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Odor Detection Threshold
The odor detection threshold is the lowest concentration of a certain odor compound that is perceivable by the human sense of smell. The threshold of a chemical compound is determined in part by its shape, polarity, partial charges, and molecular mass. The olfactory mechanisms responsible for a compound's different detection threshold is not well understood. As such, odor thresholds cannot be accurately predicted. Rather, they must be measured through extensive tests using human subjects in laboratory settings. Optical isomers can have different detection thresholds because their conformations may cause them to be less perceivable for the human nose. It is only in recent years that such compounds were separated on gas chromatographs. For raw water treatment and waste water management, the term commonly used is Threshold Odor Number (TON). For instance, the water to be supplied for domestic use in Illinois is 3 TON. Values * The threshold value is the concentration at whi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Odor
An odor (American English) or odour ( Commonwealth English; see spelling differences) is a smell or a scent caused by one or more volatilized chemical compounds generally found in low concentrations that humans and many animals can perceive via their olfactory system. While ''smell'' can refer to pleasant and unpleasant odors, the terms ''scent'', ''aroma'', and ''fragrance'' are usually reserved for pleasant-smelling odors and are frequently used in the food and cosmetic industry to describe floral scents or to refer to perfumes. Odor physiology Sense of smell The perception of odors, or sense of smell, is mediated by the olfactory nerve. The olfactory receptor (OR) cells are neurons present in the olfactory epithelium, which is a small patch of tissue at the back of the nasal cavity. There are millions of olfactory receptor neurons that act as sensory signaling cells. Each neuron has cilia in direct contact with the air. Odorous molecules bind to receptor pro ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Human Nose
The human nose is the first organ of the respiratory system. It is also the principal organ in the olfactory system. The shape of the nose is determined by the nasal bones and the nasal cartilages, including the nasal septum, which separates the nostrils and divides the nasal cavity into two. The nose has an important function in breathing. The nasal mucosa lining the nasal cavity and the paranasal sinuses carries out the necessary conditioning of inhaled air by warming and moistening it. Nasal conchae, shell-like bones in the walls of the cavities, play a major part in this process. Filtering of the air by nasal hair in the nostrils prevents large particles from entering the lungs. Sneezing is a reflex to expel unwanted particles from the nose that irritate the mucosal lining. Sneezing can Transmission (medicine), transmit infections, because aerosols are created in which the Respiratory droplets, droplets can harbour pathogens. Another major function of the nose is olfactio ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Parts Per Billion
In science and engineering, the parts-per notation is a set of pseudo-units to describe the small values of miscellaneous dimensionless quantities, e.g. mole fraction or mass fraction. Since these fractions are quantity-per-quantity measures, they are pure numbers with no associated units of measurement. Commonly used are * parts-per-million - ppm, * parts-per-billion - ppb, * parts-per-trillion - ppt, * parts-per-quadrillion - ppq, This notation is not part of the International System of Units - SI system and its meaning is ambiguous. Applications Parts-per notation is often used describing dilute solutions in chemistry, for instance, the relative abundance of dissolved minerals or pollutants in water. The quantity "1 ppm" can be used for a mass fraction if a water-borne pollutant is present at one-millionth of a gram per gram of sample solution. When working with aqueous solutions, it is common to assume that the density of water is 1.00 g/mL. Therefor ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Vinylguaiacol
2-Methoxy-4-vinylphenol is an aromatic substance used as a flavoring agent. It is one of the compounds responsible for the natural aroma of buckwheat. Some insects such as ''Rhynchophorus ferrugineus'' (Red palm weevil) use this substance for chemical signaling (pheromones). The aroma of pure substance was described as: apple, spicy, peanut, wine-like or clove and curry. Ferulic acid is converted to 2-methoxy-4-vinylphenol by certain strains of yeast, notably strains used in brewing of wheat beers, such as phenolic (POF+) strains of ''Saccharomyces cerevisiae'' (brewer's yeast) which gives beers such as Weissbier and Wit their distinctive spicy "clove" flavor. Various other microbes, including '' Torulaspora delbrueckii'' and ''Pseudomonas fluorescens'' are also able to convert ferulic acid Ferulic acid is a hydroxycinnamic acid derivative and a phenolic compound. It is an organic compound with the formula (CH3O)HOC6H3CH=CHCO2H. The name is derived from the genus '' Ferula'' ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Trimethylamine
Trimethylamine (TMA) is an organic compound with the formula N(CH3)3. It is a trimethylated derivative of ammonia. TMA is widely used in industry. At higher concentrations it has an ammonia-like odor, and can cause necrosis of mucous membranes on contact. At lower concentrations, it has a "fishy" odor, the odor associated with rotting fish. Physical and chemical properties TMA is a colorless, hygroscopic, and flammable tertiary amine. It is a gas at room temperature but is usually sold as a 40% solution in water. It is also sold in pressurized gas cylinders. TMA protonates to give the trimethylammonium cation. Trimethylamine is a good nucleophile, and this reactivity underpins most of its applications. Trimethylamine is a Lewis base that forms adducts with a variety of Lewis acids. Production Industry and laboratory Trimethylamine is prepared by the reaction of ammonia and methanol employing a catalyst: :3 CH3OH + NH3 → (CH3)3N + 3 H2O This reaction coproduces the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Strawberry Furanone
