Limited odor unit

Tamura et al. (this volume) discuss the suitability of the detection threshold and the recognition threshold in determining the limited odor unit for characterizing citrus aroma quality. 

Table IV. Limited Odor Unit Value of Volatiles in Navel Orange ...

On the basis of the odor activity value (OAV) concept, only a limited number of volatile components are sensorially relevant in a given foodstuff (Grosch, 1994). Teranishi et al. (1996) also presented a computer-assisted correlation of chromatographic and sensory data in food aromas. In a bar graph were shown the logarithms of the concentrations and of the odor units of the individual constituents of the aroma. The representation shows clearly the constituents present above the threshold values and therefore the most useful for the aroma. 

Early detection of a chemical leak is necessary in order to limit its effect on people and the environment. The most fundamental method for detecting a chemical release is the systematic patrol of operating units by personnel trained to recognize potentially hazardous vapors using odor or visual observations. The frequency and scope of the patrols will vary with the nature of the process equipment and materials however, every facility should have documented patrol procedures in place. 

Ethylene (Ethene or Elayl), H2C CH2 mw 28.05 colorless, flammable, dangerous to handle gas with characteristic sweet odor and taste sp gr 0.975 (air = 1.0), mp —169.4°, bp —103.8°, flash p —136°C explosive limits in air, % by vol, lower 3.0 upper 34.0 si sol in w, more in ale sol in eth. Ethylene is a major component of petroleum refinery gas from cracking units, and is sometimes recovered therefrom by distillation or other means. Some pure ethylene is produced by passing hot ethanol vapors over a catalyst, such as activated alumina (Ref 4). Its laboratory prepn consists of heating ethanol in definite proportions with sulfuric acid of certain concns. By using a 90% acid and 90% ale, ethylene can be produced in a regular stream at a yield of 84 to 85% of theory (Ref 2). 

The odorant concentrations remained within the relative unit ranges tested in the actual experiment. The sensory attributes could act as constraints. For instance, one goal was determination of the optimum acceptability level, with the perception of overall odor intensity lying between prescribed limits of intensity. 

Lower dose treatments, often referred to as pasteurization doses, have shown much more promise. In particular, doses sufficiently low to cause no significant odor and flavor change in the food are adequate to eliminate the hazards to health associated with salmonella and nematode contamination. For example, the irradiation of frozen meat, whole egg and egg products used in baking, and high protein animal foodstuffs is under active investigation as a means of elimination of salmonellae. At the moment, however, this cannot be classed as an industrial application, since only a few tons have been irradiated in pilot experiments.The shelf-life of white fish kept on ice has been considerably extended by small doses of radiation, and in the United States a full-scale plant for the irradiation of fish has recently been completed. Fish remain an underused protein resource available for the underdeveloped countries, and a big expansion in fish consumption is likely if the world s protein requirements are to be met. Inevitably, the development of fish resources must go hand in hand with satisfactory transportation in view of the relatively limited shelf-life... 

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