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     

Physicochemical properties and pollen spectrum of imported and local samples of blossom honey from the Pakistani market

Fifteen samples of different geographical origin including Pakistan were analysed for density, ash, water content, electrical conductivity, total acidity, pH, total solid, hydroxylmethylfurfural (HMF), minerals and trace metals. The physicochemical parameters were found to be within acceptable ranges (specific gravity 1.40–1.46, ash 0.03–0.21%, moisture 15.6–19.2, total solid 78.7–81.4%, free acidity 23.55–58.52 meq kg^?1, conductivity 0.27–0.37 mS cm^?1, pH 3.29–4.05, viscosity 33.4–136.4 poise). However, the analysis of HMF showed that imported samples were either exposed to a high temperature during processing or were overage. Greater attention is required, therefore, in the analysis of HMF and in deciding the shelf life, particularly for the imported samples before marketing. Pollen analysis revealed that all the analysed samples were of a multifloral type. All the data were statistically tested using principal component analysis (PCA) with the aim of characterizing the honeys and identifying the most significant parameters in the analysed samples.     

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.     

Jujube Honey from China: Physicochemical Characteristics and Mineral Contents

We investigated and compared the physicochemical properties (moisture, color, ash, pH, electrical conductivity, free acidity, lactonic acidity, total acidity, fructose, glucose, sucrose, diastase activity, and HMF) and mineral contents (Al, Ca, Co, Cr, Cu, Fe, K, Li, Mg, Mn, Na, Ni, As, Cd, Pb, and Zn), as well as total proline and total protein contents of 23 jujube honey samples collected from different regions of China. The mineral content was determined by inductively coupled plasma‐optical emission spectrometry (ICP‐OES). The physicochemical values were in the range of approved limits (conforming to EU legislation) in all 23 samples. The physicochemical properties of jujube honey showed significant variations among samples. The mean pH value of the jujube honeys was 6.71. The most abundant minerals were potassium, calcium, sodium, and magnesium, ranging between 1081.4 and 2642.9, 97.1 and 194.2, 7.79 and 127.8, and 10.36 and 24.67 mg/kg, respectively, and potassium made up 71% of the total mineral content. This study demonstrated remarkable variation in physicochemical parameters and mineral contents of jujube honey, mainly depending on its geographic source.     

Multi-elemental composition and physical properties of honey samples from Malaysia

The elemental profiles of six honey samples from Malaysia had been constructed using the data obtained from both ICP-AES and ICP-MS. Potassium and sodium were the most abundant minerals covering from 69.3-78.6% and 14.1-28.7%, respectively. The ratio of potassium to sodium was more than one. Even though the minerals and trace elements composition varied dependent on the type of honey samples, there was no statistically significant difference between the analysed honey samples, namely tualang, gelam, acacia and a few forest honeys based on two-factor ANOVA and cluster analysis. The total element content of honey samples were strongly correlated with the electrical conductivity, but only have moderate correlation with the ash content and honey colour based on the regression analysis. PCA result on the available elemental data from worldwide honeys, including honey samples from Malaysia revealed that potassium and sodium were the mineral markers to distinguish honey origin. Both tualang and gelam honey samples from Malaysia have close mineral profile with sesame honeys from Egypt and multifloral honeys from India, whereas forest honeys Malaysia were near to avocado honeys from Spain and multifloral honeys from India.     

Characterisation of Slovenian honeys on the basis of sensory and physicochemical analysis with a chemometric approach

The purpose of this study was sensory and physicochemical characterisation of Slovenian honeys with a chemometric approach. Honey samples were obtained from the beekeepers in different natural geographical macroregions of Slovenia. The sensory characteristics of the seven main types of Slovenian honeys are described, together with the physicochemical analyses. The average results of electrical conductivity (0.19–1.61 mS cm^?1), pH (4.01–5.51), free acidity (13.3–30.9 meq kg^?1), proline content (317–558 mg kg^?1), protein content (1.70–3.53 g kg^?1), optical rotation (–19.6 to 12.6), phenolic content (44.9–232.5 mg GAE kg^?1) and antioxidant activity [69.6–456.4 μm Fe(II)] show wide variability among analysed honey types. Statistically significant differences were obtained among different honey types, generally lower values of the analysed parameters were determined in the light honeys, as the acacia, linden and multifloral honeys, while the higher values are characteristic for darker honeys, as the chestnut, fir, spruce and forest honeys. Linear discriminant analysis was performed to classify the honey samples according to their botanical origin and proved that physicochemical parameters analysed can provide enough information for the classification and distinction of acacia, linden, multifloral and chestnut honeys, and the group of honeydew honeys (fir, spruce and forest honeys).     

