New (1)h NMR procedure for the characterization of native and modified food-grade starches

A novel, fast, and straightforward procedure is presented for the characterization of starch (the largest energy component in food) and modified starches (such as octenyl succinic anhydride (OSA)-modified starches used as a dispersing agent in the food industry). The method uses (1)H NMR to measure the degree of branching and also, for modified starches, the degree of chemical substitution. The substrate is dissolved in dimethyl-d(6) sulfoxide; addition of a very low amount of deuterated trifluoroacetic acid (d(1)-TFA) to the medium gives rise to a shift to high frequency of the exchangeable protons of the starch hydroxyl groups, leading to a clear and well-defined (1)H NMR spectrum, which provides an improved way to determine the degrees of both branching and chemical substitution. Measurements of the size and molecular weight distributions by multiple-detector size exclusion chromatography show that degradation by TFA does not affect the accuracy of the method.     

Metabolite profiling using (1)H NMR spectroscopy for quality assessment of green tea, Camellia sinensis (L.)

A set of 191 green teas from different countries was collected and analyzed by (1)H NMR. It was proposed to establish if the teas could be discriminated according to the country of origin or with respect to quality. Both principal component analysis (PCA) and cluster analysis were applied to the data. Some separation of Chinese and non-Chinese teas was observed. The present results did not allow allocation of samples to individual countries, but cluster analysis suggested that it might be possible with an augmented sample set. The PCA did show a separation between the Longjing type (highest quality Chinese tea) and most other Chinese teas and indicated some metabolites that could be responsible for the difference. Longjing teas showed higher levels of theanine, gallic acid, caffeine, epigallocatechin gallate, and epicatechin gallate and lower levels of epigallocatechin when compared with other teas. These compounds have been mentioned previously in connection with quality, but it was also shown that higher levels of theogallin (5-galloyl quinic acid), theobromine, 2-O-(beta-l-arabinopyranosyl)-myo-inositol and some minor sugar-containing compounds were found in Longjing teas while higher levels of fatty acids and sucrose were found in the other teas. These new markers could prove to be useful for the authentication of bulk tea.     

Bioactive compounds in cod (Gadus morhua) products and suitability of 1H NMR metabolite profiling for classification of the products using multivariate data analyses

This work investigates the suitability of (1)H NMR spectroscopy to identify the fate of some bioactive compounds in seafood submitted to several processing conditions and examines the possibility of using (1)H NMR spectroscopy profiling to classify such products. Perchloric acid extracts of cod white muscle from newly killed and (i) unprocessed, (ii) boiled, and (iii) fried fillets and from (iv) frozen fillets, (v) the frozen fillets after thawing, and (vi) their drip loss and from (vii) rehydrated cod klippfish (n = 5) were analyzed by 500 MHz (1)H NMR spectroscopy. It was possible to identify taurine, betaine, anserine, creatine, and trimethylamine oxide (TMAO) in all extracts examined, and frozen fish was recognizable by the presence of dimethylamine (DMA). None of the heating procedures seemed to induce the loss of bioactive compounds from the fillet, but freezing and thawing did: the compounds were lost in what is known as drip loss. About 80% of the samples were correctly classified using a probabilistic neural network procedure having as inputs the scores of the first 20 principal components of the principal component analysis of a selected region of the NMR spectra.     

Multivariate analysis of NMR and FTIR data as a potential tool for the quality control of beer

In this work, principal component analysis (PCA) is applied to the FTIR-ATR and the (1)H NMR spectra of 50 beers differing in label and type (ale, lager, alcohol-free), to identify the spectral parameters that may provide rapid information about factors affecting beer production. PCA of FTIR data resulted in the separation of beers mainly according to their alcoholic content, providing little information on components other than ethanol contributing to the variability within the samples. PCA of (1)H NMR spectra, performed on the region where major beer components resonate (3.0-6.0 ppm), resulted in the separation of samples into four groups: two groups characterized by the predominance of dextrins, one group of alcohol-free beers characterized by the predominance of maltose, and one group where glucose was found to predominate. By performing PCA on aliphatic and aromatic regions, the contribution of minor components was highlighted. In particular, most ales, lagers, and alcohol-free samples could be distinguished based on their aromatic composition, thus reflecting the high sensitivity of the low-field NMR region toward different types of beer fermentation.     

