Carbohydrate composition of Spanish unifloral honeys

As part of a research project aiming to characterise the most important Spanish floral honeys, the carbohydrate analysis of 109 honey samples was carried out. The main unifloral sources, identified by pollen analysis, were Citrus, heather, Eucalyptus, rosemary, Echium and Rosaceae. A high proportion of multifloral samples were also present.     

Volatile and carbohydrate composition of rare unifloral honeys from Spain

Volatile composition and carbohydrate content of Spanish honey samples from uncommon botanical origins have been studied by gas chromatography coupled to mass spectrometry. About 100 volatile compounds were identified; some of them appeared to be characteristic of particular honey types, such as methyl salycilate in willow (Salix spp.), 2,6,6-trimethyl-2,4-cycloheptadien-1-one (eucarvone) in almond tree (Prunus dulcis) and isophorone in strawberry-tree (Arbutus unedo). Concentration ranges for major carbohydrates were similar to those previously reported in other honeys with different botanical origins, although concentrations of maltulose in avocado honeys (Persea americana) and of melezitose in Quercus ilex honeys were higher. Some carbohydrate alcohols could also be considered as markers of honey botanical origin, such as quercitol for Q. ilex and perseitol for avocado.     

Pattern of pH and electrical conductivity upon honey dilution as a complementary tool for discriminating geographical origin of honeys

Seven physicochemical parameters (water content, ash, water activity, free, lactone and total acidity, pH and electrical conductivity) were analyzed in 19 nectar honeys of different floral origin and from several regions of Argentina. In addition, the pattern of electrical conductivity and pH upon honey dilution were also studied with increasing honey concentration, the pH values decreased exponentially. The dependence of specific electrical conductivity (κ) on honey concentration was characterized by a maximum at a κ value (κ_max) corresponding to a dry solids of honey concentration of 30–35% (w/w). For a given geographical region, ash and acidity values were useful for discriminating honeys of different floral origins. The most adequate parameters for discriminating honeys of different geographical origin were those which described the patterns of pH and electrical conductivity with changes of honey concentration.     

Physico-chemical and bioactive properties of different floral origin honeys from Romania

In this study, we investigated and compared the physico-chemical properties (moisture, colour, ash, and sugars content) as well as total phenols, total flavonoids and antioxidant activity of several honey samples (24) collected from different regions of Romania. The physico-chemical values were in the range of approved limits (conforming to EU legislation); excepting the monosaccharide values for one sample (T2). For this sample, the other values were within legislation limits. The results obtained showed that the most valuable honey is the honeydew one. Correlation between RSA and total phenols and total flavonoids, respectively, was determined, and a positive correlation was found. This study demonstrates remarkable variation in antioxidant properties and content of total phenols in honey, depending on its botanic or geographic source.     

Classification of Italian honeys by mid-infrared diffuse reflectance spectroscopy (DRIFTS)

Diffuse reflectance mid-infrared Fourier transform spectroscopy (DRIFTS) and multivariate statistical analysis methods were used for the identification and classification of honey from different floral sources. The 82 honey samples (robinia, chestnut, citrus, polyfloral) were scanned by DRIFTS in the region 4000–600 cm⁻¹ and also transformed in 1st and 2nd derivatives. Spectral data were analyzed by principal component analysis, general discriminant analysis and classification tree analysis. Classification accuracy near 100% was obtained by discriminant and classification tree analyses. Classification models were successfully validated with one-third leave out method and a classification of about 100% were achieved.     

通电加热中电场强度对猪肉电导率的影响

利用通电加热装置对猪肉进行了通电加热装置,比较了不同电场强度对试样加热速率和电导率的影响,结果显示在其它条件一定的情况下,电场强度越大试样的加热速率就越快;电场强度的不同对试样的电导率略有影响,但影响不大。     

Biological activities and chemical composition of three honeys of different types from Anatolia

