A review of volatile analytical methods for determining the botanical origin of honey

Aroma is an important quality factor in foods. The aroma of bee honey depends on volatile fraction composition, which is influenced by nectar composition and floral origin. Honey of unifloral origin usually commands higher commercial value, thus the floral determination and certification of unifloral honey plays an important role in quality control. This review concerns investigations made on the volatile fraction of bee honey by gas chromatography/mass spectrometry. Recent advances in extraction methods, results achieved, and comparisons of alternative dependable methods for determining floral origin of bee honey are discussed. We emphasize solid phase micro-extraction gas chromatography (SPME/GC) methodology and present some of the results obtained to date, plus the advantages and drawbacks of SPME/GS in comparison with other methods.     

Some aspects of dynamic headspace analysis of volatile components in honey

Purge and Trap (P&T) has been evaluated as a fractionation technique for the GC–MS analysis of the most volatile compounds in honey. The volatile fraction of twenty-two commercial honeys of eight different botanical sources (eucalyptus, thyme, citrus, rosemary, heather, lavender, multiflower and honeydew) was characterized by P&T–GC–MS. Hundred volatile compounds were characterized, 18 of them being determined for the first time in honey. Compounds detected included volatiles derived from the floral nectar or honeydew source such as terpenes, furan derivatives from honey processing and storage and other compounds whose origin could be related to microbial or environmental contamination. This method has also been validated with regard to data reproducibility; with relative data (percentage of total volatile composition) showing a better precision over quantitative results calculated using an internal standard. Application of multivariate statistical analysis to P&T–GC–MS data has shown to be very promising to classify samples according to their botanical origin.     

Comparison of volatile compounds in yoghurts made from cows’, buffaloes’, ewes’ and goats’ milks

The composition of the volatile fraction of yoghurts made from cows’, buffaloes’, ewes’ and goats’ milks was investigated during the 28 days of storage at 4 °C using solid‐phase microextraction technique (SPME) and gas chromatography coupled to mass spectrometry analysis (GC/MS). A total of 34 volatile compounds were identified in yoghurts during their storage at 4 °C, including aldehydes, ketones, alcohols, esters, acids, terpenes, hydrocarbons and sulphur compounds. In this study, acetaldehyde, diacetyl and acetoin, considered as the major compounds of yoghurt, were detected in all yoghurts.     

Effect of pork fat addition on the volatile compounds of foal dry-cured sausage

The effect of fat content on volatile compounds from foal dry-cured sausage was studied. Three batches (10 units per batch) of dry fermented sausages with different pork back fat content (5%, 10% and 20%) were manufactured; low fat (LF), medium fat (MF) and high fat (HF), respectively. A total of 45 volatile compounds were extracted by purge-and-trap and identified by GC-MS in the headspace of the batches. The mixture comprised 11 terpenes, 15 esters, 14 hydrocarbons and 2 alcohols. Spices were responsible for the generation of 14 volatile compounds comprising terpenes and hydrocarbons. After 49 days of ripening volatile compounds from spices represented 52.9, 38.9 and 31.2% of the total area for samples from LF, MF and HF batches, respectively, while lipid autooxidation was responsible for the generation of 8 volatile compounds. The PCA offered a good separation of the mean samples according to their fat content.     

Contribution of enterococci to the volatile profile of slightly-fermented sausages

The volatile profiles of slightly-fermented sausages inoculated with eight different enterococci strains were determined and compared with a fermented sausage manufactured without any inoculation. The volatile profile was determined by solid-phase microextraction (SPME) and gas chromatography coupled to mass spectrometry (GC/MS). A total of 121 volatile and semi-volatile compounds were identified in the samples of the final products (day 21). Terpenes from spices added during manufacture of dry-fermented sausages were the main group of compounds in the volatile profile. Other groups included alcohols (18% of total volatile compounds), aldehydes (16%), alkanes and alkenes (12%), and ketones (10%). These are derived from lipids, proteins or carbohydrates and formed during fermentation and ripening. In terms of global volatile composition, the batches inoculated with enterococci strains were similar to those obtained for non-inoculated batch. However, some quantitative differences in the volatile profiles of different batches were found, mainly in the compounds formed from amino acid catabolism (i.e.: propanol, isoamyl), from free fatty acid oxidation (i.e.: hexanal, hexanol), or from carbohydrate fermentation (i.e.: 2-butanone, acetoin). In comparison with non-inoculated sausages, some batches were more resistant to oxidation; they contained fewer volatile compounds arising from lipid oxidation. The use of different selected enterococci strains did not alter the volatile profile of slightly-fermented sausages. The enterococci strains provide similar volatile compounds to those usually reported in the literature.     