Caffeine and resistance of coffee to the berry borer Hypothenemus hampei (Coleoptera: Scolytidae)

The role of caffeine as a chemical defense of coffee against the berry borer Hypothenemus hampei was investigated. No positive correlation was observed between resistance and caffeine content in experiments in which seeds from several coffee species presenting genetic variability for the alkaloid were exposed to adult insects. The same was observed in an experiment with coffee seeds that had their caffeine content doubled by imbibition with caffeine aqueous solutions. Other experiments showed that the attractiveness to insects was not related to the caffeine content of mature fruits. These results indicate that H. hampei has evolved an adaptation to handle the toxic effects of caffeine.     

Water distribution in brine salted cod (Gadus morhua) and salmon (Salmo salar): a low-field 1H NMR study

Low-field (LF) (1)H NMR T 2 relaxation measurements were used to study changes in water distribution in lean (Atlantic cod) and fatty (Atlantic salmon) fish during salting in 15% NaCl and 25% NaCl brines. The NMR data were treated by PCA, continuous distribution analysis, and biexponential fitting and compared with physicochemical data. Two main water pools were observed in unsalted fish, T 21, with relaxation times in the range 20-100 ms, and T 22, with relaxation times in the range 100-300 ms. Pronounced changes in T 2 relaxation data were observed during salting, revealing changes in the water properties. Salting in 15% brine lead to a shift toward longer relaxation times, reflecting increased water mobility, whereas, salting in saturated brines had the opposite effect. Water mobility changes were observed earlier in the salting process for cod compared to salmon. Good linear correlations ( F 相似文献   

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.     

Volatile composition of coffee berries at different stages of ripeness and their possible attraction to the coffee berry borer Hypothenemus hampei (Coleoptera: Curculionidae)

The analysis of volatile emissions of coffee berries in different physiological states of ripeness was performed using dynamic headspace and gas chromatography/mass spectrometry analysis for Coffea arabica, var. Colombia. The composition of the volatiles emitted by coffee berries is dominated by very high levels of alcohols, mainly ethanol, in all stages of ripeness in comparison with other compounds. Overripe coffee berries have high volatile emissions and show a composition dominated mainly by esters followed by alcohols, ketones, and aldehydes. The lowest level compounds were monoterpenes. 2-Methyl furan was detected in various ripening stages; this compound has not been previously reported as a coffee berry volatile. The presence of ethanol and other alcohols in the volatile composition might explain the effectiveness of using traps with mixed alcohols for detection and capture of coffee berry borers.     

1H NMR metabolite fingerprint and pattern recognition of mullet (Mugil cephalus) bottarga

Nuclear magnetic resonance (NMR) spectroscopy combined with multivariate data analysis (MVA) was used to investigate the molecular components of the aqueous extract of samples of bottarga, that is, salted and dried mullet (Mugil cephalus) roe, manufactured in Sardinia (Italy) from mullets of known and unknown geographical provenience. Principal component analysis (PCA) applied to the processed (1)H NMR spectra indicated that samples tend to cluster according to their geographical origin and also on the basis of storage and manufacturing procedures. The most important metabolites that characterized grouping of samples are the free amino acids methionine (Met), glutamate (Glu), histidine (His), phenylalanine (Phe), tyrosine (Tyr), and isoleucine (Ile); trimethylamine (TMA) and dimethylamine (DMA), both biomarkers of degradation; nucleotides and derivatives; choline (Cho) and phosphorylcholine (P-cho); and lactate (Lac).     

Pathways for the hydrolysis of phorate: product studies by (31)P NMR and GC-MS

A new intramolecular mechanism is proposed for the hydrolysis of phorate. (31)P NMR was used to study the formation of P-containing products of phorate hydrolysis in situ. When hydrolysis was followed by (31)P NMR, a dominant P-containing product was found and was identified to be diethyl dithiophosphate using methylation and GC-MS. Combining the data from phorate hydrolysis at three different temperatures, thermodynamic parameters were calculated. The contributions of various possible pathways to phorate hydrolysis are discussed.     