In this study, we investigated and compared some chemical properties and in vitro biological activities of three different types of Turkish honey. The first two honey samples were monofloral from chestnut and rhododendron flowers, collected from the east Black Sea region, and the third sample was the heterofloral form of astragalus (Astragalus microcephalus Willd.), thyme (Thymus vulgaris) and other several mountain flowers, collected from Erzincan in Eastern Anatolia. The chemical properties of the honey samples, such as total moisture, ash, total protein, sucrose, invert sugar, diastase activity, hydroxymethylfurfural content and acidity, were determined. Total phenolics, superoxide radical- and peroxynitrite-scavenging activities, and ferric reducing/antioxidant power measurements were used as antioxidant capacity determinants with ±-catechin, butylated hydroxytoluene, ascorbic acid, and trolox^® used as reference. The antimicrobial activity was studied by the agar diffusion method, using eight bacteria and two yeasts. The mineral contents were also determined by an AAS method. The chestnut flower honey had the highest phenolic content, superoxide radical-scavenging activity and reducing power, while the heterofloral honey sample exhibited the highest peroxynitrite-scavenging activity. The antioxidant activities were also found to be related to the sample concentrations. The mineral content of the chestnut honey was much higher than the others. The samples showed moderate antimicrobial activity against some microorganisms, especially Helicobacter pylori ATCC 49503, Staphylococcus aureus ATCC 25923, Bacillus subtilis ATCC 6633, Candida tropicalis ATCC 13803 and Candida albicans ATCC 10231. The honey samples studied proved to be a good source of antioxidants and antimicrobial agents that might serve to protect health and fight against several diseases.     

Mineral content and electrical conductivity of the honeys produced in Northwest Morocco and their contribution to the characterisation of unifloral honeys

In this study the mineral content, ash content and electrical conductivity of 98 honey samples from Northwest Morocco were studied. Using inductively coupled plasma atomic emission spectrometry (ICP‐AES), six minerals were identified and quantified: K, Mg, Mn, Cu, Fe and Zn. Potassium was the predominant mineral (accounting for 80% of the total minerals quantified), followed by Mg and Fe (9 and 3% respectively). The ash content values were lower than 0.6% in 95 of the samples. The higher electrical conductivity values corresponded to the honeydew honeys ( x = 1734 µS cm^?1). In addition, characterisation of the main unifloral honeys by principal component analysis (PCA), linear discriminant analysis (LDA) and multilayer perceptrons (MLP) was carried out. The PCA showed that the cumulative variance was approximately 67%. On the other hand, the LDA and MLP allowed perfect classification of the honeydew (100% correct classification) and Eucalyptus (92%) honeys. © 2003 Society of Chemical Industry     

Determination of the botanical origin of honey by Fourier-transformed infrared spectroscopy: an approach for routine analysis

Fourier-transformed infrared spectroscopy has been established for analysing most of the physical–chemical parameters of honey. Additionally this technique can be used for determination of the botanical origin of a honey sample by comparison of the mid-infrared spectra. In this study calibrations for authentification of the main regional honey types should be developed to be able to measure simultaneously physical–chemical properties and the botanical origin at a minimum of time and at low costs. Honey samples from local beekeepers were collected and characterized by standard methods. The most common honey types were used for calibration. We recorded the mid infrared spectrum from each honey sample. Classification models were achieved by PCA-calibration and validated with samples from various botanical origins. Honey of Brassica spp., Robinia pseudoacacia, Calluna vulgaris, Trifolium spp., Tilia spp., Helianthus annuus, Centaurea cyanus and honeydew honey was used for calibration. Afterwards the calibration models were improved during routine analysis. Most of the honey samples from rape, false acacia, heather and honeydew can be classified correctly by the FTIR in consideration of the physical–chemical and sensorial properties.     

Evolution of acid phosphatase activity of honeys from different climates

Acid phosphatase is an enzyme of honey whose values have been related to honey’s fermentation. In this work, we have studied the evolution, throughout thirty months, of acid phosphatase activity on honey samples originating in continental and oceanic areas. We have also researched the influence of induced granulation and pH on acid phosphatase activity evolution. Acid phosphatase activity has been determined by measuring, at 400 nm, 4-nitrophenol formed after the hydrolysis, at acid pH, of 4-nitrophenylphosphate in the presence of acid phosphatase. From the start, acid phosphatase activities have been higher in honeys from oceanic climate. Similar trends of evolution of acid phosphatase activity have been found in both honeys from continental and oceanic climates. In the end of the study, 100% samples showed a decrease of acid phosphatase activity. Induced granulation does not modify the trend of acid phosphatase activity evolution, although this technological process has an influence on the time at which changes within the evolution occurs. pH of samples has demonstrated to have a strong influence on the activity of acid phosphatase, so that the higher the pH, the lower the decrease of acid phosphatase activity. In honeys originated from continental climate area, pH and acid phosphatase activity have been correlated throughout the study.     

