Mass Spectrometry-based Electronic Nose Research Articles

Mass spectrometry-based electronic nose to authenticate 100% Italian durum wheat pasta and characterization of volatile compounds

Headspace solid-phase microextraction (HS-SPME) coupled with mass spectrometry-based electronic nose (MS-eNose), in combination with multivariate statistical analysis was used as untargeted method for the rapid authentication of 100% Italian durum wheat pasta. Among the tested classification models, i.e. PCA-LDA, PLS-DA and SVMc, SVMc provided the highest accuracy results in both calibration (90%) and validation (92%) processes. Potential markers discriminating pasta samples were identified by HS-SPME/GC–MS analysis. Specifically, the content of a pattern of 8 out of 59 volatile organic compounds (VOCs) was significantly different between samples of 100% Italian durum wheat pasta and pasta produced with durum wheat of different origins, most of which were related to different lipidic oxidation in the two classes of pasta. The proposed MS-eNose method is a rapid and reliable tool to be used for authenticating Italian pasta useful to promote its typicity and preserving consumers from fraudulent practices.

Physicochemical, antioxidant, volatile component, and mass spectrometry-based electronic nose analyses differentiated unrefined non-centrifugal cane, palm, and coconut sugars

Unrefined non-centrifugal sugars in Southeast Asia emanate from various plant sources including sugarcane, palm, and coconut. To assess food and flavor characteristic differences of these unrefined sugars, seven cane, three palm, and two coconut sugars were evaluated in term of their physicochemical, antioxidant, and volatile flavor properties. Results indicated that unrefined sugars from cane had significantly higher ICUMSA color value than palm and coconut sugars, yet they possessed comparable total soluble solid levels. Cane sugars also presented superior phenolic and flavonoid contents and antioxidant activities, particularly in Thai and Japanese products. Each sugar had distinct volatile flavor composition, comprising acids, Maillard reaction products (furanone, pyrazine, furan, and pyrrole), aldehydes, alcohols, and sulfurs. All traditionally made unrefined sugars had significantly greater Maillard reaction products and less acetic acid than in industrially manufactured cane sugars. Then, propanoic acid and [R-(R*,R*)]-2,3-butanediol were solely major volatiles in palm sugars from Thailand. Additionally, mass spectrometry-based electronic-nose (e-nose) profiling detection provided specific ion masses from various volatile components as potential chemical markers in monitoring aroma characteristic of unrefined sugars and differentiated these sugars into nine statistical clusters based on their materials and origins, wherein palm sugars from Thailand and Indonesia, as well as cane sugars from Thailand and Japan, had comparable volatile profiles.

Discrimination of geographical origin of oranges (Citrus sinensis L. Osbeck) by mass spectrometry-based electronic nose and characterization of volatile compounds

An untargeted method using headspace solid-phase microextraction coupled to electronic nose based on mass spectrometry (HS-SPME/MS-eNose) in combination with chemometrics was developed for the discrimination of oranges of three geographical origins (Italy, South Africa and Spain). Three multivariate statistical models, i.e. PCA/LDA, SELECT/LDA and PLS-DA, were built and relevant performances were compared. Among the tested models, SELECT/LDA provided the highest prediction abilities in cross-validation and external validation with mean values of 97.8% and 95.7%, respectively. Moreover, HS-SPME/GC-MS analysis was used to identify potential markers to distinguish the geographical origin of oranges. Although 28 out of 65 identified VOCs showed a different content in samples belonging to different classes, a pattern of analytes able to discriminate simultaneously samples of three origins was not found. These results indicate that the proposed MS-eNose method in combination with multivariate statistical analysis provided an effective and rapid tool for authentication of the orange's geographical origin.