Application of (31)P NMR spectroscopy in food analysis. 1. Quantitative determination of the mono- and diglyceride composition of olive oils

This paper introduces a facile method to determine the amount of mono- and diglycerides in virgin olive oils. This method is based on the phosphorylation of the free hydroxyls of the mono- and diglycerides with 2-chloro-4,4,5,5-tetramethyldioxaphospholane and the integration of the appropriate peaks in the (31)P NMR spectrum. Quantitative (31)P NMR spectroscopy can be extended to the quantification of other constituents of olive oils bearing functional groups with labile protons.     

Quantification of kavalactones and determination of kava (Piper methysticum) chemotypes using near-infrared reflectance spectroscopy for quality control in vanuatu

Kava ( Piper methysticum Forst f., Piperaceae) has anxiolytic properties and the ability to promote a state of relaxation without the loss of mental alertness. The rapid growth of the nutraceutical market between 1998 and 2000 has been stopped by a ban in Europe and Australia because of some suspicion of liver toxicity. It is now important to develop a fast, cheap, and reliable quality test to control kava exports. The aim of this study is to develop a calibration of the near-infrared reflectance spectroscopy (NIRS) using partial least-squares (PLS) regression. Two hundred thirty-six samples of kava roots, stumps, and basal stems were collected from the Vanuatu Agricultural Research and Technical Centre germplasm collection and from four villages. These samples, representing 45 different varieties, were analyzed using NIRS to record their absorption spectra between 400 and 2500 nm. A set of 101 selected samples was analyzed for their kavalactone content using HPLC. The results were used for PLS calibration of the NIRS. The NIRS prediction of the kavalactone content and the dry matter were in agreement with the HPLC results. There were good correlations between these two series of results, and coefficients ( R (2)) were all close to 1. The measurements were reproducible and had repeatability on par with the HPLC method. The NIRS system has been calibrated for the six major kavalactone content measurements, and it is suggested that this method could be used for quality control in Vanuatu.     

Determination of the N-glycosylation patterns of seed proteins: applications to determine the authenticity and substantial equivalence of genetically modified (GM) crops

Methods have been developed to determine the N-glycosylation pattern of proteins at the single-seed level in two different biological systems. These were the well-characterized and widely consumed storage protein phaseolin from several species of Phaseolus (bean) and the α-amylase inhibitor from the same Phaseolus species expressed transgenically in pea. The N-glycosylation pattern of the α-amylase inhibitor expressed transgenically in pea was different from that of the inhibitor present in common bean (P. vulgaris), the species of origin of the gene. However, multivariate analysis showed that the differences in N-glycan patterns between the α-amylase inhibitors from common bean and pea were less than those between the inhibitors from common bean and two related bean species, lima bean (Phaseolus lunatus) and tepary bean (Phaseolus acutifolius).     

Study of interactions between food phenolics and aromatic flavors using one- and two-dimensional (1)H NMR spectroscopy

Changes in flavor release and aroma characteristics in a medium including food phenolics may be attributed to an intermolecular interaction between flavor compounds and phenolics. To investigate the interaction, one- and two-dimensional NMR studies have been carried out on the binding of two phenolics, gallic acid and naringin, with three aroma compounds, 2-methylpyrazine, vanillin, and ethyl benzoate. Evaluation of thermodynamic parameters and intermolecular nuclear Overhauser effects reveals that gallic acid can interact more strongly with aromatic flavors than naringin. The supramolecular complexation is also dependent on the structural nature of the flavors, with 2-methylpyrazine and vanillin interacting more strongly than ethyl benzoate. The interaction is principally pi-pi stacking between the galloyl ring and the aromatic ring of the aroma compounds, but secondary hydrogen-bonding effects help to stabilize the complex and enhance the specificity.     

