Multivariate correlation between color and mineral composition of honeys and by their botanical origin

The mineral content and color characteristics of 77 honey samples were analyzed. Eighteen minerals were quantified for each honey. Multiple linear regression (MLR) was used to establish equations relating the colorimetric CIELAB coordinates to the mineral data. The results obtained shown that lightness (L) was significantly correlated with S, Ca, Fe, As, Pb, and Cd for the dark honey types (avocado, heather, chestnut, and honeydew). For the light and brown honey types (citrus, rosemary, lavender, eucalyptus, and thyme), C(ab) and b showed the lower correlation with the mineral content of the honeys; their regression functions involve a few independent variables (Mg and Al for b and only Al for C(ab)). Furthermore, by means of application of linear discriminant analysis to the mineral content, it was possible to obtain a model that classifies the honeys by their lightness. The prediction ability of the built model, determined with the test set method, was 85%.     

Geographical characterization of polyfloral and acacia honeys by nuclear magnetic resonance and chemometrics

The importance of geographical origin determination is an increasing and pressing requirement for all foods. Honey is one of the largest studied foods due to its nutritional and medicinal properties in a correct diet. In this paper, a total of 41 honey samples (polyfloral and acacia) from different countries have been analyzed in terms of (1)H NMR spectroscopy coupled with multivariate statistical methods. Unsupervised principal component analysis resulted as an efficient tool in distinguishing (1)H NMR spectra of polyfloral and acacia honey samples and for geographical characterization of the latter ones. Hierarchical projection to latent structures discriminant analysis was successfully applied for the discrimination among polyfloral honey samples of different geographical origins. (13)C NMR spectroscopy was applied to honey samples with the aim to investigate possible sugar isoforms differentiation. Our preliminary data indicated a different isoforms ratio between betaFP and betaFF only for polyfloral Argentinean samples, while Hungarian samples showed resonance shifts for some carbons of alphaFF, betaFP, betaFF, and alphaGP isoforms for both varieties. These data confirmed the potentiality of (13)C spectroscopy in food characterization, especially in sugar-based foods.     

Authentication of the botanical origin of honey by near-infrared spectroscopy

Fourier transform near-infrared spectroscopy (FT-NIR) was evaluated for the authentication of eight unifloral and polyfloral honey types (n = 364 samples) previously classified using traditional methods such as chemical, pollen, and sensory analysis. Chemometric evaluation of the spectra was carried out by applying principal component analysis and linear discriminant analysis. The corresponding error rates were calculated according to Bayes' theorem. NIR spectroscopy enabled a reliable discrimination of acacia, chestnut, and fir honeydew honey from the other unifloral and polyfloral honey types studied. The error rates ranged from <0.1 to 6.3% depending on the honey type. NIR proved also to be useful for the classification of blossom and honeydew honeys. The results demonstrate that near-infrared spectrometry is a valuable, rapid, and nondestructive tool for the authentication of the above-mentioned honeys, but not for all varieties studied.     

Identification of botanical biomarkers in Argentinean Diplotaxis honeys: flavonoids and glucosinolates

To select and establish floral biomarkers of the botanical origin of Diplotaxis tenuifolia honeys, the flavonoids and glucosinolates present in bee-deposited nectar collected from hive combs (unripe honey) and mature honey from the same hives fron which the unripe honey samples were collected were analyzed by LC-UV-PAD-ESI-MS(n). Glycosidic conjugates of the flavonols quercetin, kaempferol, and isorhamnetin were detected and characterized in unripe honey. D. tenuifolia mature honeys contained the aglycones kaempferol, quercetin, and isorhamnetin. The differences between the phenolic profiles of mature honey and freshly deposited honey could be due to hydrolytic enzymatic activities. Aliphatic and indole glucososinolates were analyzed in unripe and mature honeys, this being the first report of the detection and characterization of glucosinolates as honey constituents. Moreover, these honey samples contained different amounts of propolis-derived flavonoid aglycones (1765-3171 μg/100 g) and hydroxycinnamic acid derivatives (29-1514 μg/100 g). Propolis flavonoids were already present in the freshly deposited nectar, showing that the incorporation of these compounds to honey occurs at the early steps of honey production. The flavonoids quercetin, kaempferol, and isorhamnetin and the glucosinolates detected in the samples could be used as complementary biomarkers for the determination of the floral origin of Argentinean Diplotaxis honeys.     

