Proton transfer reaction mass spectrometry, a tool for on-line monitoring of acrylamide formation in the headspace of maillard reaction systems and processed food

The formation of acrylamide was measured in real time during thermal treatment (120-170 degrees C) of potato as well as in Maillard model systems composed of asparagine and reducing sugars, such as fructose and glucose. This was achieved by on-line monitoring of acrylamide released into the headspace of the samples using proton transfer reaction mass spectrometry (PTR-MS). Unambiguous identification of acrylamide by PTR-MS was accomplished by gas chromatography coupled simultaneously to electron-impact MS and PTR-MS. The PTR-MS ion signal at m/z 72 was shown to be exclusively due to protonated acrylamide obtained without fragmentation. In model Maillard systems, the formation of acrylamide from asparagine was favored with increasing temperature and preferably in the presence of fructose. Maximum signal intensities in the headspace were obtained after approximately 2 min at 170 degrees C, whereas 6-7 min was required at 150 degrees C. Similarly, the level of acrylamide released into the headspace during thermal treatment of potato was positively correlated to temperature.     

Characterisation of the aroma of green Mexican coffee and identification of mouldy/earthy defect

The aromas of a reference green Mexican coffee (Arabica) and of a coffee from the same origin, but having a pronounced earthy/mouldy off-taint, were characterised. From comparison of the two aroma profiles, the compounds causing the defect were detected by gas chromatography olfactometry, isolated and concentrated by preparative bi-dimensional gas chromatography, and characterised by gas chromatography-mass spectrometry. Six compounds participated in the off-flavour. Geosmin, 2-methylisoborneol, 2,4,6-trichloroanisole were found to be the main culprits, while three methoxy pyrazines (2-methoxy-3-isopropyl/-3-sec-butyl/-3-isobutyl pyrazine) contributed to a lesser extent to the earthy/green undertone. The occurrence of the off-flavour could tentatively be linked to post-harvest drying.     

From the green bean to the cup of coffee: investigating coffee roasting by on-line monitoring of volatiles

Volatile organic compounds (VOCs), emitted from green coffee beans, during coffee roasting and from a cup of coffee, were all analysed by proton-transfer-reaction mass spectrometry. Firstly, the headspace (HS) of green beans was investigated. Alcohols dominate the HS, but aldehydes, hydrocarbons and organic acids were also abundant. Secondly, we roasted coffee under two different conditions and monitored on-line the VOCs emitted during the process. In a first roasting series, a batch of beans was roasted. After an initial drying phase, dominated by evaporation of water and methanol, the HS concentrations of VOCs such as acetic acid, acetaldehyde, pyridine and methylbutanal rapidly increased and went through a maximum at medium roast level. In a second series, just six beans were roasted. We observed sporadic bursts of some volatiles (furans, butanal, 2,3-pentanedione), coinciding with popping sounds. Other VOCs showed smooth time-intensity profiles (pyridine, pyrazine). These experiments gave a real-time insight into the complex processes taking place during roasting. Finally, the HS of coffee extracts, prepared from beans roasted to different roast levels, were analysed. Most VOCs showed a maximum concentration at medium roast level (e.g. pentanedione, furfural, 5-methyl furfural), while others showed a gradual increase (e.g. pyrrol) or decrease (e.g. methanol).     

Comparison of nine common coffee extraction methods: instrumental and sensory analysis

The preparation of a cup of coffee may vary between countries, cultures and individuals. Here, an analysis of nine different extraction methods is presented regarding analytical and sensory aspects for four espressi and five lunghi. This comprised espresso and lungo from a semi-automatic coffee machine, espresso and lungo from a fully automatic coffee machine, espresso from a single-serve capsule system, mocha made with a percolator, lungo prepared with French Press extraction, filter coffee and lungo extracted with a Bayreuth coffee machine. Analytical measurements included headspace analysis with HS SPME GC/MS, acidity (pH), titratable acidity, content of fatty acids, total solids, refractive indices (expressed in °Brix), caffeine and chlorogenic acids content with HPLC. Sensory analysis included visual, aroma, flavor and textural attributes as well as aftersensation. The technical differences in the extraction methods led to a higher concentration of the respective quantities in the espressi than in the lunghi. Regarding the contents per cup of coffee, the lunghi generally had a higher content than the espressi. The extraction efficiency of the respective compounds was mainly driven by their solubility in water. A higher amount of water, as in the extraction of a lungo, generally led to higher extraction efficiency. Comparing analytical data with sensory profiles, the following positive correlations were found total solids ? texture/body, headspace intensity ? aroma intensity, concentrations of caffeine/chlorogenic acids ? bitterness and astringency.     

When machine tastes coffee: instrumental approach to predict the sensory profile of espresso coffee

A robust and reproducible model was developed to predict the sensory profile of espresso coffee from instrumental headspace data. The model is derived from 11 different espresso coffees and validated using 8 additional espressos. The input of the model consists of (i) sensory profiles from a trained panel and (ii) on-line proton-transfer reaction mass spectrometry (PTR-MS) data. The experimental PTR-MS conditions were designed to simulate those for the sensory evaluation. Sixteen characteristic ion traces in the headspace were quantified by PTR-MS, requiring only 2 min of headspace measurement per espresso. The correlation is based on a knowledge-based standardization and normalization of both datasets that selectively extracts differences in the quality of samples, while reducing the impact of variations on the overall intensity of coffees. This work represents a significant progress in terms of correlation of sensory with instrumental results exemplified on coffee.     

