Odour Intensity Value

TBA = thiobarbituric acid, PV = peroxide value, HV = hydroperoxide value, OIV = odour intensity value. 

The investigations of dust from piggeries show that both VFA and phenols/indoles are present in a considerable amount. However, compared to the air-borne emissions calculated on the base of the results of LOGTENBERG and STORK (38) less than the tenth part (1/10) of phenols/indoles and about the hundredth part (1/100) of VFA are emitted by the dust, only. Table VII compares the dust-borne and air-borne emissions of VFA and phenols from piggeries. The total amounts are given in addition to the amounts of butyric acid and p-cresol which are both known as intensively smelling compounds. The recognition odour threshold values of these two components are included, as well. Under the assumption of a dust concentration of 10 mg/m3 (7) one cubic meter of air... 

Flavourings consist of a blend of flavouring substances, which can be classified as lipophilic or hydrophilic. Fat or oil serves as carrier of lipophilic, and water as carrier of hydrophilic substances. Tab. 5.4 shows the variation in odour threshold values of selected flavouring substances when placed in water vs. oil. Due to these great variations, reduction in fat levels of foods will affect not only the intensity of the flavour but also its balance, since only little or no carrier system is available for lipophilic flavour components in water. The lipophilic part of the flavour cannot be retained in the food matrix and is released immediately. Fat-reduced or fat-free foods show high flavour impact initially which dissipates quickly, while full fat products gradually build up intensity and dissipate more slowly (schematically depicted in Fig. 5.25). 

Besides the questionable use of the term perceived air quality, which can involve many parameters other than dissatisfaction and acceptability (e.g. odour intensity, stuffiness, perceived dryness, degree of unpleasantness) [3], the main item that is discussed with this method is the assumption that all pollutants have the same relation between exposure and response, i.e. that the calculated olf values from separate sources can be simply added. 

Patte, F. Etcheto, M. and Laffort, P. Selected and standardized values of suprathreshold odour intensities for 110 substances. Chem. Sens. Flav., 1975, 1, 283-307. 

The ability to perceive the odour of a particular substance also depends on its odour threshold (aroma, fiavour) value, which is the concentration of a substance detectable by the sense of smeU. The odour detection threshold value is the lowest concentration of a stimulus (odoriferous substance), which can be detected in comparison with an environment that does not contain this substance. The odour recognition threshold value is the concentration at which a substance can not only be detected, but also recognised. It corresponds to a concentration that allows identification of the odour quality of a substance, which is usually higher than the odour detection threshold. Both values are measures of the odour intensity, but depend considerably on the environment, solubility, partition coefficients between air and water (oil) and some other factors. For example, values measured in air are typically several orders of magnitude lower than the values measured above aqueous solutions. The substance with a high odour threshold value must be present in foods in higher concentrations than substance with a low odour threshold value, otherwise its smell is imperceptible. The measure of whether the substance acts as an odour-active substance is its odour unit, its actual concentration divided by odour threshold concentration. 

The presence of lipids, proteins, carbohydrates and other substances significantly influences the retention of aromatic compounds in foods and has an effect on their odour intensity and quality (e.g. the odour threshold values of non-polar substances measured in water are usually lower than the values measured in... 

Table 8.33 displays the odour threshold values of some intensely odoriferous substances. The odour threshold values of selected common odoriferous substances are Hsted in Table 8.34 and Table 8.35. 

The proximity of results obtained by OSME and GC- SNIF might be justified by van Ruth s (42) observation that the number of assessors perceiving an odour correlated significantly with odor intensity scores [.. . ] indicating that the number of assessors is a sufficient measure of the odour intensity. When comparing NIF values and odor intensities of all representative odorants perceived in three different wines, Bernet also found a good linear relationship between both variables (Fig. 7) (36). 

The input value of the dispersion model represents the odour load as established by a psychophysical experiment. The experiment relates a human sensation to a physical quantity. The human sensation to be recorded usually encompasses questions concerning the detectability, the intensity or the quality of the odour. In the case of odour pollution, the physical quantity is often expressed as the dilution number or the relative concentration. 

The curry leaf plant is highly valued for its characteristic aroma and medicinal value (Philip, 1981). A number of leaf essential oil constituents and carbazole alkaloids have been extracted from the plant (Mallavarapu et al., 1999). There are a large number of oxygenated mono- and sesquiterpenes present, e.g. c/s-ocimene (34.1%), a-pinene (19.1%), y-terpinene (6.7%) and P-caryophyllene (9.5%), which appear to be responsible for the intense odour associated with the stalk and flower parts of curry leaves (Onayade and Adebajo, 2000). In fresh bay leaves, 1, 8-cineole is the major component, together with a-terpinyl acetate, sabinene, a-pinene, P-pinene, P-elemene, a-terpineol, linalool and eugenol (Kilic et al., 2004). 

The initial EC regulation (EC Council, 1991) establishes 6.5 as the minimum score to classify an oil as extra virgin. The other categories are, from a sensory point of view, identified by smaller figures where the values depend on the degree of defective odour perceived with high intensity, such as rancid, musty, fusty, muddy sediment, winey attributes. Table 2.5 summarizes the scores for the different categories. 

As can be seen the pyrolysis gas contains mainly hydrogen, methane and other hydrocarbons. In our case the yield was 167 kg for each ton of used tyres. The average calorific value was determined to be approx. 34.500 kJ/m3. The odour was specific and intense. 

On the average 1 ton of used tyres yields 468 kg of condensate having a typical and intense odour and a calorific value of 40. 000 kJ/kg. The flash point is near 8°C. For further details please refer to table 2,... 

The oil is generally distilled from the waste shavings from lead-pencil manufacture, which are usually plentiful when the pencils are cut from logs. When thin sawn boards are imported and used, the refuse is much smaller in amount, and the price naturally rises. Owing to the methods of distillation, the oil manufoctured from pencil waste is of less value to perfumers than normally prepared oil. The yield of oil obtained varies from 2-5 to 5 per cent. Juniperus virginiana occurs over a ve wide area in America, and some of the finest oil is obtained from the Florida cedar. This oil is one of those which are indispensable in certain classes of perfumery, especially in fine soap-making, where intensely sweet odours are not required. The wood in fine powder finds its way into much of the incense and similar preparations used either for ceremonial or fumigating purposes. 

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