Application of a comparative aroma extract dilution analysis on aroma distillates isolated from either raw Italian hazelnuts or a roasted hazelnut material produced thereof revealed 37 odor-active compounds in the raw nuts, whereas 46 aroma compounds were detected in the roasted nut material. 2-Methoxy-3-isopropylpyrazine and 2-methoxy-3,5-dimethylpyrazine as well as 5-methyl-4-heptanone predominated with the highest flavor dilution factors in the raw nuts, whereas 2-acetyl-1-pyrroline, 2-propionyl-1-pyrroline, 2-furfurylthiol, and 2-thenylthiol as well as (Z)-2-octenal, (Z)-2-nonenal, and (Z)-2-decenal showed the highest odor activities in the roasted nuts. These odorants, as well as several others, were previously unknown in hazelnuts. In addition, the intensely seasoning-like smelling 3,5,5'-trimethyl-2(5H)-furanone was identified for the first time as a food aroma compound on the basis of a newly developed synthetic route and NMR measurements.
The concentrations of 19 odorants, recently characterized by GC-olfactometry and aroma extract dilution analysis as the most odor-active compounds in raw hazelnuts, were quantitated by stable isotope dilution assays (SIDA). Calculation of odor activity values (OAV) on the basis of odor thresholds in oil revealed high OAVs, in particular for linalool, 5-methyl-4-heptanone, 2-methoxy-3,5-dimethylpyrazine, and 4-methylphenol. A model mixture in sunflower oil containing the 13 odorants showing OAVs above 1 in their natural concentrations resulted in a good similarity compared to the overall nut-like, fruity aroma of the raw hazelnuts. Quantitation of the 25 most odor-active compounds in roasted hazelnut paste by SIDA showed clear changes in the concentrations of most odorants, and formation of new odor-active compounds induced by the roasting process was observed. The highest OAVs were calculated for 3-methylbutanal (malty), 2,3-pentanedione (buttery), 2-acetyl-1-pyrroline (popcorn), and (Z)-2-nonenal (fatty), followed by dimethyl trisulfide, 2-furfurylthiol, 2,3-butanedione, and 4-hydroxy-2,5-dimethyl-3(2H)-furanone. The aroma of a model mixture containing the 19 odorants with OAVs above 1 in their actual concentrations in the roasted nut material was judged to elicit a very good similarity to the popcorn-like, coffee-like, and sweet-smoky aroma of the roasted hazelnut paste. New SIDAs were developed for the quantitation of 5-methyl-4-heptanone, 5-methyl-(E)-2-hepten-4-one, 2-thenylthiol, and 3,5,5-trimethyl-2(5H)-furanone.
During flights, reduced odor and taste perception is reported. Passengers tend to prefer spicier meals than on the ground. The conditions on board were simulated at the Fraunhofer flight test facility in Holzkirchen, Germany, consisting of a front fuselage of an Airbus A310-200 in a huge metal tube in which all relevant parameters can be adjusted (humidity, temperature, pressure). Flight tests were carried out at low atmospheric pressure corresponding to cabin conditions on board at cruising altitude and were repeated at normal atmospheric pressure corresponding to ground conditions. All other parameters were kept constant. Under these conditions, test persons smelled and tasted food-safe flavorants to evaluate the mean odor and taste thresholds and tasted different flavored food. Even tomato juice and various wines were tasted for odor and taste qualities, intensities and individual preferences. At low pressure conditions, higher taste and odor thresholds of flavorants were generally observed with few exceptions. Salt, sugar, glutamate and most odorant thresholds increased clearly. Organic acids and some bitter tastants showed no change. Transferred to complete meals, more salt, sugar and herbs were necessary on board to serve meals that tasted similar to the way they did on the ground. Sour ingredients had to be reduced. The odor and taste spectrum of the beverages investigated changed in various ways. Light and fresh flavors decreased, whereas intensive flavors persisted
The investigation of the cleaning effectiveness of air cleaners under realistic conditions is challenging. Mathematical models are needed to extract characteristic properties of the air cleaning system from experimental data. An incremental evaluation model based on a source term and a total first-order loss coefficient in each segment was developed to analyze indoor particle measurements. The application of the model is demonstrated using two scenarios, one in a well-mixed testing room and another in a fully equipped aircraft cabin at 750 hPa with a typical aircraft ventilation system. In the first scenario, a normalized version of the model is used to eliminate the source's influence. For the investigation in the aircraft cabin, the model served to extract temporal and spatial resolved source terms and first-order loss coefficients. The incremental evaluation model is applicable to enhance the certification of air cleaners. The application of the model is not only limited to particles; measurements of gaseous compounds like ozone, carbon dioxide, or volatile organic compounds can be evaluated analogously. The model's utility for the data analysis of experiments with complex flow conditions should be studied in further investigations.
The current pandemic of the SARS-CoV-2 virus requires measures to reduce the risk of infection. In addition to the usual hygiene measures, air cleaners are a recommended solution to decrease the viral load in rooms. Suitable technologies range from pure filters to inactivating units, such as cold plasma or UVC irradiation. Such inactivating air cleaners, partly combined with filter technology, are available on the market in various designs, dimensions and technical specifications. Since it is not always clear whether they may produce undesirable by-products, and the suitability for particular applications cannot be assessed on the basis of the principle of operation, the effectivity of six inactivating devices was investigated in a near-real environment. The investigations were based on a standard method published by the VDI. The procedure was extended in such a way that a permanent virus source was simulated, which corresponds to the presence of a person suffering from COVID-19 in a room. The study addresses the difference of the mere presence of viruses to the determination of the virulence. As a result, a deep understanding is provided between the behavior of a virus as a pure aerosolized particle and its real infectivity in order to enable the assessment of suitable air cleaners.
Gypsum is widely used in building products, e. g., as drywall, stucco or constituent in mortar, because it is easy to handle and it is assigned creating a good indoor air quality. Odor analysis of a gypsum product with a sulfurous off-odor by means of gas chromatography-olfactometry compared to two unobtrusive commercial gypsum products revealed -apart from typical odor compounds previously found in building products like aldehydes, ketones and acids -various organic sulfur compounds as odorants at very small concentrations (s 1 lg/m 3 ) not allowing structural identification. Gypsum deposits naturally contain impurities and elemental sulfur, which can react in nature due to tectonic pressure and temperature or during production with organic compounds, e. g., from beater additives, to form organic sulfur compounds. Odor analysis of a gypsum raw material and its semi-processed product from a Chinese deposit with a very intense sulfurous off-odor revealed high concentrations of organic sulfur compounds, which were identical in analytical, chromatographic and sensory properties to the unidentified sulfur compounds of the commercial products and are therefore suitable for structural identification of those unknowns. In this way, a number of sulfides, disulfides, thiols and aromatic sulfur compounds could be identified as contributing to the odor of gypsum products.
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