전자코를 이용한 가열 중 레토르트 파우치로부터 발생한 휘발성분의 분석

The objective of this study was to analyze the volatile changes occurring in retort pouches during heating using a mass spectrometry-based electronic nose. The data obtained by the electronic nose analysis was used to generate a discriminant function analysis plot. The plot showed that volatile compounds of the heated water in the retort pouch were increased by the interaction between container and water as the heating time increased. Conversely, volatile compounds of the container itself decreased when only the container was measured separately. This result means that volatile compounds from the packaging material migrated into the water. In the case of heated beef bone soup, volatile compounds were increased compared to the unheated beef bone soup after 20 min of heating. According to the results of GC/MS, nonanal and 3,5-di-tert-butyl-4-hydroxytoluene (BHT) were detected in the heated water and nonanal, heptanal, octanal, and BHT were detected in the heated beef bone soup.

Headspace-programmed temperature vaporizer-mass spectrometry and pattern recognition techniques for the analysis of volatiles in saliva samples

A rapid method for the analysis of volatiles in saliva samples is proposed. The method is based on direct coupling of three components: a headspace sampler (HS), a programmable temperature vaporizer (PTV) and a quadrupole mass spectrometer (qMS).Several applications in the biomedical field have been proposed with electronic noses based on different sensors. However, few contributions have been developed using a mass spectrometry-based electronic nose in this field up to date.Samples of 23 patients with some type of cancer and 32 healthy volunteers were analyzed with HS-PTV-MS and the profile signals obtained were subjected to pattern recognition techniques with the aim of studying the possibilities of the methodology to differentiate patients with cancer from healthy controls. An initial inspection of the contained information in the data by means of principal components analysis (PCA) revealed a complex situation were an overlapped distribution of samples in the score plot was visualized instead of two groups of separated samples. Models using K-nearest neighbors (KNN) and Soft Independent Modeling of Class Analogy (SIMCA) showed poor discrimination, specially using SIMCA where a small distance between classes was obtained and no satisfactory results in the classification of the external validation samples were achieved. Good results were obtained when Mahalanobis discriminant analysis (DA) and support vector machines (SVM) were used obtaining 2 (false positives) and 0 samples misclassified in the external validation set, respectively. No false negatives were found using these techniques.

Discrimination of the cultivar, growing region, and geographical origin of rice (Oryza sativa) using a mass spectrometer-based electronic nose.

The objective of this study was to discrimination the cultivar, growing region, and geographical origin of rice (Oryza sativa) using a mass spectrometry-based electronic nose (MSE-nose). The inside-needle dynamic extraction (INDEX) system was used to concentrate the samples for MSEnose, following which the ion fragment data obtained were used to perform discriminant function analysis. Discriminant functions 1 and 2 readily separated all 16 cultivars of rice sampled. It was also confirmed that MSE-nose could distinguish the region in which rice cv. Chucheong and Koshihikari were grown, likely due to variation in environmental factors, such as soil and climate. Finally, it was confirmed that MSE-nose could be used to detect the geographical origin of rice, discrimination Korea rice from Japanese rice. Therefore, this simple and rapid technique is of value for discriminating the cultivar, growing region, and geographical origin of rice.

전자코를 이용한 도정 및 저장에 따른 쌀의 휘발성분 패턴 판별

쌀의 도정도에 따른 휘발성분의 변화를 알아보기 위하여 전자 코 분석을 시행하여 보았다. 그 결과 도정도가 증가할수록 대조구인 공기와 DF1의 거리가 가까워져 적은 휘발성분을 갖는 것으로 나타났다. 이는 도정도를 전자코로 판별할 수 있다고 보여진다. 또한 도정도에 따른 쌀의 저장기간이 늘어날수록 휘발 성분이 증가하는 것을 보여주었다. 이는 쌀을 저장 하였을 경우 지방의 산패가 일어나게 되고 이는 곧 이취로 이어지게 되기 때문에 저장기간이 길어질수록 휘발 성분이 많아지는 것으로 여겨진다. The objective of this study was to analyze the volatile compounds in rice under various milling degrees using a mass spectrometry-based electronic nose and discriminant function analysis (DFA). Less volatile components were more frequently found in rice with a lower milling degree. Milling degree resulted in a shift of DF1 to the left side of the DFA plot. This indicated that the DF1 scores were correlated with the milling degree of rice. Brown rice was found to have more volatile components regardless of the milling degree. Thus, rice prepared at different milling degrees could be effectively discriminated with electronic nose analysis. Moreover, more volatile components were detected with an increase in storage time. A slight change in volatile components was found with an increase in the milling degree. The electronic nose could predict the milling degree and storage time of rice.