Furaneol, or strawberry furanone, is an organic compound used in the flavor and perfume industry. It is formally a derivative of furan. It is a white or colorless solid that is soluble in water and organic solvents. Odor and occurrence Although malodorous at high concentrations, it exhibits a sweet strawberry aroma when dilute. It is found in strawberries and a variety of other fruits and it is partly responsible for the smell of fresh pineapple. It is also an important component of the odours of buckwheat, and tomato. Furaneol accumulation during ripening has been observed in strawberries and can reach a high concentration of 37 μg/g. Furaneol acetate The acetate ester of furaneol, also known as caramel acetate and strawberry acetate, is also popular with flavorists to achieve a fatty toffee taste and it is used in traces in perfumery to add a sweet gourmand note. Stereoisomerism Furaneol has two enantiomers, (''R'')-(+)-furaneol and (''S'')-(−)-furaneol. The (''R'')-form ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Geosmin
Geosmin ( ) is an irregular sesquiterpenoid with a distinct earthy or musty odor, which most people can easily smell. The geosmin odor detection threshold in humans is very low, ranging from 0.006 to 0.01 micrograms per liter in water. Geosmin, along with the irregular monoterpene 2-methylisoborneol, together account for the majority of biologically-caused taste and odor outbreaks in drinking water worldwide and in Fish farming, farmed fish. Geosmin is also responsible for the earthy taste of beetroots and a contributor to the strong scent, known as petrichor, that occurs when rain falls after a spell of dry weather or when soil is disturbed. In chemical terms, geosmin is a bicyclic molecule, bicyclic alcohol (chemistry), alcohol with chemical formula, formula , a derivative of decalin. It is produced from the universal sesquiterpene precursor farnesyl pyrophosphate (also known as farnesyl diphosphate), in a two-step -dependent reaction. Its name is derived from the Ancient Greek ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sotolon
Sotolon (also known as sotolone) is a butenolide lactone and an extremely potent aroma compound, with the typical smell of fenugreek or curry at high concentrations and maple syrup, caramel, or burnt sugar at lower concentrations. Sotolon is the major aroma and flavor component of fenugreek seed and lovage, and is one of several aromatic and flavor components of artificial maple syrup. It is also present in molasses, aged rum, aged sake and white wine, flor sherry, roast tobacco, and dried fruiting bodies of the mushroom '' Lactarius helvus''. Sotolon can pass through the body relatively unchanged, and consumption of foods high in sotolon, such as fenugreek, can impart a maple syrup aroma to one's sweat and urine. In some individuals with the genetic disorder maple syrup urine disease, sotolon is spontaneously produced in their bodies and excreted in their urine, leading to the disease's characteristic smell. This molecule is thought to be responsible for the mysterious maple s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Parts Per Trillion
In science and engineering, the parts-per notation is a set of pseudo-units to describe the small values of miscellaneous dimensionless quantities, e.g. mole fraction or mass fraction. Since these fractions are quantity-per-quantity measures, they are pure numbers with no associated units of measurement. Commonly used are * parts-per-million - ppm, * parts-per-billion - ppb, * parts-per-trillion - ppt, * parts-per-quadrillion - ppq, This notation is not part of the International System of Units - SI system and its meaning is ambiguous. Applications Parts-per notation is often used describing dilute solutions in chemistry, for instance, the relative abundance of dissolved minerals or pollutants in water. The quantity "1 ppm" can be used for a mass fraction if a water-borne pollutant is present at one-millionth of a gram per gram of sample solution. When working with aqueous solutions, it is common to assume that the density of water is 1.00 g/mL. Therefore, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Grapefruit Mercaptan
Grapefruit mercaptan is a natural organic compound found in grapefruit. It is a monoterpenoid that contains a thiol (also known as a mercaptan) functional group. Structurally a hydroxy group of terpineol is replaced by the thiol in grapefruit mercaptan, so it also called thioterpineol. Volatile thiols typically have very strong, often unpleasant odors that can be detected by humans in very low concentrations. Grapefruit mercaptan has a very potent, but not unpleasant, odor, and it is the chemical constituent primarily responsible for the aroma of grapefruit. This characteristic aroma is a property of only the ''R'' enantiomer. Pure grapefruit mercaptan, or citrus-derived oils rich in grapefruit mercaptan, are sometimes used in perfumery and the flavor industry to impart citrus aromas and flavors. However, both industries actively seek substitutes for grapefruit mercaptans for use as a grapefruit flavorant, since its decomposition products are often highly disagreeable to the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Olympic Swimming Pool
An Olympic-size swimming pool is a swimming pool which conforms to the regulations for length, breadth, and depth made by World Aquatics (formerly FINA) for swimming at the Summer Olympics and the swimming events at the World Aquatics Championships. Different size regulations apply for other pool-based events, such as diving, synchronized swimming, and water polo. Less onerous breadth and depth regulations exist for lesser swimming competitions, but any "long course" event requires a course length of , as distinct from " short course" which applies to competitions in pools that are in length (or in the United States). If touch pads are used in competition, then the distance is relative to the touch pads at either end of the course, so that the pool itself is generally oversized to allow for the width of the pads. An Olympic-size swimming pool is used as a colloquial unit of volume, to make approximate comparisons to similarly sized objects or volumes. It is not a specific de ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
