Element profiles of onion producing districts in Japan, as determined using INAA and PGA

We carried out instrumental neutron activation analysis (INAA) as well as k ₀-based prompt gamma-ray analysis (k ₀-PGA) to measure the amount of the elements in onions and studied whether the onions collected from different sites can be categorized based on the elemental concentration profile. Six elements (Na, Mg, Cl, K, Ca, Mn) and 3 elements (B, S, Cl) were measured by INAA and PGA in the onions grown in two districts, Hokkaido and Saga, in Japan, respectively. After principal component analysis, it was found that Cl was an important element to feature the producing districts of onions.     

Characterization of Vegetables by Stable Isotopic and Elemental Signatures

ABSTRACT

109 Romanian parsley, celery and parsnip root, cucumber, vegetable marrow, onion, and pepper samples were characterized by their stable isotope ratios and elemental concentrations in comparison to imported varieties. Organic and conventional agriculture practices were also compared as well as a differentiation between eggplant and peppers grown in greenhouses and those in the field. δ²H values were between ?70.8 and 5.6‰, while the δ¹⁸O values were between ?9.0 and 4.1‰. The δ¹⁵N values for white onions were from 2.8 to 11.1‰. For Romanian organic onions, the carbon isotopic values were lower (?29.2 to ?28.2‰) compared to conventional onions from other countries (?27.8‰ to ?23.8%). Linear discriminant analysis was used to characterize agricultural practices and the geographic origin of the vegetables.     

Chemometric techniques on inorganic elements composition for the determination of the geographic origin of Welsh onions.

Techniques to determine the producing country of Welsh onions (Allium fistulosum L.) were developed by using 216 samples from Japan and from Anchu Shandgon, Shanghai and Amoy Fjian in China. Twelve elements (Na, P, K, Ca, Mg. Mn, Fe, Cu, Zn, Sr, Ba, Al, Co, Ni, Rb, Mo, Cd, Cs, La, Ce, Tl and Pb) contained in Welsh onions were determined. In order to determining whether Welsh onions originate in Japan or in China, linear discriminant analysis (LDA) and soft independent modeling of class analogy (SIMCA) were performed, using concentrations of 20 elements excluding Al and Pb in 22 elements. In LDA for two-group discrimination modeled on Welsh onions from Japan and China, 103 samples used for modeling were classified 95% correctly, and 89 other samples were predicted 94% correctly. As the average of predictions by SIMCA modeled on samples selected by 10 times of random selections, 192 samples, including the 103 samples used for modeling, were predicted 96% correctly. In discriminations by combined LDA and SIMCA, all 81 samples produced in Japan were correctly judged to be Japanese ones, and only 8 samples out of 111 samples produced in China were not correctly judged to be Chinese ones.     

The Effects of Antioxidants on the Changes in Volatile Compounds in Heated Welsh Onions (Allium fistulosum L.) during Storage

Welsh onion (Allium fistulosum L.) is usually used to enhance the flavor characteristics of various foods. Volatile compounds in Welsh onions, including sulfur-containing compounds, may vary during heat process and storage. Accordingly, the changes in the volatile compounds in Welsh onions, subjected to heat and antioxidant (ascorbic acid and glutathione) treatments during storage, are investigated in the present study. The majority of sulfur-containing compounds in Welsh onions showed significant differences between the untreated Welsh onions and heated Welsh onions. During the heating of the Welsh onions, some sulfur-containing compounds, such as 2-methylthiirane, 1-(methyldisulfanyl)prop-1-ene, 1-[[(E)-prop-1-enyl]disulfanyl]propane, 1-(propyltrisulfanyl)propane, 1-[[(E)-prop-1-enyl]trisulfanyl]propane, and (methyltetrasulfanyl)methane, showed significant differences between the untreated and heated Welsh onions (p < 0.05). In addition, partial least square discriminant analysis (PLS-DA) was applied to discriminate the heated Welsh onion samples added with different antioxidants. The heated Welsh onion samples added with ascorbic acid was mainly associated with 2-phenylacetaldehyde, acetic acid, methylsulfanylmethane, prop-2-ene-1-thiol, undecan-2-one, and (2E,4E)-deca-2,4-dienal. Moreover, the key volatile compounds in the heated Welsh onion samples added with glutathione were 3-ethylthiophene, 1-(methyldisulfanyl)-1-methylsulfanylpropane, 1-methylsulfanylpentane, 2-prop-2-enylsulfanylpropane, and 1-propan-2-ylsulfanylbutane.     

