Smell human response

It is difficult to predict the effect of toxic gases on the human body with any degree of certainty. Obviously, people cannot be tested directly, so data is normally taken from tests with laboratory animals. Assumptions then have to be made as to how similar human response would be to that of the animals. Moreover, two people with very similar physiologies may react to a chemical quite differently. For example, the toxic gas H2S has a strong odor at moderate concentrations. However, when the concentration rises above a certain point, human olfactory nerves are disabled and so the gas cannot be smelled. Thus H2S famously has the property that If you can smell it you re in trouble, if you can t smell it you re in real trouble. Unfortunately, the odor threshold varies significantly from person to person, hence the sense of smell cannot be used as a reliable gauge to do with the presence of toxic gases. 

Human responses to sensory stimulation with liquids introduced into the oral cavity have been compared with orthonasal (smelling via the anterior nares) olfactory judgments in a number of studies (e.g., [22 27]). Interactions between the oral liquids and orthonasal odorants were often... 

For quality control purposes it is the case at present that human smell panels will be used in preference to instrumental analytical techniques which do not yet adequately mimic the human response. There are practical drawbacks to this approach, leading to a lot of research going into electronic noses utilising a number (e.g., 32) of sensors based on organic conducting polymers. These devices enable fingerprints of satisfactory products to be recorded which are used as references for quality checks. 

Whatever the physiology of odor perception may be, the sense of smell is keener than that of taste (22). If flavors are classed into odors and tastes as is common practice in science, it can be calculated that there are probably more than 10 possible sensations of odor and only a few, perhaps five, sensations of taste (13,21,35—37). Just as a hereditary or genetic factor may cause taste variations between individuals toward phenylthiourea, a similar factor may be in operation with odor. The odor of the steroid androsterone, found in many foods and human sweat, may eflcit different responses from different individuals. Some are very sensitive to it and find it unpleasant. To others, who are less sensitive to it, it has a musk or sandalwood-like smell. Approximately 50% of the adults tested cannot detect any odor even at extremely high concentrations. It is befleved that this abiUty is genetically determined (38). 

In 1986, the National Geographic Society, in cooperation with the MoneU Center, conducted a worldwide survey of the sense of smell. Over 10 million survey forms were sent to readers of the Society s journal, of which close to 1.5 million forms were completed and returned. With responses to 40 demographic and 42 odor-related questions, the results constitute the largest set of data on human olfaction (4). 

Later in intra-uterine life, the human infant is susceptible to early chemical prompting, but again the affector route is not known with certainty. Neonatal discrimination in favour of familiar (maternal) amniotic fluid is demonstrable, suggesting that the foetus already has active chemosensory capacities (Schaal, 1998). Smell and taste are operative in the near full-term foetus since it shows detection of about 120 mg/day maternal intake of anethole (as anise condiments) within a few days before parturition this exposure induced subsequent preferential responses by babies to anethole (Schaal et ai, 2000). The human neonate is not likely to have its organ as a fully functioning chemosensor,... 

Steiner, J. E. (1979). Human facial expressions in response to taste and smell stimulation. In H. Reese L. P. Lip-sitt (Eds.), Advances in Child Development and Behavior (pp. 257—293). New York Academic. 

Not surprisingly, much research in sharks, skates and rays has focused on the responses of sharks to human body odors. Human blood attracts sharks, while sweat does not, and urine was even slightly repellent (Tester, 1963). Practitioners use whale meat and mixtures of fish meal and fish oils as shark attrac-tants. In both carnivorous and herbivorous bony fish (Osteichthyes) smell deals with prey odors, social odors, and chemical stimuli in homing, and it is mediated by the first cranial nerve, the olfactory nerve. By contrast, taste serves in detection and selection of food and avoidance of toxic food, and it employs the facial, glossopharyngeal, vagal, and hypoglossal nerves. 

Herz, R. S. and Inzlicht, M. (2002). Sex differences in response to physical and social factors involved in human mate selection the importance of smell for women. Evolution... 

Oxalic acid is poisonous to humans, but its concentrations are generally too low in foods to be of concern, although rhubarb leaves are quite poisonous. Lactic acid is produced from the fermentation of lactose, which is the principal sugar found in milk. The taste and smell of sour milk is due to the production of lactic acid from bacterial fermentation. Lactic acid accumulates in our muscles during exercise and strenuous physical activity. It is responsible for the sore, aching feeling often associated with these activities. Benzoic acid is the simplest aromatic carboxylic acid. 

Human perception of flavor occurs from the combined sensory responses elicited by the proteins, lipids, carbohydrates, and Maillard reaction products in the food. Proteins Chapters 6, 10, 11, 12) and their constituents and sugars Chapter 12) are the primary effects of taste, whereas the lipids Chapters 5, 9) and Maillard products Chapter 4) effect primarily the sense of smell (olfaction). Therefore, when studying a particular food or when designing a new food, it is important to understand the structure-activity relationship of all the variables in the food. To this end, several powerful multivariate statistical techniques have been developed such as factor analysis Chapter 6) and partial least squares regression analysis Chapter 7), to relate a set of independent or "causative" variables to a set of dependent or "effect" variables. Statistical results obtained via these methods are valuable, since they will permit the food... 

Thousands of people in Britain, and Europe died of cholera during the nineteenth century. At that time there was no known cure and no connection was made between the incidence of cholera and the unsanitary conditions. In the cities human excrement was thrown into open sewers flowing down the streets and into rivers. The rivers were also the source of drinking water. London was known as the city of smells. The disease was thought to be carried by the smells . The conditions were only improved when major underground sewers were built in the 1880s. It was also realized that there were very small organisms such as bacteria and viruses. The bacterium responsible for cholera was discovered by Robert Koch in 1883. 

Human beings can detect and distinguish thousands of different compounds by smell, often with considerable sensitivity and specificity. Most odorants are relatively small organic compounds with sufficient volatility that they can be carried as vapors into the nose. For example, a major component responsible for the smell of almonds is the simple aromatic compound benzaldehyde, whereas the sulfhydryl compound 3-methylbutane-l-thiol is a major component of the smell of skunks. 

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