艺确定具有一定的指导作用。     

Efficient 1H nuclear magnetic resonance method for improved quality control analyses of Ginkgo constituents

We developed an analytical method using 1H nuclear magnetic resonance (NMR) spectrometry to resolve analytical problems with Ginkgo. After a simple hydrolysis step, an NMR analysis of the terpene trilactone H-12 signals and the flavonol aglycone H-2' (or H-2'/6' for kaempferol) signals was performed. By comparing the solvent effects on the resolution of these signals, methanol-d4-benzene-d6 (65:35) was selected as the optimal 1H NMR solvent. The amounts of terpene lactones and flavonol aglycones in various commercial Ginkgo products and Ginkgo leaves were determined. This newly developed 1H NMR method enables the simultaneous analysis of terpene trilactones and flavonols and allows simple, rapid quantification of these compounds in pharmaceutical Ginkgo preparations.     

Effect of dietary nitrogen content on the urine metabolite profile of dairy cows assessed by nuclear magnetic resonance (NMR)-based metabolomics

NMR-based metabolomics was applied on urine samples from 32 cows that were fed four levels of crude protein (124, 135, 151, and 166 g/kg DM, respectively) in a crossover design with the aim of identifying urinary metabolites related to nitrogen intake and nitrogen efficiency. Principal component analysis (PCA) on selected regions of the obtained (1)H NMR spectra revealed an effect of crude protein intake on NMR signals in the 0.5-3.0 and 5.0-10.0 ppm regions. Partial least-squares (PLS) regressions confirmed a correlation between the NMR metabolite profile and both nitrogen intake and efficiency. The NMR signals that correlated with nitrogen intake and efficiency included urea, hippurate, phenylacetylglutamine, and p-cresol sulfate, which all contributed to the prediction of nitrogen intake and efficiency. Thus, it was not possible to identify a single metabolite that could be used as a marker to predict nitrogen efficiency, and it can be concluded that a wide-ranging urinary metabolite profile is needed to evaluate nitrogen efficiency in ruminants.     

High-field nuclear magnetic resonance (NMR) study of truffles (Tuber aestivum vittadini)

A high-field NMR technique was used to analyze aqueous and organic extracts of truffles (Tuber aestivum vittadini) to characterize their chemical composition. Water-soluble metabolites belonging to different classes such as sugars, polyols, amino acids, and organic acids were almost completely assigned by means of one- and two-dimensional experiments (1H-1H COSY, TOCSY, 1H-13C HSQC, 1H-13C HMBC, and 1H-31P HMBC). The 1H spectral assignment of the cell membrane components such as lipids, sterols, and fatty acids extracted in organic solvents was also performed.     

Identification of amino acids in wines by one- and two-dimensional nuclear magnetic resonance spectroscopy

Amino acids are minor compounds in wines, but they have a profound influence on wine quality, and amino acids composition can be used to differentiate wines according to the vine variety, geographical origin, and year of production. The NMR signals of amino acids in NMR spectra are overlapped by the signals of other compounds present and especially by the signals of dominant compounds such as water, ethanol, and glycerol. In this work we used 1D (1)H and (13)C, 2D homonuclear COSY, TOCSY, and 2D heteronuclear HSQC and HMQC pulse sequences, also with an incorporated WET pulse sequence element that allows the simultaneous suppression of several frequencies. Complete (1)H and (13)C NMR assignments for 17 amino acids commonly present in wine and of gamma-aminobutyric acid at pH 3 have been achieved in wine sample of Sauvignon from the Coastal wine-growing region of Slovenia, vintage 1994.     

Quantitative determination of chlorpromazine. HCl in tablets, spansules, injectables, and bulk chemical by nuclear magnetic resonance spectroscopy

A nuclear magnetic resonance (NMR) procedure is described for the quantitative analysis of chlorpromazine. HCl in bulk chemical as well as in final dosage forms--tablets, spansules, and injectables. The method is based on measurement of a characteristic signal of chlorpromazine relative to an internal standard. Three different internal standards are specified: Cyclohexane was selected because of the convenience and rapidity with which samples could be prepared for assay. Piperonal was used to verify the method and to show that precision and accuracy were not affected by the volatility of the cyclohexane. Tetramethylammonium bromide was used as an internal standard for Thorazine injectable. No interferences were found from stearates and other tablet excipients. The NMR procedure provides a simple, direct, and specific assay with a precision of +/- 1-2%.