Interest of on-line monitoring electrical conductivity during wine fermentation

Under wine-making conditions, alcoholic fermentations are carried out without on-line monitoring due to the lack of robust, precise and cheap sensors. We describe the interest of on-line monitoring electrical conductivity and his good correlation with pH during fermentation. The change in conductivity is primarily due to the assimilation of nitrogen (in particular, ammoniacal nitrogen), which is usually the limiting nutrient of the fermentation kinetics. The limits of conductivity measurement to follow the nitrogen assimilation were discussed with the variability observed with five different grape musts.     

Microbiological and chemical characterization of honeys from central Argentina

The characterization of some honey samples from southern Córdoba (Argentina) was carried out on the basis of their microbiological (Clostridium, fungi and yeasts), physical (colour) and chemical (carbohydrates, HMF, water and free acidity) analysis. The results showed that honeys produced in this region are of good quality. HMF content and free acidity values were mostly low, indicating honey freshness. Most of the samples contained less than 20% water. Glucose and fructose accounted for more than 60% of the weight. The amount of yeast and fungi found in the honey samples was less than 1 × 10² CFU/g. Low quantities of vegetative cells and spores of Clostridia were found in some honey samples. A standardization and a rationalization of beekeeping techniques throughout southern Córdoba may further improve honey quality, and ensure it over the years.     

Classification of the floral origin of Uruguayan honeys by chemical and physical characteristics combined with chemometrics

This study reports both the chemical and physical characterization of honey samples produced in Uruguay and the classification of honeys by floral origin using chemometrics. Moisture (M), pH, electric conductivity (EC), hydroxymethyl-2-furaldehyde and colour composition were analysed. As well as composition, classification of honey samples from different floral origins namely pasture (n=6), Eucalyptus spp. (n=6), Citrus spp. (n=5), Baccharis spp. (n=5), multifloral (n=2) and others (n=6) was attempted using principal component analysis and linear discriminant analysis. All the honey samples were found to meet the international specifications for the chemical parameters evaluated. The EC, M and pH were the variables that explain the classification of honey samples according to floral origin. More than 80% of the samples belonging to pasture, Citrus spp. and Baccharis spp. honeys were correctly classified according to its floral origin. Further studies are needed in order to investigate the effect of other floral and geographical (region) to provide a robust model to classify honey samples.     

The effects of concentration on electrical conductivity of orange juice concentrates during ohmic heating

Ohmic heating is an alternative heating technique, using an electrical current passing through the food product. It can be specially used in pumpable food lines as an alternative heating unit. In this study, orange juice concentrates having 0.20–0.60 mass fraction soluble solids were ohmically heated by using five different voltage gradients (20–60 V/cm). The dependence of electrical conductivity on temperature, voltage gradient and concentration were measured. The ohmic heating system performance coefficients were calculated by using the energies given to the system and taken by the orange juice samples. The mathematical model results, taking system performance coefficients into account, were compared with experimental ones. The predictions of the mathematical model were found to be very accurate.     

Classification of Chinese honeys according to their floral origin by near infrared spectroscopy

The feasibility of near infrared (NIR) spectroscopy and multivariate analysis as tools to classify Chinese honey samples according to their different floral origins was explored. Five kinds of honey, namely, acacia, linden, rape, vitex and jujube, were analysed using a NIR spectrophotometer with a fibre optic probe. Classification models based on the NIR spectra were developed using Mahalanobis-distance discriminant analysis (MD-DA) and a back propagation artificial neural network (BP-ANN). By the MD-DA model, total correct classification rates of 87.4% and 85.3% were observed for the calibration and validation samples, respectively, while the ANN model resulted in total correct classification rates of 90.9% and 89.3% for the calibration and validation sets, respectively. By ANN, the respective correct classification rates of linden, acacia, vitex, rape and jujube were 97.1%, 94.3%, 80.0%, 97.1%, and 85.7% in calibration, and 100%, 93.3%, 80.0%, 100%, and 73.3% in validation. The results indicated that NIR combined with a classification technique could be a suitable technology for the classification of Chinese honeys from different botanical origins.     