GC/MS法分析烟用接装纸中挥发性有机化合物

建立了顶空-气质联用(HS-GC/MS)法,对烟用接装纸中挥发性有机化合物(VOCs)残留量进行测试.结果表明:(1)该方法检测限为0.001-0.004 mg/mL,回收率为89.35％- 108.96％,相对标准偏差(RSD)＜4％;(2)所有52个被检烟用接装纸榉品均为合格样品,所有样品中均未检出苯、乙苯、二甲苯、乙酸异丙酯、丁酮,YC171-2009《烟用接装纸》标准中规定的5种VOCs成分中只有乙酸正丁酯有个别检出;(3)醇类检出率较高,其中所有样品都有乙醇检出,异丙醇、正丁醇的检出率也比较高;(4)丙二醇甲醚有较高的检出率,且其检出量相对较大.研究结果充分说明,该方法适合于烟用接装纸中VOCs的快速批量检测.     

A potentiometric electronic tongue for the discrimination of honey according to the botanical origin. Comparison with traditional methodologies: Physicochemical parameters and volatile profile

The effectiveness of a potentiometric electronic tongue, made of various metals and metallic compounds was evaluated for the differentiation of honey in three different states: raw, liquefied and pasteurized. Principal component analysis (PCA) and a neural network showed that potentiometric electrodes seem useful to classify honey by its botanical origin, though they do not seem capable of discrimination between applied thermal treatments. The same was observed in the samples for physicochemical parameters and volatile compounds analysed with PCA. Au, Cu and Ag electrodes were more decisive in the discrimination of honey. A remarkable correlation (PLS analysis) between the electronic tongue and the physicochemical parameters was found, the best results being for color Pfund (r² = 0.958), L^∗ (r² = 0.935) and diastase activity (r² = 0.926). The correlation with volatile compounds was much weaker, though this improved for specific characteristic compounds in each monofloral variety. Thus, this is a good starting point for the development of new systems focused on the honey sector.     

Botanical discrimination and classification of honey samples applying gas chromatography/mass spectrometry fingerprinting of headspace volatile compounds

A validated method for the discrimination and classification of honey samples performing GC/MS fingerprinting of headspace volatile compounds was developed. Combined mass spectra of honey samples originated from different plants and geographical regions of Greece were subjected to orthogonal partial least squares-discriminant analysis™ (OPLS™-DA), soft independent modelling of class analogy (SIMCA), and OPLS™-hierarchical cluster analysis (OPLS™-HCA). Analyses revealed an excellent separation between honey samples according to their botanical origin with the percentage of misclassification to be as low as 1.3% applying OPLS™-HCA. Fragments (m/z) responsible for the observed separation were assigned to phenolic, terpenoid, and aliphatic compounds present in the headspace of unifloral honeys. On the other hand, a variable classification for citrus and thyme honeys according to their geographical origin could be achieved. Results suggested that the developed methodology is robust and reliable for the botanical classification of honey samples, and the study of differences in their chemical composition.     

Influence of simulated industrial thermal treatments on the volatile fractions of different varieties of honey

The aim of this study was to determine if the volatile fraction of honey is affected by the application of standard industrial thermal treatment processes. Four types of Spanish honey were studied: three of floral origin (citrus, rosemary and polyfloral) and the fourth from honeydew. Each sample of honey was divided into three parts: one was left untreated, one was liquefied (at 45 °C for 48 h) and the other was both liquefied and pasteurized (at 80 °C for 4 min). All the samples analyzed were characterized to determine their melissopalynological, physicochemical (pH, moisture, total acidity, conductivity, hydroxymethylfurfural, and diastase activity), and volatile profiles. Type of honey had a greater impact on volatile fraction variations than did heat treatment. The overall volatile profile of each kind of honey permitted the classification of the honeys by botanical origin, revealing that there were practically no differences between the raw, liquefied, and pasteurized samples of each honey. These findings suggest that industrial processes conducted under controlled conditions should not significantly alter the intrinsic aroma of honey.     

Effect of high-pressure processing on volatile composition and odour of cherry tomato purée

The impact of high-pressure processing on the odour of cherry tomato purée was evaluated by sensory evaluation and SPME–GC/MS analysis. Two temperatures (20 and 60 °C) and two pressures (atmospheric and 800 MPa) were used in processing. Higher pressure at ambient temperature decreased the levels of certain volatile aldehydes, ketones and alcohols present in tomato, whereas, the levels of hexanal, heptanal and octanal increased. The higher temperature combined with either ambient or high-pressure, decreased the levels of many volatile compounds and caused a reduction in the intensity of fresh tomato odour. Processing at 800 MPa and 60 °C resulted in a marked increase in the intensity of cooked tomato and tea-like odour. On the basis of sensory assessment and volatile analysis, high pressure treatment at 800 MPa does not seem to be suitable for preserving fresh tomato odour.     