Individualization of Flavor Preferences: Toward a Consumer‐centric and Individualized Aroma Science

Personal dietary choices are largely based on flavor preferences. Thus understanding individual flavor perception and preference is vital to understanding the basis of human diet selection. We have developed novel tools to measure in real time and at an individual level volatile aroma compounds delivered breath‐by‐breath to the nose while eating and drinking. The same food may deliver different aromas to different people, due the specificities of their in‐mouth environment (inter‐individual differences). Moreover, a person may eat a given food in a different manner, leading to variations in the aroma profile reaching the nose (intra‐individual differences). Understanding the basis of these differences opens the door to an individualized aroma science and the road to delivering nutritional value and health through products consumers prefer. The challenge to the food industry is to align what the consumer wants with what the consumer needs, delivering nutritional value and health through products they prefer.     

Drug-related hospitalization at a tertiary teaching center in Lebanon: incidence, associations, and relation to self-medicating behavior

OBJECTIVE: In Lebanon there is very limited restriction on drug use. Accordingly, self-medication is highly prevalent. This study examined the influence of these factors on the development of drug-related illnesses that lead to hospitalization. METHODS: Patients admitted to the medical and pediatric wards of a tertiary teaching center in Beirut, Lebanon, over a period of 6 months were interviewed and their charts were reviewed. Admissions attributable to adverse drug reactions or therapeutic failures were identified and characterized with respect to demographic factors, medical history, drug intake, and self-medicating behavior. The influence of these variables on the development of drug-related illnesses was examined by logistic regression. RESULTS: Of 1745 adults and 457 children, there were 177 (10.2%) and 36 (7.9%) drug-related illnesses, respectively. Adverse drug reactions accounted for 7.0% and 5.7% and therapeutic failures for 3.2% and 2.2% of adult and pediatric admissions, respectively. Self-medication was commonly practiced (52.6% of adults and 41.6% of children). Logistic regression analysis revealed that female sex increased the risk of adverse drug reaction in adults, whereas self-medication decreased the risk. In children, the risk of adverse drug reaction was increased in lower socioeconomic groups, whereas the risk of therapeutic failure was increased by a positive history of atopy or drug reaction. CONCLUSIONS: These results provide the first detailed analysis of the problem of drug-related illnesses in a developing country and identify a number of related or risk factors. Despite the lack of regulation of drug dispensing and the unchecked access to drugs in Lebanon, the incidence of drug-related illnesses is not different from that in Western nations. This finding may have relevance to policies of drug regulation in other countries.     

Laser mass spectrometry as on-line sensor for industrial process analysis: process control of coffee roasting

The objective of the project is to develop on-line, real-time, and noninvasive process control tools of coffee roasting that help deliver a consistent and high-quality coffee aroma. The coffee roasting process was analyzed by direct injection of the roaster gas into a time-of-flight mass spectrometer and ionized either by resonance enhanced multiphoton ionization (REMPI) at 266 and 248 nm or vacuum ultraviolet single-photon ionization (VUV-SPI) at 118 nm. The VUV ionization scheme allows detecting mainly the most volatile and abundant compounds of molecular mass below 100 m/z, while REMPI ionizes mainly aromatic compounds of molecular mass larger than 100 m/z. Combining the compounds ionized by resonant and single-photon ionization, approximately 30 volatile organic compounds are monitored in real time. Time-intensity profiles of 10 important volatile coffee compounds were discussed in connection with their formation chemistry during roasting. Applying multivariate statistics (principle component analysis) on time-intensity traces of nine volatile coffee compounds, the roasting degree could be traced as a consistent path in the score plot of the two most significant principle components (including 68% of the total variance), for a range of roasting temperatures (200-250 degrees C).     

Unambiguous identification of volatile organic compounds by proton-transfer reaction mass spectrometry coupled with GC/MS

Interest in on-line measurements of volatile organic compounds (VOCs) is increasing, as sensitive, compact, and affordable direct inlet mass spectrometers are becoming available. Proton-transfer reaction mass spectrometry (PTR-MS) distinguishes itself by its high sensitivity (low ppt range), high time resolution (200 ms), little ionization-induced fragmentation, and ionization efficiency independent of the compound to be analyzed. Yet, PTR-MS has a shortcoming. It is a one-dimensional technique that characterizes compounds only via their mass, which is not sufficient for positive identification. Here, we introduce a technical and analytical extension of PTR-MS, which removes this shortcoming, while preserving its salient and unique features. Combining separation of VOCs by gas chromatography (GC) with simultaneous and parallel detection of the GC effluent by PTR-MS and electron impact MS, an unambiguous interpretation of complex PTR-MS spectra becomes feasible. This novel development is discussed on the basis of characteristic performance parameters, such as resolution, linear range, and detection limit. The recently developed drift tube with a reduced reaction volume is crucial to exploit the full potential of the setup. We illustrate the performance of the novel setup by analyzing a complex food system.