多层碳纳米球的研究

用弧光放电法制备了碳的巴基葱.用原子力显微镜（AFM）、扫描隧道显微镜（STM）和透射电镜（TEM）研究了在高定向石墨(HOPG)和金(Au)基底上的巴基葱的行为和电学特性.扫描隧道谱表明,巴基葱的电学特性具有与单壁碳纳米管相似的非线性特性.较小尺寸的巴基葱呈半导体特性,尺寸增大倾向金属线性.AFM/STM图像显示,在HOPG和Au基底上的巴基葱能够聚集成二聚体.利用较小尺寸巴基葱的电学非线性特性,有希望构造纳米电子学的单电子器件.     

Metabolome-Based Discrimination Analysis of Shallot Landraces and Bulb Onion Cultivars Associated with Differences in the Amino Acid and Flavonoid Profiles

Shallot landraces and varieties are considered an important genetic resource for Allium breeding due to their high contents of several functional metabolites. Aiming to provide new genetic materials for the development of a novel bulb onion cultivar derived from intraspecific hybrids with useful agronomic traits from shallots, the metabolic profiles in the bulbs of 8 Indonesian shallot landraces and 7 short-day and 3 long-day bulb onion cultivars were established using LC–Q-TOF-MS/MS. Principal component analysis, partial least squares discriminant analysis, and dendrogram clustering analysis showed two major groups; group I contained all shallot landraces and group II contained all bulb onion cultivars, indicating that shallots exhibited a distinct metabolic profile in comparison with bulb onions. Variable importance in the projection and Spearman’s rank correlation indicated that free and conjugated amino acids, flavonoids (especially metabolites having flavonol aglycone), and anthocyanins, as well as organic acids, were among the top metabolite variables that were highly associated with shallot landraces. The absolute quantification of 21 amino acids using conventional HPLC analysis showed high contents in shallots rather than in bulb onions. The present study indicated that shallots reprogrammed their metabolism toward a high accumulation of amino acids and flavonoids as an adaptive mechanism in extremely hot tropical environments.     

Effect of hydrophobically modified polymers on shear-induced multilamellar vesicles

The effects of polymer concentration, polymer molecular weight, and hydrophobe substitution level of modified poly(acrylic acid) polymers on the formation, size, and viscoelastic properties of shear-induced multilamellar vesicles (onions) are studied by rheology and light diffraction. The onions are close-packed, space-filling vesicles formed by shearing aqueous lamellar phases of C12E5 surfactant to produce phases with sufficient order and size uniformity (O(1-3 microm)) to diffract light. The addition of hydrophobically modified polymers enhances the rate of formation, uniformity, and stability independent of hydrophobe substitution level. Onion size decreases with increasing shear rate as observed for pure surfactant onion systems, but the shear-rate dependence is changed by the polymer. The onion phase has a plateau modulus that increases with polymer concentration but is independent of hydrophobe substitution level or molecular weight. The model presented by Panizza et al. that relates the plateau modulus of the onion phase to membrane rigidity and the compression modulus is consistent with independent measurements of membrane properties from SANS.     

The effect of the physical matrix on accurate measurements using fixed volume analytical techniques

In order to perform high accuracy analytical measurements most analytical techniques require some form of calibration using standards of the same quantity as that being measured. The highest accuracy calibration standards are those prepared by mass (gravimetrically) as opposed to by volume (volumetrically). The use of gravimetrically prepared standards to calibrate analytical techniques that rely on fixed volume injections can cause systematic errors, even when the analytical technique does not suffer from a chemical matrix interference. The origin of these errors is explained and is demonstrated experimentally for the analysis of sulphate in synthetic seawater samples, and the measurement of the anionic content of particulate matter following extraction with water and wetting agents; where average measurement biases of +2.7 and -3.2%, respectively, were observed. Proposals are offered for methods to overcome this 'physical matrix effect'.     