Changes in the composition of volatile compounds and in microbiological and physicochemical parameters during pastırma processing

Changes in the composition of volatile compounds and in microbiological and physicochemical parameters of past?rma (Turkish dry-cured meat product) were studied during traditional processing. The pH value increased during the last stages of processing. While a_w values decreased throughout processing, TBARS and NPN levels increased regularly depending on the processing time. The microbiological analyses showed that Gram positive-catalase positive cocci were predominant microorganisms in past?rma. A total of forty eight volatile compounds were tentatively identified during past?rma processing, including esters, aliphatic hydrocarbons, sulphur-containing compounds, alcohols, aldehydes, ketones, aromatic hydrocarbons, terpenes and furans. Aldehydes reached their maximum level at the end of second drying. Among aldehydes, hexanal was the major component. In the final product, aromatic hydrocarbons had become the dominant chemical compounds.     

Survey of 1,2-dicarbonyl compounds in commercial honey of different floral origin

In this study we conducted a survey of the concentrations of the major 1,2-dicarbonyl compounds in 40 commercial honey samples from 12 different floral origins. 3-Deoxyglucosone (3-DG), glyoxal (GO), and methylglyoxal (MGO) were measured, using their corresponding quinoxaline derivatives, by high-performance liquid chromatography (HPLC). The analytical performance of the HPLC method for the analysis of 1,2-dicarbonyl compounds was evaluated in terms of linearity, limits of detection (LODs), limits of quantification (LOQs), and precision. Linearity over 2 orders of magnitude, LODs (0.01-0.04 mg/kg), and LOQs (0.03-0.12 mg/kg) were calculated. Instrumental precision, as measured by the repeatability relative standard deviation% (RSDr%), was found to be between 0.22% and 0.55%. Furthermore, the concentrations of factors GO and MGO with respect to 3-DG were also calculated for rapid quantification in honey. In honey samples, the concentrations of 3-DG ranged from 75.9 to 808.6 mg/kg and were significantly higher (up to 100-fold) than those of 5-hydroxymethylfurfural (HMF). Values for GO and MGO were 0.1-10.9 and 0.2-2.9 mg/kg, respectively. The chemical characteristics that most influenced the levels of 1,2-dicarbonyl compounds in honey were found to be pH and total phenols. This was supported by multivariate analysis used to classify different honey types with respect to their chemical characteristics. In addition, both dicarbonyls and phenols are believed to contribute to the development of the final color of honey.     

Characterisation of natural honey proteins: implications for the floral and geographical origin of honey

Characterisation of honey proteins has been considered advantageous for differentiating floral and geographical origin of honey. We analysed protein profiles of multi‐ and mono‐floral honey samples from different regions and harvest dates. The molecular masses of chromatographic peaks were in the range of 10–>200 kDa. Owing to comparable molecular masses, interesting correlation between profiles of honey proteins reported earlier and observed in this study could be established. Chromatograms of honey proteins revealed three novel peaks of molecular masses ～220, 129 and 26 kDa. Statistical analysis of peak areas showed that the 84‐kDa peak was different among all honey samples and the 220‐kDa peak was important for differentiation between multi‐ and mono‐floral honey samples. Chromatograms of several‐year‐old honey samples were different from fresh samples because of depletion of high molecular mass peaks that indicated in situ proteolysis. The results supported the notion of applying gel filtration as cost‐effective and robust technique for honey protein characterisation.     

Ultrasound-assisted extraction gas chromatography–mass spectrometry analysis of volatile compounds in unifloral thyme honey from Greece

The volatile fraction of unifloral Greek thyme honey was investigated by means of ultrasound-assisted extraction followed by GC–MS analysis. Phenolic compounds were the most abundant, followed by short chain fatty acids. In total, 14 compounds are proposed as potent botanical markers for thyme honey, 12 of which are phenolics. Among them, 3-hydroxy-4-phenyl-2-butanone and 3-hydroxy-1-phenyl-2-butanone were the most important, as their concentration averages more than 35 mg/kg of honey. Significant average proportions were found for 1-phenyl-2,3-butanedione, 3-hydroxy-4-phenyl-3-buten-2-one, 3,4,5-trimethoxybenzaldehyde and 3,4,5-trimethoxybenzoic acid. Minor phenolics with statistical significance (p < 0.0001) are phenylacetonitrile, vanillin, 4-hydroxyphenylethanol, 4-hydroxyphenylacetonitrile, and 2-hydroxyacetophenone. Phenylacetaldehyde, a common honey constituent is present at higher concentrations in thyme honey (p < 0.0001). Important non-phenolic components are 2-methylpropionic acid which was found at higher proportions in thyme honey (p = 0.002) and 4-(4-hydroxy-2,2,6-trimethyl-7-oxabicyclo[4.1.0]hept-1-yl)-3-buten-2-one, a norisoprenoid found solely in this type of honey.     