Changes in the free amino acid contents of honeys during storage at ambient temperature

This study was carried out to establish the changes in the free amino acid contents of floral honeys, honeydew honeys, and blend honeys during storage at room temperature and to test the capacity of the amino acids to distinguish the origin of the honeys after storage. For this purpose, 54 artisanal honeys (39 floral, 5 honeydew, and 10 blend) were studied. Samples were taken from recently collected honeys and at 3, 6, 9, 12, 16, 20, and 24 months after harvesting. The contents of most of the free amino acids were found to decrease with storage time, with the greatest reduction observed in the first 9 months. The contents of the amino acids aspartic acid, beta-alanine, and proline increased in the first few months after storage, reaching maximum values at 6 months, suggesting the possible existence of enzymatic activities. The application of stepwise discriminant analysis to the free amino acid content data demonstrated that the contents of the amino acids valine, beta-alanine, gamma-aminobutyric acid, serine, isoleucine, alpha-alanine, ornithine, and glutamine correctly assigned 87% of honeys to their group of origin: floral, honeydew, or blend.     

Usefulness of amino acid composition to discriminate between honeydew and floral honeys. Application to honeys from a small geographic area

With the aim of finding methods that could constitute a solid alternative to melissopalynological and physicochemical analyses to determine the botanical origin (floral or honeydew) of honeys, the free amino acid content of 46 honey samples has been determined. The honeys were collected in a small geographic area of approximately 2000 km(2) in central Spain. Twenty-seven honey samples were classified as floral and 19 as honeydew according to their palynological and physicochemical analyses. The resulting data have been subjected to different multivariant analysis techniques. One hundred percent of honey samples have been correctly classified into either the floral or the honeydew groups, according to their content in glutamic acid and tryptophan. It is concluded that free amino acids are good indicators of the botanical origin of honeys, saving time compared with more tedious analyses.     

Authentication of the botanical and geographical origin of honey by mid-infrared spectroscopy

The potential of Fourier transform mid-infrared spectroscopy (FT-MIR) using an attenuated total reflectance (ATR) cell was evaluated for the authentication of 11 unifloral (acacia, alpine rose, chestnut, dandelion, heather, lime, rape, fir honeydew, metcalfa honeydew, oak honeydew) and polyfloral honey types (n = 411 samples) previously classified with traditional methods such as chemical, pollen, and sensory analysis. Chemometric evaluation of the spectra was carried out by applying principal component analysis and linear discriminant analysis, the error rates of the discriminant models being calculated by using Bayes' theorem. The error rates ranged from <0.1% (polyfloral and heather honeys as well as honeydew honeys from metcalfa, oak, and fir) to 8.3% (alpine rose honey) in both jackknife classification and validation, depending on the honey type considered. This study indicates that ATR-MIR spectroscopy is a valuable tool for the authentication of the botanical origin and quality control and may also be useful for the determination of the geographical origin of honey.     

Authentication of the botanical and geographical origin of honey by front-face fluorescence spectroscopy

Front-face fluorescence spectroscopy, directly applied on honey samples, was used for the authentication of 11 unifloral and polyfloral honey types (n = 371 samples) previously classified using traditional methods such as chemical, pollen, and sensory analysis. Excitation spectra (220-400 nm) were recorded with the emission measured at 420 nm. In addition, emission spectra were recorded between 290 and 500 nm (excitation at 270 nm) as well as between 330 and 550 nm (excitation at 310 nm). A total of four different spectral data sets were considered for data analysis. Chemometric evaluation of the spectra included principal component analysis and linear discriminant analysis; the error rates of the discriminant models were calculated by using Bayes' theorem. They ranged from <0.1% (polyfloral and chestnut honeys) to 9.9% (fir honeydew honey) by using single spectral data sets and from <0.1% (metcalfa honeydew, polyfloral, and chestnut honeys) to 7.5% (lime honey) by combining two data sets. This study indicates that front-face fluorescence spectroscopy is a promising technique for the authentication of the botanical origin of honey and may also be useful for the determination of the geographical origin within the same unifloral honey type.     

