Odor and Taste

Section 7 8 Both enantiomers of the same substance are identical m most of then-physical properties The most prominent differences are biological ones such as taste and odor m which the substance interacts with a chiral receptor site m a living system Enantiomers also have important conse quences m medicine m which the two enantiomeric forms of a drug can have much different effects on a patient... 

J. R. Bayhs, Elimination of Taste and Odor in Water, McGraw-Hill Book Co., New York, 1935, pp. 304—307. 

Toxicity. Sodium fluoroacetate is one of the most effective all-purpose rodenticides known (18). It is highly toxic to all species of rats tested and can be used either in water solution or in bait preparations. Its absence of objectionable taste and odor and its delayed effects lead to its excellent acceptance by rodents. It is nonvolatile, chemically stable, and not toxic or irritating to the unbroken skin of workers. Rats do not appear to develop any significant tolerance to this compound from nonlethal doses. However, it is extremely dangerous to humans, to common household pets, and to farm animals, and should only be used by experienced personnel. The rodent carcasses should be collected and destroyed since they remain poisonous for a long period of time to any animal that eats them. 

Pish protein concentrate and soy protein concentrate have been used to prepare a low phenylalanine, high tyrosine peptide for use with phenylketonuria patients (150). The process includes pepsin hydrolysis at pH 1.5 ptonase hydrolysis at pH 6.5 to Hberate aromatic amino acids gel filtration on Sephadex G-15 to remove aromatic amino acids incubation with papain and ethyl esters of L-tyrosine and L-tryptophan, ie, plastein synthesis and ultrafiltration (qv). The plastein has a bland taste and odor and does not contain free amino acids. Yields of 69.3 and 60.9% from PPG and soy protein concentrate, respectively, have been attained. 

Calcium—zinc stabilizers are used in both plasticized PVC and rigid PVC for food contact where it is desired to minimize taste and odor characteristics. AppHcations include meat wrap, water botdes, and medical uses. 

Taste and Odor. The measurement of taste and odor is somewhat subjective and depends on the personal judgements of individuals. Panels of not less than five observers, and preferably more than ten, are used. The sample is diluted with odor-free water until a ratio at which the odor is just perceptible is determined this ratio is called the threshold odor number (TON). A similar method is used to detect a distinct taste in water (see Flavor characterization). ... 

The goal of filtration in the modem municipal treatment plant is a maximum of 0.1 ntu (nephelometric turbidity unit), which ensures a sparkling, clear water (8). Freedom from disease organisms is associated with freedom from turbidity, and complete freedom from taste and odor requites no less than such clarity. The National Interim Primary Drinking Water Regulations (NIPDWR) requite that the maximum contaminant level for turbidity at the point of entry into the distribution system be 1.0 ntu unless it can be shown that levels up to 5 ntu do not interfere with disinfection, interfere with the maintenance of a chlorine residual in the distribution system, nor interfere with bacteriological analyses. 

Taste and Odor Control. Tastes and odors in surface waters result from the action of biological organisms, eg, algae, or from various minerals, pollution by industry, domestic seepage, or agriculture. Groundwaters may have taste and odor if they are polluted or if they contain gases, eg,... 

H2S or CH the latter always contains associated impurities that have taste and odor. Removal of these gases can be accompHshed by adsorption (qv) with activated carbon (qv) oxidation with chlorine, potassium permanganate, or o2one or aeration. 

Sweeteners. The sweeteners (qv) used in carbonated beverages may be either nutritive or noimutritive. The quaUty of the sweetener is one of the most important parameters affecting the overall quaUty of the beverage. Organoleptic profile (taste and odor), solubiUty, microbial stabiUty, and temperature stabiUty are important quaUty parameters. 

Carbon dioxide used in carbonated beverages must be food-grade and must meet the Compressed Gas Association commodity specifications for carbon dioxide. In addition, carbon dioxide is tested for purity, taste, and odor before being used in the production of beverages. 

