Perfume rancidity

The odor threshold values for methyl ketones are substantially higher than those for aldehydes (cf. Tables 3.32 and 3.47). Nevertheless, they act as aroma constituents, particularly in flavors of mold-ripened cheese (cf. 10.2.8.3). However, methyl ketones in coconut or palm oil or in milk fat provide an undesirable, unpleasant odor denoted as perfume rancidity . 

Nitrobenzene, CgH5N02, also known as oil of mirbane, is an artificially prepared benzene derivative, having a coarse, but powerful odour resembling that of oil of almonds. Its coarse odour renders it quite unsuitable for fine perfumery, but it finds considerable employment in the manufacture of cheap soaps, polishes, and other articles where more or less rancid fats are used, as it covers the bad odour of the fat and gives the product a coarse almond perfume. 

Phenylalanine very strong, hyacinth(35) rancid caramel, stinging smell, unpleasant(36) very objec-violets(37) rose tionable(36) perfume(39) pleasant sweet caramel(36) unpleasant sweet caramel(36)... 

Oxidation is also the main cause of perfume instability in poor-quality toilet soaps here it is caused by the fatty acid peroxides formed at the stage of incipient rancidity. Perfumes may to some extent be protected against oxidation by the incorporation of 1% to 2% of an antioxidant such as BHT (butylated hydroxy toluene) into the perfume oil. 

This is quite undesirable in a perfume because many carboxylic acids have objectionable odors. For example, the sharp, penetrating odor of vinegar is due to acetic acid, butanoic acid (butyric acid) smells like rancid butter, and 2-methylpropanoic acid (isobutyric acid) is a component of sweat. A common name for hexanoic acid is caproic acid, derived from the Latin word caper, which means goat. If you have ever been around goats, perhaps you can imagine the odor of hexanoic acid. 

Aldehydes and ketones are also important components of many fragrances and flavors. For example, butanal (butyraldehyde) is used to impart a buttery flavor to margarine and other foods. Because aldehydes are slowly oxidized to carboxylic acids by the oxygen of air, it is readily apparent how the odor of rancid butter arises. Although a-pentylcinnamaldehyde does not occur naturally, it has been found to have a powerful jasmine odor and is used in many perfumes and soaps, a-lonone is a naturally oc-... 

I ran up to my dainty chamber and laid the cloak by the fire. Immediately, all of Kempe s carefully contrived perfume was blotted out by a terrible smell of excrement and rancid meat. 

Propyl gallate has become widely used as an antioxidant in cosmetics, perfumes, foods, and pharmaceuticals since its use in preventing autoxidation of oils was first described in 1943. It is primarily used, in concentrations up to 0.1% w/v, to prevent the rancidity of oils and fats it may also be used at concentrations of 0.002% w/v to prevent peroxide formation in ether, and at 0.01% w/v to prevent the oxidation of paraldehyde. Synergistic effects with other antioxidants such as butylated hydroxyanisole and butylated hydroxytoluene have been reported. Propyl gallate is also said to possess some antimicrobial properties see Section 10. 

The most successM perfume of all times is Chanel No. 5 , which dates back to the year 1921. It consists of aliphatic aldehydes, with scents reminiscent of rancid... 

Every precaution should he taken to ensure thorough saponification of the soaps intended for blending in shaving soap, otherwise there will Im a tendency to Ijccome discoloured and develop rancidity with age, Hhaving soaps are delicately perfumed, and are placed on the market either in the form of sticks which are cut from the bar of soap as it leaves the compressor, or stamped in flat cakes. 

Carboxylic acids often have strong odors, especially the volatile derivatives. Most common are acetic acid (vinegar) and butyric acid (rancid butter). On the other hand, esters of carboxylic acids tend to have pleasant odors and many are used in perfumes. 

A naturally occurring rancid-tasting saturated fatty acid found in butter (cow and goat) and coconut oil and used eis an intermediary in the manufacture of perfumes and dyes. (Also see FATS AND OTHER LIPIDS.)... 

This type of compounds are able to inhibit reactions promoted by oxygen, thus avoiding the oxidation and rancidity of commonly used fats, oils, waxes, surfactants, perfumes, etc. in cosmetics. They are usually reducing agents and free radical scavengers. 

---