Immunoreactivity and amino acid content of fermented soybean products

Food allergy has become a public health problem that continues to challenge both the public and the food industry. The objective of this research was the detection and quantification of the major human allergenic soy proteins and to study the reduction in immunoreactivity and improvement of amino acid content after fermentation of soybean flour. Fermentation was carried out in the solid state of cracked seeds inoculated with Aspergillus oryzae, Rhizopus oryzae, and Bacillus subtilis and in the liquid state of milled soybean flours fermented naturally by microorganisms present only in the seeds or by inoculation with Lactobacillus plantarum. ELISA and Western blot were used to quantify IgE antibody response, and HPLC was used to identify and quantify total amino acids. L. plantarum fermented soy flour showed the highest reduction in IgE immunoreactivity (96-99%) depending upon the sensitivity of the plasma used. Among the solid fermented products, the lowest reduction in immunoreactivity was obtained when mold strains, R. oryzae and A. oryzae, were used (66 and 68%, respectively, for human plasma 97.5 kUA/L). Among the solid fermented products, those inoculated with B. subtilis yielded a 81 and 86% reduction in immunoreactivity against both human plasma 97.5 IgE kUA/L and human pooled plasma samples, respectively. When soybean was subjected to liquid fermentation, most of the total amino acids increased significantly ( p < or = 0.05). In solid fermentation with R. oryzae, only Ala and Thr content improved. Fermentation can decrease soy immunoreactivity, and there is potential of developing nutritious hypoallergenic soy products.     

Influence of geographical origin and botanical species on the content of extractives in American, French, and East European oak woods

The chemical composition of East European (Republic of Moldova, Ukraine, and Romania) oaks was investigated profoundly for the first time in the present study and compared with American and French counterparts. Taking into account the high natural variability of oak extractives contents, the wide-ranging sampling was performed for all oak origins: 276 French oaks, 102 East European oaks of both species (Quercus robur L. and Quercus petraea Liebl.), and 56 American oaks (Quercus alba). These oaks were compared with great attention paid to the extractives, which are most important for sensorial impact in wine or spirit maturation, such as ellagitannins and principal odorant substances (aromatic aldehydes, lactones and phenols). The substances in question were studied by application of HPLC and GC-MS techniques. The pattern of all studied extractive contents allowed adequate separation of oak samples according to their geographical origin or botanical species. The highest separation rate was for American and French oaks, whereas East European samples could be partially misclassified in two sets mentioned above. The most important variables for species discrimination were whiskey lactone related variables and ellagitannins, whereas the most important features for distinguishing the origin were eugenol, 2-phenylethanol, vanillin, and syringaldehyde. These substances allowed the distinction of French and East European woods of the same species. With regard to chemical composition, East European wood held the intermediary place between American and French oaks according to their ellagitannin and whiskey lactone levels; nevertheless, it was characterized by specific high values of eugenol, aromatic aldehydes, and 2-phenylethanol.     

Amino acid composition and antioxidant capacity of Spanish honeys

The amino acid composition of 53 honey samples from Spain, consisting of 39 floral, 5 honeydew, and 9 blend honeys, has been determined. Physicochemical characteristics, polyphenolic content, amino acid composition, and estimation of the radical scavenging capacity against the stable free radical DPPH of the honey samples were analyzed. The resulting data have been statistically evaluated. The results showed that pH, acidity, net absorbance, electrical conductivity, and total polyphenolic contents of the honeys showed a strong correlation with the radical scavenging capacity. The correlation between the radical scavenging capacity of honey and amino acid contents was high with 18 of the 20 amino acids detected, with correlation values higher than those obtained for polyphenolic content. These results suggest that the amino acid composition of honey is an indicator of the sample's scavenging capacity.     