Sugar profile and physicochemical properties of Ethiopian monofloral honey

Three hundred twenty honey samples were collected from Ethiopia, and categorized into nine monofloral honeys using melissopalynology. Theses monofloral honeys were investigated for their sugar profile, physicochemical properties, and quality of honeys. Sugars (fructose, glucose, sucrose, maltose, turanose, and isomaltose) were identified using high-performance liquid chromatography and physicochemical properties (moisture, water activity, pH, acidity, ash, minerals, conductivity, colour) using the Harmonized Method of the International Honey Commission. Moisture and water activity showed a strong regression coefficient (r² = 0.92). Moisture content alone did not sufficiently describe the quality of honey during storage and processing.     

Antioxidant capacity of Spanish honeys and its correlation with polyphenol content and other physicochemical properties

Thirty‐six Spanish honeys of different floral origins (nectars and honeydews) were assessed to estimate their radical‐scavenging capacity against the stable free radical DPPH (1,1‐diphenyl‐2‐picrylhydrazyl), their ability to inhibit enzymatic browning in apple homogenate and their clarifying effect on apple juice. These capacities were evaluated spectrophotometrically. Physicochemical parameters such as pH, acidity, net absorbance, electrical conductivity and total polyphenol content of the samples were also evaluated. It was observed that all these parameters presented a strong correlation with radical‐scavenging capacity, whereas antibrowning capacity had a low correlation with conductivity and no correlation with honey pH. When data of nectar and honeydew honeys were evaluated separately, net absorbance and honey acidity seemed to be good parameters to evaluate the antioxidant activity of nectar honeys; however, in honeydew honeys there were only relationships between radical‐scavenging activity and honey conductivity and between browning inhibition of homogenates and total acidity. In general, honeydew honeys showed higher antioxidant capacities than nectar honeys. Copyright © 2007 Society of Chemical Industry     

Palynological and physicochemical data characterisation of honeys produced in the Entre‐Douro e Minho region of Portugal

Honey legislation has been addressed to establish the minimum marketing level of the product and the need for consumer protection through correct denominations. Research oriented toward assessment of floral origin and physicochemical properties may increase the commercial value of these products. The characteristics of thirty‐one honeys produced in the Entre‐Douro e Minho region in Portugal were studied. Pollen features and some physicochemical parameters (moisture, ash, pH, free acidity, electrical conductivity, hydroxymethylfurfural contain, apparent sucrose, reducing sugars and diastase activity) were determined. The samples were found to meet international honey specifications. The present study found a linear regression between the ash content of honeys and their specific conductivity. Five samples are listed as Eucalyptus honey, one sample as Citrus honey, and twenty‐five samples as multifloral honeys. Of the total, 87.1% exceeded the quality parameters and should be labelled as ‘virgin’ honey.     

Characterisation of Serbian unifloral honeys according to their physicochemical parameters

The characterisation of three unifloral Serbian honeys (acacia, sunflower and linden) was carried out based on some common physicochemical parameters (water content, electrical conductivity, free acidity, optical rotation and pH). A total of 201 honey samples, collected during the 2009 harvesting season, were analysed. Principal component analysis (PCA) and linear discriminant analysis (LDA) were used to highlight the data structure and to find the relationships between the physicochemical parameters and the botanical origin of honey. The variables that best discriminated the samples were electrical conductivity (ranging from 0.10 to 0.76 mS/cm), free acidity (ranging from 7.80 to 42.70 meq/kg) and pH (ranging from 3.17 to 5.85). LDA resulted in a classification model with a high predictive power, allowing further assessment of unknown samples of the three unifloral honeys. Determination of geographic origin of acacia honey samples based on physicochemical properties and chemometrics was attempted.     

Unifloral honeys of the province of Buenos Aires,Argentine

Samples of 63 unifloral honeys of the province of Buenos Aires, Argentina, from Eucalyptus spp, Lotus spp, Helianthus annuus, Melilotus albus, Brassicaceae, clovers other than Lotus and Melilotus, and Sagittaria montevidensis, were obtained by cold extraction at the laboratory. The frequencies of occurrence of pollen types, and the moisture, hydroxymethylfurfural, ash, acidity and proline contents were determined. Electrical conductivity, pH and colour were also analysed. Honey presented a high percentage (about 40%) of unifloral honey. The most frequent unifloral honeys were from Eucalyptus spp, Lotus spp and Helianthus annuus. Samples had a low pollen diversity with six to 19 pollen types, the most important nectariferous taxa being those that characterized the unifloral honeys. All samples presented moisture, hydroxymethylfurfural, ash and free acidity contents according to international standards. The colour of the honey was from water white to light amber, and all samples had a very low ash content. Significant differences at the 5% level in the hydroxymethylfurfural content, electrical conductivity, colour and proline content were observed among honeys from different floral origins. However, a high variability between samples from the same floral origin was observed, indicating that other factors such as accompanying pollen and geographical origin affect the physicochemical characteristics of honey. Copyright © 2005 Society of Chemical Industry     