The first application of chlorine in potable water was introduced in the 1830s for taste and odor control, at that time diseases were thought to be spread by odors. It was not until the 1890s and the advent of the germ theory of disease that the importance of disinfection in potable water was understood. Chlorination was first introduced on a practical scale in 1908 and then became a common practice. 

Diatomaceous earths may resemble the forms of the charcoals. The earths are primarily filter aids, precoats or adsorbents, the hmction of the filter medium being secondary. Fuller s earth and clays are used for decoloring applications diatomaceous earths are used for clarification. The adsorbtivity of diatomaceous earth works in the same fashion as activated carbon, but isotherms (affinity) for many chemical species like the hydrocarbons is weaker. For this reason, activated charcoal or carbon is much preferred in wastewater treatment applications expecially when taste and odor issues are priorities. 

Potable water treatment Granular activated carbons (GAC) installed in rapid gravity filters Removal of dissolved organic contaminants, control of taste and odor problems... 

The most common application of carbon adsorption in municipal water treatment is in the removal of taste and odor compounds. Figure 12 provides an example of a process flow diagram for a municipal water treatment plant. In this example water is pumped from the river into a flotation unit, which is used for the removal of suspended solids such as algae and particulate matter. Dissolved air is the injected under pressure into the basin. This action creates microbubbles which become attached to the suspended solids, causing them to float. This results in a layer of suspended solids on the surface of the water, which is removed using a mechanical skimming technique. Go back to Chapter 8 if you need to refresh your memory on air flotation systems. 

Figure 13.Example of a municipal water treatment plant for taste and odor control.

Chlorine dioxide uses expanded rapidly in the industrial sector. In 1944, chlorine dioxide was first applied for taste and odor control at a water treatment plant in Niagara Falls, New York. Other water plants recognized the uses and benefits of chlorine dioxide. In 1958, a national survey determined that 56 U.S. water utilities were using chlorine dioxide. The number of plants using chlorine dioxide has grown more slowly since that time. 

At present, chlorine dioxide is primarily used as a bleaching chemical in the pulp and paper industry. It is also used in large amounts by the textile industry, as well as for the aching of flour, fats, oils, and waxes. In treating drinking water, chlorine dioxide is used in this country for taste and odor control, decolorization, disinfection, provision of residual disinfectant in water distribution systems, and oxidation of iron, manganese, and organics. The principal use of chlorine dioxide in the United States is for the removal of taste and odor caused by phenolic compounds in raw water supplies. 

The process has two main sources of waste water. These are the condensate streams from the steam strippers. The principal pollutant in both wastewater streams is phenol. Phenol is of concern primarily because of its toxicity, oxygen depletion, and turbidity. In addition, phenol can cause objectionable taste and odor in fish flesh and potable water. 

Ozone is more effective than chlorine in deactivating poliovirus, Cryptosporidium parvum, Giardia lamblia, and other protozoa. It also improves the color, taste, and odor of water dramatically. However, since no residual amount remains, it is always necessary to add a small amount of a more stable disinfectant as well (sodium hypochlorite, chlorine dioxide, etc.). 

Allicin is responsible for the distinctive taste and odor of garlic Its simple formula is C6H10O2S. How many grams of sulfur can be obtained from 25.0 g of allicin ... 

The hypochlorous acid, HCIO, formed by this reaction is a powerful oxidizing agent (E a = +1.630 V) it kills bacteria, apparently by destroying certain enzymes essential to their metabolism. The taste and odor that we associate with chlorinated water are actually due to compounds such as CH3NHC1, produced by the action of hypochlorous acid on bacteria. 

Such definitions imply that there is a reliable test for rancidity, but this is not the case. The difficulties are centered about the fact that in the final analysis, rancidity must be detected through organoleptic observation, which is subject to all the weaknesses inherent in a test involving personal judgment. As was pointed out in a recent discussion (S), these weaknesses include variabilities in the taste and odor sensitivities of persons in the same or different laboratories, their previous taste experiences, the prevailing condi-... 

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