전자코와 전자혀를 이용한 시판 증류주의 향미특성 분석

The objective of this study was to analyze the flavor patterns of commercial Korean distilled spirits using a mass spectrometry-based electronic nose and an electronic tongue. Thirteen types of domestic distilled spirits were used for analysis. The flavor patterns of the distilled spirits were clearly identified through discriminant function analysis of the raw materials. The obtained data of the electronic nose analysis showed that the flavor pattern of the distilled spirits aged in oak barrels was not significantly different from that of the general distilled spirits. According to the results of the electronic tongue, the distilled spirits made with rice had a stronger flavor than those made with foxtail millet. Compared to the sensitivity value of each taste sensor, the distilled spirits showed various intensities of sourness and umami. Therefore, an electronic nose and electronic tongue could be successfully used for quality evaluation and new product development of distilled spirits.

Effect of various light emitting diode irradiation on volatile profiles of perilla oil using mass spectrometry-based electronic nose

Volatile component changes in perilla oil caused by Light Emitting Diode (LED) irradiation at different wavelengths, darkness, and fluorescence light were evaluated using an MS-based electronic nose. Volatile component data were analyzed using discrimination function analysis (DFA) for perilla oil stored in amber vials for 12 weeks. The best storage condition was darkness. The largest volatile change occurred under blue LED and fluorescent irradiation. Rapid changes in volatile components were caused by fluorescent irradiation in the initial storage period, and by blue LED irradiation after 4 weeks. Overall volatile component changes were reduced under red and green LED irradiation, and least under darkness. Similarity was observed for influential ion fragments at 52 amu (atomic mass units) in the initial stage of storage, and for 78 amu after 4 weeks of storage.

Discrimination of doenjang samples using a mass spectrometry-based electronic nose and human sensory preference testing

Doenjang samples were discriminated using a mass spectrometry-based electronic nose (MS-E-nose) and discriminant function analysis (DFA). Human sensory preference testing was performed using the same samples. DFA plots indicated classification of doenjang samples into 3 groups. Samples with high discriminate function (DF) 1 and low DF2 scores contained fewer volatile compounds. Grouping results using the MS-E-nose and human sensory preference testing were compared. Fully mashed doenjang samples with more diverse and intense volatile compounds showed low DF1 and high preference scores. DF2 scores for selected samples showed positive correlations to the amount of sample. The MS-E-nose was a useful tool for discrimination of the aroma of doenjang samples and for confirmation of changes in the aroma intensities of doenjang samples.

Sensitivity Enhancement in the Determination of Volatile Biomarkers in Saliva Using a Mass Spectrometry-Based Electronic Nose with a Programmed Temperature Vaporizer

With a view to improving the sensitivity of direct coupling of a headspace sampler (HS) with a mass spectrometer (MS), here we propose the use of a programmed temperature vaporizer (PTV) in solvent-vent injection mode before the sample is introduced into the MS. This preconcentration scheme has been used for some time in many methods based on gas chromatography (GC), but to the best of our knowledge it has not yet been used in an electronic nose based on MS. The increase in the S/N ratio with the proposed instrumental configuration (HS-PTV/MS) lies between 6.9- and 22-fold. The main advantage of using this injector lies in the fact that it does not involve time-consuming steps. To check the possibilities of this methodology, saliva samples from healthy volunteers and patients with different types of illnesses (including some types of cancer) were analyzed. None of the compounds studied was detected in the samples corresponding to the healthy volunteers. One or more biomarkers, at levels ranging from 13 to 500 μg/L, were found in five of the samples from the patients. Additionally, separative analysis by HS-PTV-GC/MS was performed for confirmatory purposes and both methods provided similar results. The main advantage of the proposed methodology is that no prior chromatographic separation and no sample manipulation are required.

Qualitative and quantitative prediction of volatile compounds from initial amino acid profiles in Korean rice wine (makgeolli) model.