Regression statistics as a tool to evaluate excess (anthropogenic) phosphorus,nitrogen, and organic matter in classification of Swedish fresh water quality

Concentrations of phophorus, nitrogen, COD_Mn, and humic matter in streams from small protected Swedish watersheds have been used to build statistical models useful in the evaluation of the state of the water quality. The precision of the models has been tested on data sets from other SEPA (Swedish Environmental Protection Agency) reference programs as well as international data sets. The models refer to watersheds, where most of the samples have a pH above 5.0. For the nutrients two delimitations have been defined. The lowest delimitation,the most likely upper limit for pristine concentration, corresponds to the models estimate minus 1 standard error. The highest delimitation,the most likely upper limit for none or insignificant influence, corresponds to twice the lowest delimitation, which also can be considered as a management concentration [c _m]. The calulated export coefficients for phosphorus agree with coefficients reported in the literature. The export coefficients for nitrogen seems to be dependent on the atmospheric deposition of nitrogen. A nutrient pollution index (NPI) has been calibrated against existing trophic state classification systems. The NPI for phosphorus show a considerable decrease in southern Sweden since the inroduction of chemical treatment plants. The nirogen conditions have not been improved to the same extent.     

Evaluation of Eucalyptus Camaldulensis (river GUM) and Chamaecytisus Proliferu (Tagasaste) for salinity control by agroforestry

Components of the soil water balance were measured over a three year period for Eucalyptus camaldulenis and Chamaecytisus proliferus, species commonly used for revegetation in Western Australia, and compared with water balance components for pasture. Marked seasonal trends in evapotranspiration were observed for all species with maxima occurring in the wet months, and minima occurring in summer when rainfall was low and evaporative demand high. in each year of study, annual evapotranspiration and soil water depletions were greater for both tree species than for the pasture, due to the greater extraction of soil water at depth. Upward movement of water from the saturated zone was also found to be greater beneath the deeper rooted perennials than beneath pasture.     

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.     

In situ analysis and structural elucidation of sainfoin (Onobrychis viciifolia) tannins for high-throughput germplasm screening

A rapid thiolytic degradation and cleanup procedure was developed for analyzing tannins directly in chlorophyll-containing sainfoin ( Onobrychis viciifolia ) plants. The technique proved suitable for complex tannin mixtures containing catechin, epicatechin, gallocatechin, and epigallocatechin flavan-3-ol units. The reaction time was standardized at 60 min to minimize the loss of structural information as a result of epimerization and degradation of terminal flavan-3-ol units. The results were evaluated by separate analysis of extractable and unextractable tannins, which accounted for 63.6-113.7% of the in situ plant tannins. It is of note that 70% aqueous acetone extracted tannins with a lower mean degree of polymerization (mDP) than was found for tannins analyzed in situ. Extractable tannins had between 4 and 29 lower mDP values. The method was validated by comparing results from individual and mixed sample sets. The tannin composition of different sainfoin accessions covered a range of mDP values from 16 to 83, procyanidin/prodelphinidin (PC/PD) ratios from 19.2/80.8 to 45.6/54.4, and cis/trans ratios from 74.1/25.9 to 88.0/12.0. This is the first high-throughput screening method that is suitable for analyzing condensed tannin contents and structural composition directly in green plant tissue.     

Detection of beef and poultry by serological field screening tests (ORBIT and PROFIT): collaborative study

Ten laboratories each analyzed 30 raw meat and raw meat product samples in a collaborative study of the ORBIT (overnight rapid bovine identification test) and PROFIT (poultry rapid overnight field identification test) serological field screening tests for the detection of beef and poultry. Versatility of the tests was shown in the analysis of whole tissue, ground, or emulsified raw meat products. Both tests were demonstrated to be reliable and were capable of detecting adulterants present at the 10% level. The method has been adopted official first action.     

Effectiveness and geomorphological impacts of check dams for soil erosion control in a semiarid Mediterranean catchment: El Cárcavo (Murcia, Spain)

The construction of transverse structures (check dams) is a widely used method in Spanish Mediterranean areas to stabilise gullies and ephemeral streams, to reduce channel incision and to prevent sediment deposition downstream. The effectiveness of check dams and their effects on the morphology of ephemeral channels (ramblas) were investigated in a semiarid, highly degraded catchment. In the study area, 36 dams were surveyed, of which 29 were filled up with sediments, 2 had been destroyed and only 5 had still not completely filled with sediments. The streams above the dams held sediments, which resulted in a decrease in the longitudinal gradient. Field observations of changes in the cross-sectional shape of the stream channel, the composition of channel bed material, and bankfull stage measurements indicated that the dams cause erosion downstream. The amount of sediments stored by the dams was found to be higher than the amount of eroded material in the downstream reaches of the dam.