Differentiation of monofloral citrus,rosemary, eucalyptus,lavender, thyme and heather honeys based on volatile composition and sensory descriptive analysis

The volatile profiles of 49 Spanish honey samples of different botanical origins were obtained by means of gas chromatography–mass spectrometry and sensory analysis. Citrus honeys were characterised by higher amounts of linalool derivatives, limonyl alcohol, sinensal isomers, and α-4-dimethyl-3-cyclohexene-1-acetaldehyde, together with fresh fruit and citric aromas; eucalyptus honeys had hydroxyketones (acetoin, 5-hydroxy-2,7-dimethyl-4-octanone), p-cymene derivatives, 3-caren-2-ol and spathulenol, cheese and hay aromas; lavender honeys had hexanal, nerolidol oxide, coumarin, important concentrations of hexanol and hotrienol and sensorial attributes, including balsamic and aromatic herb aromas; finally, heather honeys were characterised by high contents of benzene and phenolic compounds and ripe fruit and spicy aromas. Some of these compounds and sensory attributes were only found in honeys from a specific floral source and could thus be of interest for use as markers of their botanical origin.     

Classification of monofloral honeys from different floral origins and geographical origins based on rheometer

A rheometer was used to classify commercial honeys. Five kinds of Yichun honeys from different floral origins and five kinds of Acacia honeys from different geographical origins were classified based on a rheometer by four pattern recognition techniques: Principal Component Analysis (PCA), Cluster Analysis (CA), Partial Least Squares (PLS), and Support Vector Machines (SVM). All the samples for different floral origins or different geographical origins were demarcated clearly by PCA, PLS. The samples from different floral origins could be classified by SVM, and the samples from different geographical origins also have a high correct classification rate (97.5%). The classification rates for different floral origins and geographical origins were 95% and 97.50% by CA, respectively. Three regression models: Principal Component Regression Analysis (PCR), Partial Least Squares Regression (PLSR), Support Vector Regression (SVR) were used for category forecast. The regression analysis showed that SVR with radial basis function kernel worked most effective.     

Major flavonoids of Argentinean honeys. Optimisation of the extraction method and analysis of their content in relationship to the geographical source of honeys

In the present research we optimised an extraction procedure for the flavonoid aglycones: myricetin, quercetin and luteolin from honeys (as natural biological matrices), based on Amberlite XAD-4 resin followed by HPLC quantification. In addition, honeys from three geographical regions of Argentina were analysed with regard to the contents of these flavonoids. The extraction procedure was optimised for XAD-4 resin considering: resin/honey ratio, elution volume to desorb flavonoids and colour intensity of honeys. Differences in flavonoid recoveries were observed depending on the colour intensity. The flavonoid aglycones contents, in accordance with differences in geochemical characteristics and typical vegetation, varied with the geographical origin of honeys. The results obtained allowed us to consider these three flavonoids as chemical markers for the phytogeographical origin of honeys. In the case of monofloral honeys, the contribution of each one of the flavonoids was associated with the presence of a dominant pollen kind in these samples.     

Flavonoids in Meliponinae honeys from Venezuela related to their botanical, geographical and entomological origin to assess their putative anticataract activity

 Honey was collected from 24 stinglessbee nests in Venezuela. The flavonoid compounds in the phenolic extracts were analysed and related to the botanical, geographical and entomological origin of the honey. Honeys produced in savannas were richer in flavonoids compared with honeys from the forests. It was found that phenolic extracts of honey of the same geographical origin had similar flavonoid profiles, whereas the same could not be said of honeys of the same entomological origin, although the botanical origin of the samples was variable. It is proposed that analysis of stinglessbee honey eyedrops in terms of their flavonoid content can be used as a basis of authenticating and controlling for their geographical origin. Received: 28 July 1997