In Korean rice wine (makgeolli) model, we tried to develop a prediction model capable of eliciting a quantitative relationship between initial amino acids in makgeolli mash and major aromatic compounds, such as fusel alcohols, their acetate esters, and ethyl esters of fatty acids, in makgeolli brewed. Mass-spectrometry-based electronic nose (MS-EN) was used to qualitatively discriminate between makgeollis made from makgeolli mashes with different amino acid compositions. Following this measurement, headspace solid-phase microextraction coupled to gas chromatography-mass spectrometry (GC-MS) combined with partial least-squares regression (PLSR) method was employed to quantitatively correlate amino acid composition of makgeolli mash with major aromatic compounds evolved during makgeolli fermentation. In qualitative prediction with MS-EN analysis, the makgeollis were well discriminated according to the volatile compounds derived from amino acids of makgeolli mash. Twenty-seven ion fragments with mass-to-charge ratio (m/z) of 55 to 98 amu were responsible for the discrimination. In GC-MS combined with PLSR method, a quantitative approach between the initial amino acids of makgeolli mash and the fusel compounds of makgeolli demonstrated that coefficient of determination (R(2)) of most of the fusel compounds ranged from 0.77 to 0.94 in good correlation, except for 2-phenylethanol (R(2) = 0.21), whereas R(2) for ethyl esters of MCFAs including ethyl caproate, ethyl caprylate, and ethyl caprate was 0.17 to 0.40 in poor correlation. The amino acids have been known to affect the aroma in alcoholic beverages. In this study, we demonstrated that an electronic nose qualitatively differentiated Korean rice wines (makgeollis) by their volatile compounds evolved from amino acids with rapidity and reproducibility and successively, a quantitative correlation with acceptable R2 between amino acids and fusel compounds could be established via HS-SPME GC-MS combined with partial least-squares regression. Our approach for predicting the quantities of volatile compounds in the finished product from initial condition of fermentation will give an insight to food researchers to modify and optimize the qualities of the corresponding products.

Mass spectrometry-based electric nose system for assessing rice quality during storage at different temperatures

A mass spectrometry-based electronic nose (MS e-nose) was used to measure changes in rice quality during storage at different storage conditions. Rice was stored for 4 months at four different temperatures (0 °C, 20 °C, 30 °C, and 40 °C) and tested for fat acidity, sensory characteristics, and flavor pattern analysis using the MS e-nose. When the rice was stored for long durations at higher temperatures, fat acidity increased and sensory quality was low. Flavor volatile profiles of the rice determined by MS e-nose revealed a tendency for the results to separate into three groups (months 1 + 2, 3, and 4). Volatile profile changes in rice during storage depended on the storage time, regardless of storage temperature. It is likely that the fat acidity and sensory evaluation results, which were related, could be distinguished by their volatile-producing metabolic activities. Accordingly, MS e-nose system was successfully used to screen and qualitatively evaluate stored rice.

Volatile profiling of high quality hazelnuts (Corylus avellana L.): Chemical indices of roasting

The study proposes an investigation strategy to identify sensitive, robust and reliable chemical markers of hazelnut roasting. A fully-automated and validated analytical method, based on Headspace Solid Phase Microextraction (HS-SPME) coupled with Gas Chromatography–Mass Spectrometric detection (GC–MS), for effective off-line monitoring of changes in the volatile profile of high-quality hazelnuts was developed. Samples from two different harvests were submitted to roasting, following different time/temperature protocols and different technologies, enabling chemical changes to be correlated with technological processing and sensory quality. Chemical indices, expressed as analyte response ratio, were defined and their trend observed across roasting profiles. Reliability and robustness of chemical indices were also evaluated, in view of their application to on-line monitoring with Mass Spectrometry-based electronic nose technology (MS-nose). Experiments, simulating on-line chemical characterisation of the volatile fraction, were performed through a fully-automated system. The results confirmed: (a) the effectiveness of single process indicators of roasting selected by the separative method (5-methylfurfural, 1(H)-pyrrole, furfuryl alcohol, 1(H)-pyrrole-2-carboxaldehyde, 1-hydroxy-2-propanone, dihydro-2(3H)-furanone, 5-methyl-(E)-2-hepten-4-one, acetic acid, pyridine, furfural, pyrazine, and several alkyl-pyrazines); and, (b) the reliability of proposed chemical indices: 5-methylfurfural/2,5-dimethylpyrazine, 5-methylfurfural/2-methylpyrazine, 2,5-dimethylpyrazine/2,3-dimethylpyrazine; these maintained a consistent trend versus harvest and sampling/analysis technology.