Monitoring of substrate and product concentrations in acetic fermentation processes for onion vinegar production by NIR spectroscopy: value addition to worthless onions

Wastes and by-products of the onion-processing industry pose an increasing disposal and environmental problem and represent a loss of valuable sources of nutrients. The present study focused on the production of vinegar from worthless onions as a potential valorisation route which could provide a viable solution to multiple disposal and environmental problems, simultaneously offering the possibility of converting waste materials into a useful food-grade product and of exploiting the unique properties and health benefits of onions. This study deals specifically with the second and definitive step of the onion vinegar production process: the efficient production of vinegar from onion waste by transforming onion ethanol, previously produced by alcoholic fermentation, into acetic acid via acetic fermentation. Near-infrared spectroscopy (NIRS), coupled with multivariate calibration methods, has been used to monitor the concentrations of both substrates and products in acetic fermentation. Separate partial least squares (PLS) regression models, correlating NIR spectral data of fermentation samples with each kinetic parameter studied, were developed. Wavelength selection was also performed applying the iterative predictor weighting–PLS (IPW-PLS) method in order to only consider significant spectral features in each model development to improve the quality of the final models constructed. Biomass, substrate (ethanol) and product (acetic acid) concentration were predicted in the acetic fermentation of onion alcohol with high accuracy using IPW-PLS models with a root-mean-square error of the residuals in external prediction (RMSEP) lower than 2.5% for both ethanol and acetic acid, and an RMSEP of 6.1% for total biomass concentration (a very satisfactory result considering the relatively low precision and accuracy associated with the reference method used for determining the latter). Thus, the simple and reliable calibration models proposed in this study suggest that they could be implemented in routine applications to monitor and predict the key species involved in the acetic fermentation of onion alcohol, allowing the onion vinegar production process to be controlled in real time.     

Development of an analytical method for antimony speciation in vegetables by HPLC-hydride generation-atomic fluorescence spectrometry

A new method for antimony speciation in terrestrial edible vegetables (spinach, onions, and carrots) was developed using HPLC with hydride generation-atomic fluorescence spectrometry. Mechanical agitation and ultrasound were tested as extraction techniques. Different extraction reagents were evaluated and optimal conditions were determined using experimental design methodology, where EDTA (10 mmol/L, pH 2.5) was selected because this chelate solution produced the highest extraction yield and exhibited the best compatibility with the mobile phase. The results demonstrated that EDTA prevents oxidation of Sb(III) to Sb(V) and maintains the stability of antimony species during the entire analytical process. The LOD and precision (RSD values obtained) for Sb(V), Sb(III), and trimethyl Sb(V) were 0.08, 0.07, and 0.9 microg/L and 5.0, 5.2, and 4.7%, respectively, for a 100 microL sample volume. The application of this method to real samples allowed extraction of 50% of total antimony content from spinach, while antimony extracted from carrots and onion samples ranged between 50 and 60 and 54 and 70%, respectively. Only Sb(V) was detected in three roots (onion and spinach) that represented 60-70% of the total antimony in the extracts.     

Distribution of deoxynivalenol in wheat,wheat flour,bran, and gluten,and variability associated with the test procedure

Analytical data obtained on deoxynivalenol (DON) concentration in naturally contaminated wheat during processing in an industrial mill were statistically analyzed, and the distribution functions of DON concentration in lots of wheat, bran, wheat flour, and gluten were estimated. The analytical method had acceptable precision (HORRAT 0.25-0.32) for each test sample. The total variance combined sampling, sample preparation, and analytical variances were 0.188, 0.033, 0.42, and 0.0014 ppm2 for wheat, 1.93; flour, 0.99; bran, 4.68; and gluten, 0.29, respectively. The distribution function of DON contamination presented an asymmetric tail for high values of concentration in wheat grains and wheat flour; in bran it seemed to be bimodal with 2 separated peaks of different concentrations; in gluten the normal distribution function gave a reasonably good fit to empirical data. The function eta(c) = -In(-Inp), where p (c) is the cumulative distribution function was linear with c in the so-called extreme-value type I distribution and could be fitted by a cubic polynomial in c in the distributions determined for all the products. This variability and distributional information contributes to the design of better sampling plans in order to reduce the total variability and to estimate errors in the evaluation of DON concentration in lots of wheat and wheat products.     