Authentication of the botanical origin of honey by front-face fluorescence spectroscopy. A preliminary study

The potential of front-face fluorescence spectroscopy for the authentication of unifloral and polyfloral honey types (n = 57 samples) previously classified using traditional methods such as chemical, pollen, and sensory analysis was evaluated. Emission spectra were recorded between 280 and 480 nm (excit: 250 nm), 305 and 500 nm (excit: 290 nm), and 380 and 600 nm (excit: 373 nm) directly on honey samples. In addition, excitation spectra (290-440 nm) were recorded with the emission measured at 450 nm. A total of four different spectral data sets were considered for data analysis. After normalization of the spectra, chemometric evaluation of the spectral data was carried out using principal component analysis (PCA) and linear discriminant analysis (LDA). The rate of correct classification ranged from 36% to 100% by using single spectral data sets (250, 290, 373, 450 nm) and from 73% to 100% by combining these four data sets. For alpine polyfloral honey and the unifloral varieties investigated (acacia, alpine rose, honeydew, chestnut, and rape), correct classification ranged from 96% to 100%. This preliminary study indicates that front-face fluorescence spectroscopy is a promising technique for the authentication of the botanical origin of honey. It is nondestructive, rapid, easy to use, and inexpensive. The use of additional excitation wavelengths between 320 and 440 nm could increase the correct classification of the less characteristic fluorescent varieties.     

Improved characterization of the botanical origin of sugar by carbon-13 SNIF-NMR applied to ethanol

Until now, no analytical method, not even isotopic ones, had been able to differentiate between sugars coming from C4-metabolism plants (cane, maize, etc.) and some crassulacean acid metabolism plants (e.g., pineapple, agave) because in both cases the isotope distributions of the overall carbon-13/carbon-12 and site-specific deuterium/hydrogen isotope ratios are very similar. Following recent advances in the field of quantitative isotopic carbon-13 NMR measurements, a procedure for the analysis of the positional carbon-13/carbon-12 isotope ratios of ethanol derived from the sugars of pineapples and agave using the site-specific natural isotopic fractionation-nuclear magnetic resonance (SNIF-NMR) method is presented. It is shown that reproducible results can be obtained when appropriate analytical conditions are used. When applied to pineapple juice, this new method demonstrates a unique ability to detect cane and maize sugar, which are major potential adulterants, with a detection limit in the order of 15% of the total sugars, which provides an efficient mean of controlling the authenticity of juices made from this specific fruit. When applied to tequila products, this new method demonstrates a unique ability to unambiguously differentiate authentic 100% agave tequila, as well as misto tequila (made from at least 51% agave), from products made from a larger proportion of cane or maize sugar and therefore not complying with the legal definition of tequila.     

Identification of flavonoid markers for the botanical origin of Eucalyptus honey

European Eucalyptus honeys showed a common and characteristic HPLC profile in which the flavonoids myricetin (3,5,7,3',4', 5'-hexahydroxyflavone), tricetin (5,7,3',4',5'-pentahydroxyflavone), quercetin (3,5,7,3',4'-pentahydroxyflavone), luteolin (5,7,3', 4'-tetrahydroxyflavone), and kaempferol (3,5,7, 4'-tetrahydroxyflavone) were identified. Their contents, and relative amounts, in the analyzed honey samples were quite constant and supported their floral origin. In addition, ellagic acid and the propolis-derived flavonoids pinobanksin, pinocembrin, and chrysin were detected in most samples. The contents of these nonfloral phenolics were much more variable as could be expected for their propolis origin. Myricetin, tricetin, and luteolin had not been identified as floral markers in any other honey sample previously analyzed in our laboratory (chestnut, citrus, rosemary, lavender, acacia, rapeseed, sunflower, heather, lime tree, etc.) or reported in the literature, suggesting that these could be useful markers. Only in some individual heather samples produced in Portugal has tricetin previously been detected in minor amounts. These samples, however, were contaminated with Eucalyptus as revealed by their pollen analysis and the lack of tricetin or their glycosides in heather floral nectar. It remains to be established if myricetin, tricetin, and luteolin originate from Eucalyptus floral nectar where the corresponding glycosides should be present.     