여러 가지 LED를 처리한 전지유, 무지방 우유, LTLT, UHT, HTST 처리 우유의 휘발성분 패턴 분석

The objective of this study was to analyze the pattern recognition of volatile compounds from different types of milk underLED (Light Emitting Dioxide) irradiation for 6 d. Yellow, red, blue, dark, and fluorescent light were produced using LEDequipment. A mass spectrometry-based electronic nose and DFA (discriminant function analysis) were used to determinethe change in volatiles from different types of milk under LED irradiation. As the LED exposure time was increased, DF1of whole milk changed considerably under blue light, while that of skim milk changed significantly under red and yellowlight irradiation. Among the types of milk tested, the most light-induced oxidation sample was LTLT milk under blue light.The volatile compounds that were shown to increase due to LED treatment in the electronic nose analysis, which was basedon MS, were mainly acetaldehyde, propanal, pentanal, hexanal, heptanal, nonanal, 3-methyl butanal, 2-methyl propanal, 2-butanone, 2-pentanone, 2-hexanone, and 2-heptanaone and 2-nonanone. Key words: light emitting dioxide, volatile compound, milk, electronic nose

Classification of Tempranillo wines according to geographic origin: Combination of mass spectrometry based electronic nose and chemometrics

Rapid methods employing instruments such as electronic noses (EN) or gas sensors are used in the food and beverage industries to monitor and assess the composition and quality of products. Similar to other food industries, the wine industry has a clear need for simple, rapid and cost effective techniques for objectively evaluating the quality of grapes, wine and spirits. In this study a mass spectrometry based electronic nose (MS-EN) instrument combined with chemometrics was used to predict the geographical origin of Tempranillo wines produced in Australia and Spain. The MS-EN data generated were analyzed using principal components analysis (PCA), partial least squares discriminant analysis (PLS-DA) and stepwise linear discriminant analysis (SLDA) with full cross validation ( leave-one-out method). The SLDA classified correctly 86% of the samples while PLS-DA 85% of Tempranillo wines according to their geographical origin. The relative benefits of using MS-EN will provide capability for rapid screening of wines. However, this technique does not provide the identification and quantitative determination of individual compounds responsible for the different aroma notes in the wine.

Comparison of Metal Oxide-Based Electronic Nose and Mass Spectrometry-Based Electronic Nose for the Prediction of Red Wine Spoilage

Taints caused by Brettanomyces sp. spoilage are of concern to winemakers and consumers. Typically the taints are described as "barnyard", "sweaty saddle", and "Band-aid" when present in red wine at concentrations of several hundred micrograms per liter or more. The two main components of the taint are 4-ethylphenol (4EP) and 4-ethylguaiacol (4EG), which are metabolites produced by Brettanomyces yeasts. There is a need for a rapid instrumental method to quantify these compounds in wines. In this paper are compared two techniques, the metal oxide sensor-based electronic nose (MOS-Enose) and the mass spectrometry-based electronic nose (MS-Enose). Gas chromatography-mass spectrometry (GC-MS) was used for quantification and prediction purposes. Following ethanol removal, the limits of detection of a MOS-Enose were determined as 44 microg L(-1) for 4EP and 91 microg L(-1) for 4EG, using the SY/gCT sensor. These values are significantly lower than the reported human sensory thresholds. Partial least-squares (PLS) regression of electronic nose signals against known levels of 4EP and 4EG in 46 Australian red wines showed that the MOS-Enose was unable to identify "brett" spoilage reliably because of the response of the gas sensors to intersample variation in volatile compounds other than ethylphenols. Conversely, the MS-Enose was capable of reliably estimating concentrations of 4EP higher than 20 microg L(-1). Correlations (r2) of 0.97 and 0.98 were obtained between estimates of 4EP and 4EG concentrations with the concentrations determined by conventional GC-MS. It is concluded that, following ethanol removal, existing metal oxide sensors are sufficiently sensitive to detect brett taints in wine but lack the selectivity needed to perform this task when the aroma volatile background varies.