Determination of fermentative volatile compounds in aged red wines by near infrared spectroscopy

The purpose of this work was to study the possibility of determination of fermentative volatile compounds in aged red wines using NIR spectroscopy. To achieve this, 240 wines belonging to different geographic zones and elaborated with one or two varieties were analyzed. The volatile compounds were quantified by SBSE-GC–MS. Spectra obtained by NIR were co-related with these values using partial least square (PLS) regression. Calibration and validation statistics showed the quality of the model, after all when is done separately for each of the four geographic zones, and in the case of wines elaborated with two varieties. Consequently, near infrared spectroscopy can be used as an easy and rapid tool to determine fermentative volatile compounds in aged red wines.     

Effect of the inclusion of chestnut in the finishing diet on volatile compounds during the manufacture of dry-cured “Lacón” from Celta pig breed

The effect of the finishing diet on the volatile compounds throughout the manufacture of dry-cured “lacón” (a Spanish traditional meat product), from the Celta pig breed was studied. Thirty-six pigs were separated into three groups according to the type of feeding during the finish-fattening period of three months (concentrate, mixed diet and chestnut). From the pigs of each diet, four batches of dry-cured “lacón” were manufactured. From each batch, samples of fresh meat, meat after salting, after post-salting, and after 14, 28, 56 and 84 days of drying–ripening were taken. Volatiles were extracted by a purge-and-trap method and analyzed by gas chromatographic/mass spectrometry (GC/MS). Seventy-six volatile compounds were identified and quantified from dry-cured “lacón” samples in pigs finished with chestnut, eighty-two for concentrate fed pigs and eighty in pigs fed with the mixed diet. The number of identified volatile compounds increased during the manufacturing process; at 84 days of drying–ripening, in the dry-cured “lacón” samples from pigs finished with concentrate, mixed diet and chestnut, 54, 58 and 62 volatile compounds were detected, respectively. The most abundant group of flavour compounds at the end of the manufacturing process was hydrocarbons in the three feeding systems, followed by aldehydes, ketones and alcohols. Discriminant analysis selected six variables (dodecane, butadienol, pentenol, 2-pentenal, decen-3-ona and pyridine-2-methyl) and calculated two discriminating functions which allowed verification of chestnut in the finishing diet.     

Phenolic compounds and abscisic acid as potential markers for the floral origin of two Polish unifloral honeys

The phenolic profiles of Polish honey samples from heather (Calluna vulgaris L.) and buckwheat (Fagopyrum esculentum L.) were determined. The phenolic components were isolated from honey samples using Amberlite-XAD-2 as a solid-phase extraction sorbent. For the determination of the composition of the honey extracts HPLC with photodiode array detector was applied. Identification and quantification of phenolics was performed by comparison of their retention times and UV spectra with those of standard solutions of pure reference substances and by using those references as external standards. From among 20 commercially available standards over 15 of them were identified as present in all analysed samples. Taking into account the samples of the same unifloral honeys, similar qualitative but slightly quantitatively different phenolic characteristic profiles were observed. These profiles might be considered as “fingerprints” of heather and buckwheat honeys.     

Vacuum-packed ripened sausages: evolution of volatile compounds during storage

BACKGROUND: Various studies have shown the ability of volatile compounds to influence the quality of charcuterie products because of their effect on sensorial properties. To the best of our knowledge, there are no data in the scientific literature concerning the evolution of volatile compounds of vacuum‐packed ripened sausages over time. The aim of this work was to evaluate the evolution of volatile compounds in vacuum‐packed ripened sausages over time, considering that this kind of packaging is the most commonly used to prolong the shelf‐life of these products. RESULTS: Sixty‐nine volatile compounds were identified. Those derived from spices represented the prevailing compounds at the beginning of storage and significantly decreased (P < 0.001) during 5 months of storage, as a result of the well‐known antioxidant activity. Conversely, compounds derived from the autoxidation of lipids, which are among those chiefly responsible of sensorial properties of meat products, significantly increased (P < 0.001). CONCLUSION: The research demonstrated that vacuum packaging influenced the evolution of volatile compounds during storage of ripened sausages. In particular, the increase of volatile compounds derived from autoxidation of the lipid fraction indicated that oxidative processes involved the fatty fraction of ripened sausages also in the scarcity of oxygen. Copyright © 2011 Society of Chemical Industry