Changes in the free amino acid content of soil following treatment with fungicides

Both quantitative and qualitative changes in the free amino acid content of soil followed treatment with the fungicides Benomyl, Thiram and Verdasan. The amounts of amino acid-N extracted following the additions of high concentrations of the fungicides were in general lower than the controls over the 28-day incubation period. Low rates of application however, resulted in marked increase in the amounts of amino acid-N extracted. A total of nine different amino acids were extracted seven of which were found consistently in the control soils. Glycine and threonine were markedly favoured by all treatments, whereas the frequency of extraction of the other seven amino acids was dependent upon the fungicide used and its concentration. The results are discussed in relation to the changes in the microbiology of soils which are known to be brought about following partial sterilization with fungicides.     

施肥对土壤腐殖质总碳和氨基酸氮含量的影响

采用盆栽试验研究,对比了不施肥、施化肥、施芝麻饼肥、芝麻饼肥+化肥4个处理对烟草根际土壤腐殖质总碳、酸解性氨基酸氮和微生物C、N含量的影响.结果表明,施用饼肥可使土壤腐殖质含量得到一定的提高.施用饼肥可以明显提高土壤中酸解性氨基酸氮含量,与不施肥相比,增幅最大的是中性氨基酸(增加了830 μg/kg)和碱性氨基酸(增加了300 μg/kg),再次是酸性氨基酸(增加了80 μg/kg),而含硫氨基酸含量基本稳定.饼肥与化肥配施可明显提高根际土壤微生物C、N含量,比单施化肥分别提高79.88%～97.14%和29.73%～74.96%.土壤酸解性氨基酸氮与土壤微生物N含量呈极显著的正相关关系,在烟草不同生育期,根际土壤微生物C、N含量动态变化不同,反映出土壤微生物C、N在协调土壤C、N供应方面的重要作用,适量饼肥与化肥配合施用,有利于平衡烟草C、N营养,改善烟叶品质.     

Multielemental analysis and classification of amaranth seeds according to their botanical origin

The characterization of amaranth seeds (Amaranthus spp.) was developed for Amaranthus hypochondriacus, Amaranthus cruentus, and Amaranthus dubius. The elemental concentrations were determined by inductively coupled plasma optic atomic spectroscopy. Pattern recognition methods were used for the characterization of seed samples: nonsupervised methods included principal components analysis and cluster analysis; supervised methods were linear discriminant analysis and partial least squares discriminant analysis (PLS-DA). Informed are the concentrations of the following elements: Ag, Al, Ba, Ca, Co, Cr, Cu, Fe, K, La, Li, Mg, Mn, Mo, Na, Ni, P, S, Sr, V, Zn, and Zr. The lowest mineral content was found in A. hypochondriacus, and the highest one was found in A. dubius. For the classification, selected variables for all multivariate methods were Ba, Cr, Li, Mn, Ni, S, and Sr. Nonsupervised methods allowed us to distinguish between the three species of amaranth; however, PLS-DA supervised methods showed the best prediction ability.     

Sulphur amino acid content and nutritive value of pea and cauliflower crude protein as influenced by Sulphur deficiency

Cystine concentrations (g/16g N) in plant tissue declined more under S deficiency conditions than methionine. In N-balance trials with rats the negative effect of S deficiency on S amino acid composition of peas and cauliflower resulted in a corresponding decrease of the biological value of the protein.     

The use of carbohydrate profiles and chemometrics in the characterization of natural honeys of identical geographical origin

A study of the real possibilities of carbohydrate profiles and chemometrics to characterize the botanical origin of honey from a single geographical area, the Province of Soria (Spain), is presented. To this end, 14 carbohydrates were quantified using high-performance liquid chromatography (HPLC) with pulsed amperometric detection (PAD) in 77 natural honeys, the botanical origins of which were ling, spike lavender, French lavender, thyme, forest, and multifloral. Principal component analysis has been employed as a first approach to characterize the honey samples analyzed, showing similarities between spike lavender and multifloral honeys. The best discrimination among groups is obtained when four canonical discriminant analyses were carried out sequentially, origin by origin, achieving an overall percentage of success of 90% following cross-validation.