Aroma profile and physico‐chemical properties of artisanal honey from Tabasco,Mexico

The aim of this work was to characterise, physico‐chemically, sugar composition and aroma profile of ten honey samples collected by small producers during two seasons and produced in different agricultural ecosystems from Tabasco State (Mexico). The mean values obtained for the physico‐chemical parameters were: pH 3.63; 19.25% moisture; 78.8°Brix sugar; 0.64% ash; 0.25 mS cm^?1 electrical conductivity and 0.58 water activity. Based on colour parameters, Tabasco honeys can be placed in the group of dark honeys. In the analysed samples; fructose was the major sugar (39.45%), followed by glucose (35.74%) while sucrose only represented 2.93%. The volatile profiles of the ten honey samples were obtained by gas chromatography‐mass spectrometry. All the honeys were characterised by their high contents of benzene and furan‐related compounds. As a result, artisanal honeys from Tabasco (Mexico) can be considered to present a good level of quality.     

Physicochemical attributes and pollen spectrum of Portuguese heather honeys

The qualities of selected honey samples of “Serra da Lousã” (Portugal) from three consecutive harvests (20 samples from each harvest) were evaluated by determing the pollen spectrum and physicochemical attributes. The following determinations were carried out: moisture, electrical conductivity, hydroxymethylfurfural, diastase activity, pH, acidity (free, lactone and total), formol number, reducing sugars, apparent sucrose, insoluble material and ash. The samples were found to meet all major national and international honey specifications. Honeys were considered to be monofloral whenever the dominant pollen was found to be over 45% of total pollen. From the 60 studied samples, 70% were monofloral honeys from Erica sp., 17% monofloral honeys from Ericaceae (Erica sp. and Calluna vulgaris (L.) Hull) and 13% multifloral honeys with a high percentage of Erica sp.     

Effect of inverted saccharose on some properties of honey

In this study, three groups of honey [natural honey; honey produced by the supplementary feeding of bees with saccharose syrup (SSH) and heat and acid (88 °C, 2 h; 0.1% HCl) treated saccharose syrup honey (ISSH)] were produced and physicochemical (water content, pH, free acidity, ash, HMF, diastase activity, sucrose, protein and viscosity), microbiological and sensory properties of these honeys were determined. Also, mineral contents of the honeys were measured. Moisture and ash contents of SSH were higher, acidity level was lower than those of other honeys. The mineral content of natural honey was higher than that of the others, except for Pb and Zn. Diastase activity of ISSH was below the standard limit and HMF content of this honey was high, but not exceeding the limit. Supplementary feeding of honey bees with inverted (acid and heat treatment) saccharose yielded a honey which had a higher HMF content and a lower diastase activity, moisture content and free acidity than natural honey or SSH.     

Characterization and classification of Thymus capitatus (L.) honey according to geographical origin based on volatile compounds,physicochemical parameters and chemometrics

Greek thyme honeys (Thymus capitatus L.) were characterized and classified according to geographical origin based on the determination of volatile compounds and physicochemical parameters using MANOVA and Linear Discriminant Analysis. Forty two thyme honey samples were collected during the harvesting period in 2011 from 5 different regions in Greece known to produce thyme honey of good quality. The analysis of volatile compounds was performed by Headspace Solid Phase Microextraction coupled to Gas chromatography/Mass spectroscopy. Forty seven volatile compounds were identified and semi-quantified. Physicochemical analysis included the determination of pH, free, lactonic and total acidity, electrical conductivity, moisture, ash, lactonic/free acidity ratio and color parameters: L*, a*, b*. Using 9 volatile compounds and 11 physicochemical parameters the honey samples were satisfactorily classified according to geographical origin using volatile compounds (64.3% correct prediction), physicochemical parameters (92.7% correct prediction), and the combination of both (92.9% correct prediction).     

Floral authentication of Greek unifloral honeys based on the combination of phenolic compounds,physicochemical parameters and chemometrics

Greek unifloral honeys (pine, thyme, fir, orange blossom) were characterized and classified according to botanical origin based on phenolic compound content and conventional physicochemical parameters using MANOVA and Linear Discriminant Analysis. One hundred and nineteen honey samples were collected during the harvesting period 2011 from 14 different regions in Greece known to produce unifloral honey of good quality. The analysis of phenolic compounds quercetin (3,5,7,3′,4′-pentahydroxyflavone), myricetin (3,5,7,3′,4′,5′-hexahydroxyflavone), kaempferol (3,5,7,4′-tetrahydroxyflavone), chrysin (5,7-dihydroxyflavanone), and syringic acid (4-hydroxy-3,5-dimethoxybenzoic acid), was performed by high pressure liquid chromatography. Conventional quality parameter analysis included the determination of: pH, free, lactonic and total acidity, electrical conductivity, moisture, ash, as well as lactonic/free acidity ratio and colour parameters L*, a*, and b*. Using 4 phenolic compounds and 10 conventional quality parameters honey samples were satisfactorily classified (96.6% correct prediction) according to botanical origin.     