Evaluation of microwave-assisted extraction for the analysis of organophosphorus and pyrethroid pesticides in green onions

The aim of this study was to evaluate the efficiency of microwave-assisted extraction (MAE) for the analysis of organophosphorus (OP) and pyrethroid (PYR) pesticides in green onions by GC/MS. We optimized MAE extraction solvent, temperature, and time by using a certified reference material. As a result, the concentrations of two OP and two PYR target pesticides obtained by MAE with acetonitrile at 110 degrees C for 10 min were in good agreement with certified concentrations and comparable to the results by homogenization used as reference extraction technique. When the recovery test, performed by spiking the target pesticides into blank samples (5.0 g), was carried out with our optimized MAE conditions, mean recoveries of 16 OP and 10 PYR pesticides were 72-108% for a 1.0 pg spiking level and 70-119% for a 0.2 microg level. These results were acceptable according to the validation guideline for testing method of agricultural chemicals in food by Ministry of Health, Labour, and Welfare in Japan. The results suggested that MAE can be used for the analysis of OP and PYR pesticides in green onions.     

Speciation analysis of selenium enriched green onions (Allium fistulosum) by HPLC-ICP-MS

Green onions (Allium fistulosum) enriched with 10 or 100 μg mL^− 1 Se(IV) or SeMet were analyzed for total selenium and species distribution. Anion and cation exchange chromatographies were applied for the separation of selenium species with mass spectrometric detection. Two different sample preparation methods (NaOH and enzymatic) were compared from the Se extraction efficiency point of view. Total selenium concentration accumulated by the onions reached the 200 μg g^− 1 level expressed for dry weight when applying SeMet at a concentration of 100 μg mL^− 1 as the source of Se. Speciation studies revealed that both in onion bulbs and leaves the predominant form of organic selenium is Se-methyl-selenocysteine (MeSeCys). When Se(IV) was applied for Se-enrichment at a concentration level of 100 μg mL^− 1 both onion leaf and bulb contained a significant amount of inorganic selenium. An unknown compound was also detected.     

The Electrocatalytic Properties of Arc‐MWCNTs and Associated ‘Carbon Onions’

For the first time we report on the electrochemical characteristics of nanometer sized polyhedral graphite onions dispersed amongst arc‐MWCNTs. These are formed during the electric arc discharge method of producing ultrapure MWCNTs (arc‐MWCNTs). The carbon onions are randomly dispersed amongst the arc‐MWCNTs which are produced with very little amorphous carbon deposits or other unwanted impurities and are formed as closed‐ended tubes. By comparison with commercially available open‐ended hollow‐tube multiwalled carbon nanotubes made using the chemical vapor deposition method (cvd‐MWCNTs), a glassy carbon electrode (GCE), an edge‐plane pyrolytic graphite electrode (eppg) and basal plane pyrolytic graphite (bppg) electrode, we can speculate that it is the edge‐plane‐like defect sites that are the electroactive sites responsible for the apparent ‘electrocatalysis’ seen with a wide range of analytes including: ferrocyanide, ruthenium hexaamine(III), nicotinamide adenosine dinucleotide (NADH), epinephrine, norepinephrine, cysteine, and glutathione. The arc‐MWCNTs themselves are produced as closed‐ended tubes with very few, if any, edge‐plane‐like defect sites evident in their HRTEM characterization. Therefore we speculate that it is the carbon onions dispersed amongst the arc‐MWCNTs which have incomplete graphite shells or a rolled‐up ‘Swiss‐roll’ structures that posses the edge‐plane‐like defect sites and are responsible for the observed voltammetric responses. Carbon onions are no more or no less ‘electrocatalytic’ than open‐ended MWCNTs which in turn are no more electrocatalytic than an eppg electrode. As the carbon onions are ubiquitous in MWCNTs formed using the arc‐discharge method the authors advise that caution should be taken before assigning any electrocatalytic behavior to the MWCNTs themselves as any observed electrocatalysis likely arises from the carbon onion impurities.     

Chemie zum Heulen

The IgNobel Prize winners in Chemistry 2013 have impressively proven, that scientific research can indeed make people laugh and then think. Although studies in the field of onion chemistry seem to be funny, the scientific work of the winners brought us closer to a solution of one of the most pressing problems in cookery: the suffering during cutting fresh onions. Therefore, the tremendeous efforts of the Japanese group deserve an IgNobelprize and also our admiration.     

