Rancid

Butanoic acid, CH3CH2CH2COOH, colourless syrupy liquid with a strong odour of rancid butter b.p. (sTC. Occurs in butter as the glycerol ester. Prepared by oxidation of 1 -butanol or by the fermentation of sugary or starchy materials by B. subtilis etc. Oxidized... 

It IS hard to find a class of compounds in which the common names of its members have influenced organic nomenclature more than carboxylic acids Not only are the common names of carboxylic acids themselves abundant and widely used but the names of many other compounds are derived from them Benzene took its name from benzoic acid and propane from propionic acid not the other way around The name butane comes from butyric acid present m rancid butter The common names of most aldehydes are derived from the common names of carboxylic acids—valeraldehyde from valeric acid for exam pie Many carboxylic acids are better known by common names than by their systematic ones and the framers of the lUPAC rules have taken a liberal view toward accepting these common names as permissible alternatives to the systematic ones Table 19 1 lists both common and systematic names for a number of important carboxylic acids... 

Ranceite Rancidity Rancimat system Random access memory Random copolymer Random copolymers... 

Fatty acids are susceptible to oxidative attack and cleavage of the fatty acid chain. As oxidation proceeds, the shorter-chain fatty acids break off and produce progressively higher levels of malodorous material. This condition is known as rancidity. Another source of rancidity in fatty foods is the enzymatic hydrolysis of the fatty acid from the glycerol. The effect of this reaction on nutritional aspects of foods is poorly understood andhttie research has been done in the area. 

One disadvantage of fats contained within foodstuffs is the deterioration of the fat through oxidative rancidity. Many consumers find the aroma and flavor of deteriorated fats in foods repulsive, while others are fond of country ham and butter which owe thek aroma and flavor to fat rancidity and other breakdown products. The use of antioxidants (qv) makes such products commercially viable. 

Lipids present in the diet may become rancid. When fed at high (>4-6%) levels, Hpids may decrease diet acceptabiUty, increase handling problems, result in poor pellet quaUty, cause diarrhea, reduce feed intake, and decrease fiber digestion in the mmen (5). To alleviate the fiber digestion problem, calcium soaps or prilled free fatty acids have been developed to escape mminal fermentation. These fatty acids then are available for absorption from the small intestine (5). Feeding whole oilseeds also has alleviated some of the problems caused by feeding Hpids. A detailed discussion of Hpid metaboHsm by mminants can be found (16). 

A few spices, particularly rosemary and sage, are known to act as antioxidants which prevent rancidity due to oxidation in fats and fatty foods. 

Hard baked goods such as cookies and crackers have a relatively low water and high fat content. Water can be absorbed, and the product loses its desirable texture and becomes subject to Hpid rancidity. Packagiag for cookies and crackers includes polyolefin-coextmsion film pouches within paperboard carton sheUs, and polystyrene trays overwrapped with polyethylene or oriented polypropylene film. Soft cookies are packaged in high water-vapor-barrier laminations containing aluminum foil. 

In certain brilliantine compositions, vegetable and animal oils are used as substitutes for mineral oil. In these systems, because of their potential for rancidity, antioxidants must be included. Other alternatives to mineral oils that have found utiHty in brilliantines are the polyethylene glycols which come in a variety of solubiHties and spreading properties. Use of these materials offers the advantage of chemical stabiHty to rancidity. Other additives found in brilliantines to improve their aesthetics include colorants, fragrance, medicated additives, lanolin, and fatty acid esters. 

Antioxidants are used to retard the reaction of organic materials with atmospheric oxygen. Such reaction can cause degradation of the mechanical, aesthetic, and electrical properties of polymers loss of flavor and development of rancidity ia foods and an iacrease ia the viscosity, acidity, and formation of iasolubles ia lubricants. The need for antioxidants depends upon the chemical composition of the substrate and the conditions of exposure. Relatively high concentrations of antioxidants are used to stabilize polymers such as natural mbber and polyunsaturated oils. Saturated polymers have greater oxidative stabiUty and require relatively low concentrations of stabilizers. Specialized antioxidants which have been commercialized meet the needs of the iadustry by extending the useflil Hves of the many substrates produced under anticipated conditions of exposure. The sales of antioxidants ia the United States were approximately 730 million ia 1990 (1,2). 

The effectiveness of antioxidants as preservatives for fats and oils is evaluated by determining the rate of peroxide development using the Active Oxygen Method (AOM) (29). The development of a rancid odor is used to evaluate the stabiUty of food items (Schaal Oven StabiUty test) (30). 

Butter is used in some, usually more expensive, bakery foods, and is prized for its flavor contribution. Fats are used in some products such as pie cmst, croissants, or puff pastry, up to 60%, based on flour. StabiHty of fats and oils in perishable items such as breads, cakes, or pastries is of no consequence because shelf life is so limited that rancidity does not occur. In cookies and crackers, however, stable fats must be used in the formula since prolonged shelf life could lead to product deterioration with fats that develop rancidity. 

The calcium form of EDTA instead of free EDTA is used in many food preparations to stabilize against such deleterious effects as rancidity, loss of ascorbic acid, loss of flavor, development of cloudiness, and discoloration. The causative metal ions are sequestered by displacing calcium from the chelate, and possible problems, such as depletion of body calcium from ingestion of any excess of the free chelant, had it been used, are avoided. 

Another type of chemical change is initiated by light, which may trigger autolytic, that is, free radical (Type I) or singlet oxygen (Type II) reactions. These changes are routinely classified as oxidation. Rancidity in cosmetics, especially those containing unsaturated Hpids, is commonly prevented by use of antioxidants (qv). 

MONITORING RANCIDITY OF FARM MILK USING HEADSPACE SAMPLING... 

Consumer acceptance of milk is strongly determined by its sensory characteristics. The development of off-flavor in milk as a result of lipolysis can reduce the quality of milk. The enzymatic release, by milk lipase, of free fatty acids (FFA) from triglycerides causes a flavor defect in milk described as rancid . Triglycerides in milk contain both long chain and short chain fatty acids, which are released at random by milk lipase. The short chains FFA, like butyric acid, are responsible for the off-flavor. 

Observable Characteristics - Physical State (as normally shipped) Liquid Color. Clear Odor. Rancid, disagreeable strong, penetrating, like rancid butter. 

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