Pollen spectrum and physico‐chemical attributes of heather (Erica sp.) honeys of north Portugal

BACKGROUND: Honey legislation has been addressed to establish the minimum marketing level of the product and the need for consumer protection through correct denominations. Research oriented toward assessment of floral origin and physico‐chemical properties may increase the commercial value of these products. The characteristics of 23 unifloral honeys of Erica sp., from Portugal, were studied. Pollen features and some physicochemical parameters (moisture, ash, pH, free acidity, electrical conductivity, hydroxymethylfurfural content, apparent sucrose, reducing sugars and diastase activity) were determined. RESULTS: All honey samples can be classified as monofloral Erica sp., they gave a mean value of 56% of Erica pollen type. The families Fabaceae and Rosaceae provided the greatest number of pollen types with 8 and 4 pollen types each respectively. The second most important pollen type is Eucalyptus, present in 69.6% of the samples. All honey samples met the international physicochemical quality standards. The present study found a linear correlation (R = 0.996) between the ash content of honeys and their specific conductivity. CONCLUSION: All honey samples can be classified as monofloral Erica sp. Unifloral honeys are increasingly requested and appreciated, despite their higher prices. The samples were found to meet all major international honey specifications. Copyright © 2009 Society of Chemical Industry     

Palynological,physico‐chemical and organoleptic characteristics of carob tree (Ceratonia siliqua L.) honey from Sicily

This study shows the results of melissopalynological and sensory evaluations on twenty‐five carob tree honey samples coming from Sicily and declared unifloral by the local beekeepers. This specific carob tree honey production is erratic and limited because of its cold weather spreading, depending on seasonal trends that influence both the final amount and quality of honey itself. According to the melissopalynological results on samples, a minimum of 15% carob tree pollen was considered sufficient to typify these honeys as unifloral. The physico‐chemical analysis was performed on the samples satisfying this percentage and determined the following parameters: moisture, pH, acidity, HMF, diastase activity, electrical conductivity, ash, sugar and colour. Physico‐chemical analyses showed medium to high values for diastase activity, electrical conductivity, free acidity and moisture.     

Quality of honeys influenced by thermal treatment

Honey producers have been heating honeys at mild temperatures below 100 °C chiefly in order to prevent post-bottling crystallization. In this study, we aimed to determine the effects of thermal treatment on the HMF content of honeydew and floral honey during the isothermal heating process at mild temperatures. Water content, formol number, total acidity, pH value and minerals were also determined in both honey types as their characteristics differ with composition, which is able to affect the rate of HMF formation. Potassium content and pH value were found as the distinguishing properties and both were greater in honeydew honey than in floral honey (p<0.01). Honeydew and floral honey samples were heated at 75, 90 and 100 °C for 15-90 min and analysed for HMF content by HPLC-RP. The Arrhenius model was used to calculate reaction rate constants and activation energies which were found to be different for each of the honey types. Heating at 90 °C for up to 90 min in floral honeys and up to 75 min in honeydew honeys did not cause a significant increase of HMF and not exceed the threshold level of 40 mg kg⁻¹. Our results show that the excessive HMF content might be related to primitive storage conditions rather than overheating.     

Differentiation of Greek Thyme Honeys According to Geographical Origin Based on the Combination of Phenolic Compounds and Conventional Quality Parameters Using Chemometrics

The aim of the present study was to differentiate Greek thyme honeys according to geographical origin, based on phenolic compound content and conventional physicochemical parameters using MANOVA and Linear Discriminant Analysis. Thirty-five thyme honey samples were collected during the harvesting period 2011 from four different regions in Greece (Irakleio, Hania, Kefalonia and Lakonia) known to produce thyme honey of good quality. The analysis of phenolic compounds (quercetin, myricetin, kaempferol, chrysin, and syringic acid) was performed by high pressure liquid chromatography. Conventional quality parameter analysis included the determination of the following: pH, free, lactonic and total acidity, electrical conductivity, moisture, ash, as well as lactonic/free acidity ratio and colour parameters L*, a*, b*. Using five phenolic compounds and 11 conventional quality parameters, thyme honey samples were satisfactorily classified (91.2 % correct prediction) according to geographical origin.