Using combinations of principal component scores from different spectral ranges in near-infrared region to improve discrimination for samples of complex composition

Principal component analysis (PCA) is widely used as an exploratory data analysis tool in the field of vibrational spectroscopy, particularly near-infrared (NIR) spectroscopy. PCA represents original spectral data containing large variables into a few feature-containing variables, or scores. Although multiple spectral ranges can be simultaneously used for PCA, only one series of scores generated by merging the selected spectral ranges is generally used for qualitative analysis. Alternatively, the combined use of an independent series of scores generated from separate spectral ranges has not been exploited.The aim of this study is to evaluate the use of PCA to discriminate between two geographical origins of sesame samples, when scores independently generated from separate spectral ranges are optimally combined. An accurate and rapid analytical method to determine the origin is essentially required for the correct value estimation and proper production distribution. Sesame is chosen in this study because it is difficult to visually discriminate the geographical origins and its composition is highly complex. For this purpose, we collected diffuse reflectance near-infrared (NIR) spectroscopic data from geographically diverse sesame samples over a period of eight years. The discrimination error obtained by applying linear discriminant analysis (LDA) was improved when separate scores from two spectral ranges were optimally combined, compared to the discrimination errors obtained when scores from singly merged two spectral ranges were used.     

Evaluation of analyte stability and method ruggedness in the determination of streptomycin residues in honey by liquid chromatography with post-column derivatization

This study demonstrated that streptomycin in honey is quite stable, and the results showed no obvious differences for 3 samples containing incurred analyte during continuous testing for 4 months. Fifteen laboratories evaluated method performance at 4 fortification levels ranging from 0.010 to 0.100 mg/kg; the recoveries ranged from 73.7 to 78.5%, the reproducibility relative standard deviations ranged from 5.76 to 15.85%, and the repeatability relative standard deviations ranged from 1.64 to 3.80%. In 1999-2002, the method was used to determine streptomycin residues in 5106 lots of honey samples from >20 provinces all over China. All of the honey samples were found to be in conformity with the requirements of customs clearance for exports to Europe, the United States, and Japan. The continuous 4-year quality analysis also found that C18 solid-phase extraction cartridges should be standardized to ensure that the analytical results are accurate when different lots of cartridges are used.     

Analysis of the headspace of foodstuffs near room temperature

Formation of volatiles in onion varieties, aging of coffee, and the quality of birch syrup were studied by using near room temperature headspace GC-MS analysis. Accurate volumes (1–500 mL) of the gaseous samples were introduced into the capillary column either by a syringe or by sucking with a pump. The standard deviation of the contents was typically 1-7% depending on the foodstuff and the compound. The ratio of 2,3-butanedione to 2-methylfuran decreased during the storage of coffee and was a typical measure of aging. Analysis of even the very polar 2,5-dimethyl-4-hydroxy-3(2H)-furanone in the headspace of birch syrup was possible. The distribution patterns of the sulfur-containing volatiles generated by crushed onions were close to each other in different varieties. The rate of the total formation of the compounds varied from cultivar to cultivar.     

Clean recovery of antioxidant flavonoids from onions: Optimising solvent free microwave extraction method

A solvent free microwave hydrodiffusion and gravity extraction (MHG) of flavonol content from onion (Allium cepa L.) was studied. Effectiveness of this innovative method in extraction of onion total phenolic content, total quercetin (TQ), quercetin aglycon (QA), quercetin-3,4′-diglucoside (QDG), quercetin-4′-monoglucoside (Q4G), quercetin-3-monoglucoside (Q3G), kaempferol (KMF) and myricetin (MRT) have been evaluated and compared with conventional solvent extraction. Microwave extraction offers important advantages like shorter extraction time (23 min), cleaner feature (no solvent or water used) and extraction of valuable onion crude juice retaining fresh organoleptic properties with higher phenolic content (58.29 mg GAE/g DW) at optimized power (500 W). Microwave extraction resulted significant yield (81.5%) with 41.9% of flavonol contents, with better retain of remaining flavonoids (55.9%) in residues of onions. QDG (239.7 mg/100 g DW) and Q4G (82.55 mg/100 g DW) have been reported the main flavonol in this study. Minor quantities of QA (traces), Q3G (4.22 mg/100 g DW) and KMF (3.99 mg/100 g DW) were also detected in microwave onion extracts.