Usefulness of chemometrics and mass spectrometry-based electronic nose to classify Australian white wines by their varietal origin

A combination of mass spectrometry-based electronic nose (MS e_nose) and chemometrics was explored to classify two Australian white wines according to their varietal origin namely Riesling and unwooded Chardonnay. The MS e_nose data were analysed using principal components analysis (PCA), discriminant partial least squares (DPLS) and linear discriminant analysis (LDA) applied to principal components scores and validated using full cross validation (leave one out). DPLS gave the highest levels of correct classification for both varieties (>90%). LDA classified correctly 73% of unwooded Chardonnay and 82% of Riesling wines. Even though the conventional analysis provides fundamental information about the volatile compounds present in the wine, the MS e_nose method has a series of advantages over conventional analytical techniques due to simplicity of the sample-preparation and reduced time of analysis and might be considered as a more convenient choice for routine process control in an industrial environment. The work reported here is a feasibility study and requires further development with considerably more commercial samples of different varieties. Further studies are needed in order to improve the calibration specificity, accuracy and robustness, and to extend the discrimination to other wine varieties or blends.

Early detection of fungal growth in bakery products by use of an electronic nose based on mass spectrometry.

This paper presents the design, optimization, and evaluation of a mass spectrometry-based electronic nose (MS e-nose) for early detection of unwanted fungal growth in bakery products. Seven fungal species (Aspergillus flavus, Aspergillus niger, Eurotium amstelodami, Eurotium herbariorum, Eurotium rubrum, Eurotium repens, and Penicillium corylophillum) were isolated from bakery products and used for the study. Two sampling headspace techniques were tested: static headspace (SH) and solid-phase microextraction (SPME). Cross-validated models based on principal component analysis (PCA), coupled to discriminant function analysis (DFA) and fuzzy ARTMAP, were used as data treatment. When attempting to discriminate between inoculated and blank control vials or between genera or species of in vitro growing cultures, sampling based on SPME showed better results than those based on static headspace. The SPME-MS-based e-nose was able to predict fungal growth with 88% success after 24 h of inoculation and 98% success after 48 h when changes were monitored in the headspace of fungal cultures growing on bakery product analogues. Prediction of the right fungal genus reached 78% and 88% after 24 and 96 h, respectively.

An electronic nose and a mass spectrometry-based electronic nose for assessing apple quality during shelf life

Abstract The potential of the electronic nose (E-nose) and the mass spectrometer-based E-nose (MSE-nose) to monitor changes in apple fruit volatiles during shelf life was studied. These techniques were compared with a traditional technique to measure volatiles, gas chromatography combined with mass spectrometry (GC/MS). Apples were stored for 8 months at three different storage conditions and the volatile profile changes were followed subsequently over a period of 15 days. Analysis of the score plot of the principal components analysis for the E-nose measurements showed no storage history effect and only very little shelf life effect. In contrast, the MSE-nose and GC/MS score plots clearly indicated the presence of both shelf life and storage history trend. Moreover, the volatile profile changes during shelf life depended on the storage history. The loading plots of the PCA of the GC/MS data revealed which volatiles are important to differentiate between storage conditions and which ones are important during ripening on the shelf. Partial least square (PLS) models based on the three data sets to relate firmness and days of shelf life with the volatile production of apples were built based on the three data sets. It was found that the models based on the E-nose data had worse prediction performance than those based on the MSE-nose data. Both for firmness (0.95) and days of shelf life (0.98) a high cross-validation correlation was observed between measured and predicted values. The standard error of prediction (S.E.P.) of firmness and shelf life were 2.38×10 6 Hz 2 g 2/3 and 1.02 days, respectively. Models based on the GC/MS data showed comparable results.