Static and dynamic headspace analysis of instant coffee blends by proton-transfer-reaction mass spectrometry.

Instant coffee is a widespread product, generally related to a high consumer acceptability, also because of its ease of preparation. The present work addresses the characterization of the headspace of freshly brewed instant coffees resulting from different blends, during and immediately after preparation. The sample set consisted of 10 coffees, obtained by mixing three different blends in different proportions. The employment of Proton Transfer Reaction-Mass Spectrometry (PTR-MS) allowed for direct and real-time sampling from the headspace, under conditions that mimic those that are encountered above the cup during and right after brewing. Different coffee brews were separated on the basis of the respective volatile profiles, and data showed good consistency with the respective blend compositions. When the headspace evolution was monitored during preparation, similar results were obtained in terms of blend separation; moreover, different blends displayed different and reproducible 'signatures' in terms of time evolution. A straightforward method for the prediction of headspace composition is proposed, allowing to predict the volatile profiles of two-component and three-component blends on the basis of the respective parent components. Overall, the results constitute a successful example of the applicability of PTR-MS as a tool for product development in food science. Copyright © 2015 John Wiley & Sons, Ltd.

Volatile compound profile of sous-vide cooked lamb loins at different temperature-time combinations.

Lamb loins were subjected to sous-vide cooking at different combinations of temperature (60 and 80°C) and time (6 and 24h) to assess the effect on the volatile compound profile. Major chemical families in cooked samples were aliphatic hydrocarbons and aldehydes. The volatile compound profile in sous-vide cooked lamb loin was affected by the cooking temperature and time. Volatile compounds arising from lipid oxidation presented a high abundance in samples cooked at low or moderate cooking conditions (60°C for 6 and 24h, 80°C for 6h), while a more intense time and temperature combination (80°C for 24h) resulted on a higher concentration of volatile compounds arising from Strecker degradations of amino acids, as 2-methylpropanal and 3-methylbutanal. Therefore, sous-vide cooking at moderately high temperatures for long times would result in the formation of a stronger meaty flavor and roast notes in lamb meat.

Volatile compounds profile of sous-vide cooked pork cheeks as affected by cooking conditions (vacuum packaging, temperature and time).

The volatile organic compound (VOC) profile of pork cheeks as affected by the cooking conditions was investigated. Pork cheeks were cooked under different combinations of temperature (60 °C or 80 °C), time (5 or 12 h) and vacuum (vacuum or air-packaged). As a general rule, the VOCs originating from lipid degradation were positively affected by the cooking temperature and negatively by the cooking time, reaching the highest amounts in pork cheeks cooked at 80 °C during 5 h and the lowest in samples cooked at 80 °C during 12 h. On the contrary, VOCs originated from amino acids and Maillard reactions were positively affected by both factors. The proportion between lipid degradation and amino acids reactions was estimated by the hexanal/3-methylbutanal ratio, which reached its highest values in samples cooked at 60 °C during 5 h in the presence of air and the lowest values in samples cooked at 80 °C during 12 h, regardless of the vacuum status.

PTR-MS in Italy: a multipurpose sensor with applications in environmental, agri-food and health science.

Proton Transfer Reaction Mass Spectrometry (PTR-MS) has evolved in the last decade as a fast and high sensitivity sensor for the real-time monitoring of volatile compounds. Its applications range from environmental sciences to medical sciences, from food technology to bioprocess monitoring. Italian scientists and institutions participated from the very beginning in fundamental and applied research aiming at exploiting the potentialities of this technique and providing relevant methodological advances and new fundamental indications. In this review we describe this activity on the basis of the available literature. The Italian scientific community has been active mostly in food science and technology, plant physiology and environmental studies and also pioneered the applications of the recently released PTR-ToF-MS (Proton Transfer Reaction-Time of Flight-Mass Spectrometry) in food science and in plant physiology. In the very last years new results related to bioprocess monitoring and health science have been published as well. PTR-MS data analysis, particularly in the case of the ToF based version, and the application of advanced chemometrics and data mining are also aspects characterising the activity of the Italian community.

Study of the volatile compounds and odor-active compounds of dry-cured Iberian ham extracted by SPME.

The volatile compounds and the most odor-active compounds of dry-cured Iberian ham were investigated by extracting them using a solid phase microextraction technique with a 2 cm Carboxen/PDMS/DVB fiber. The detection frequency method was applied to estimate the potential contribution of each compound to the odor of hams. Twenty-one volatile compounds were tentatively identified for the first time in dry-cured ham by gas chromatography-mass spectrometry, and eight in dry-cured Iberian ham. Gas chromatography-olfactometry allowed the identification for the first time of six compounds not previously reported as odorants of Iberian ham, and also two odorants were newly identified in dry-cured ham. According to the detection frequency method, the most odor active compounds found were 3-methylbutanoic acid (dirty sock-like smelling), hexanal (cut grass-like odor), 3-methylbutanal (sweaty and bitter almond-like odor), 2-methyl-3-furanthiol (toasted nuts-like odor) and 1-octen-3-one (mushroom-like odor).

Rapid characterization of dry cured ham produced following different PDOs by proton transfer reaction time of flight mass spectrometry (PTR-ToF-MS).

In the present study, the recently developed proton transfer reaction time of flight mass spectrometry (PTR-ToF-MS) technique was used for the rapid characterization of dry cured hams produced according to 4 of the most important Protected Designations of Origin (PDOs): an Iberian one (Dehesa de Extremadura) and three Italian ones (Prosciutto di San Daniele, Prosciutto di Parma and Prosciutto Toscano). In total, the headspace composition and respective concentration for nine Spanish and 37 Italian dry cured ham samples were analyzed by direct injection without any pre-treatment or pre-concentration. Firstly, we show that the rapid PTR-ToF-MS fingerprinting in conjunction with chemometrics (Principal Components Analysis) indicates a good separation of the dry cured ham samples according to their production process and that it is possible to set up, using data mining methods, classification models with a high success rate in cross validation. Secondly, we exploited the higher mass resolution of the new PTR-ToF-MS, as compared with standard quadrupole based versions, for the identification of the exact sum formula of the mass spectrometric peaks providing analytical information on the observed differences. The work indicates that PTR-ToF-MS can be used as a rapid method for the identification of differences among dry cured hams produced following the indications of different PDOs and that it provides information on some of the major volatile compounds and their link with the implemented manufacturing practices such as rearing system, salting and curing process, manufacturing practices that seem to strongly affect the final volatile organic profile and thus the perceived quality of dry cured ham.