Butyric acid flavoring from

Several aliphatic carboxylic acids have been known for centuries, and their common names reflect their historical sources. Formic acid was extracted from ants formica in Latin. Acetic acid was isolated from vinegar, called acetum ( sour ) in Latin. Propionic acid was considered to be the first fatty acid, and the name is derived from the Greek protos pion ( first fat ). Butyric acid results from the oxidation of butyraldehyde, the principal flavor of butter butyrum in Latin. Caproic, caprylic, and capric acids are found in the skin secrehons of goats caper in Lahn. The names and physical properties of some carboxylic acids are listed in Table 20-1. 

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. 

These acids are found ready-made in nature in great numbers. Some of them occur as free acids (citric acid, tannic acid, malic acid), others as esters (products of acids and alcohols, such as fats and oils and the flavors of many fruits and the odors of many flowers). Still other of these organic acids are produced by the action of bacteria (acetic acid from wine or cider, lactic acid when milk turns sour, butyric acid in rancid hutter). 

Some Effects of Lipolysis. The most serious effect of lipolysis is the appearance of the so-called rancid flavor which becomes detectable in milk when the ADV exceeds 1.2-1.5 mEq/liter (Brathen 1980). The fatty acids and their soaps, which are thought to be implicated in the rancid flavor, have been studied in an effort to assess the role of the individual acids in the overall rancid flavor picture. Scanlan et al (1965) reported that only the even-numbered fatty acids from C4 to Cl2 account for the contribution of fatty acids to the flavor, but that no single acid exerts a predominating influence. Another study has implicated the sodium and/or calcium salts of capric and lauric acids as major contributors to the rancid flavor (Al-Shabibi, et al. 1964). Butyric acid, assumed to be the compound most intimately associated with the flavor, was not singled out in either study as being especially involved. 

Hydrolytic rancidity flavor defects in Swiss, brick, and Cheddar cheeses have been linked to high concentrations of individual short chain free fatty acids (Woo et al 1984). Lipases from psychrotrophic bacteria have been implicated in causing rancidity in cheese (Cousin 1982 Kuzdzal-Savoie 1980), although most starter streptococci and lactobacilli isolated from cheese are also capable of hydrolyzing milk fat (Paulsen et al. 1980 Umemoto and Sato 1975). Growth of Clostridium tyrobutyricum in Swiss cheese causes the release of butyric acid and subsequent rancid-off flavors (Langsrud and Reinbold 1974). The endogenous lipoprotein lipase is also responsible for hydrolytic rancidity in nonpasteurized milk. 

In addition to positive aspects, numerous flavor and textural defects may be associated with the fat phase of ice cream. Such flavor defects are usually related to either autoxidation of the fat, resulting in oxidized flavors (cardboardy, painty, metallic) or, especially in the case of milk-fat, lipolysis of free fatty acids from triglycerides by the action of lipases (referred to as hydrolytic rancidity). A significant content of free butyric acid gives rise to very undesirable rancid flavors. These defects tend to be present in the raw ingredients used in ice cream manufacture, rather than promoted by the ice cream manufacturing process itself. However, processing... 

The flavor thresholds for the individual fatty acids are quite different in butter and in milk. Whereas in milk, Cio o and Ci2 o acids are most significant to rancid flavor, in butter C4 o and C o are of most interest since they have much lower flavor thresholds in fat than do the longer-chain acids (Patton, 1964). The reported thresholds of the C4 o to Ci2 o acids added singly or in pairs to butter are shown in Table 15.3, together with the theoretical amounts for an increase in ADV of 0.1 meq/100 g fat. From these data, it is evident that a low level of lipolysis in butter produces sufficient butyric acid to exceed its flavor threshold and to impart a rancid flavor. Thus, measurement of C o, C(, o and Cg o gives the best indication of hydrolytic rancidity in butter (McNeill et al., 1986). 

Systematic names for carboxylic acids use the -oic acid suffix, but historical names are commonly used. Formic acid was first isolated from ants, genus Formica. Acetic acid, found in vinegar, gets its name from the Latin word for sour (acetum). Propionic acid gives the tangy flavor to sharp cheeses, and butyric acid provides the pungent aroma of rancid butter. 

Cheese/hutter flavor. Pregastric lipases, have, been used for years to intensify flavor in Menzyme-modified cheese , and for an intensified butter flavor in lipolyzed butter. Generally the fatty acid residues that need to be split off (to generate the right flavor) are the short chain fatty acids, especially the C to C-jq acids typical of Italian cheeses. The butyric acids are produced from butterfat more specifically by newly developed lipases (really esterases) from Mucor meihei and a very new one, from Aspergillus oryzae, especially for cheddar cheese flavor development. The latter enzyme is marketed under the name Flavor Age (4). Flavors produced in this manner are used widely in cheese-flavored snack foods the value of the intensified cheese flavors is on the order of 50 million, but the. value of the enzymes employed is only about 2-3 million. 

The trivial names that indicate the initial source of fatty acids are used more often than the lUPAC names in the industry. For example, butyric acid is a major component of butter flavor, palmitic acid comes from palm kernel, and oleic acid from olives. 

C. Q. butyric Cg.Q, caproic Cg.Q, caprylic Cjqq, capric). Butyric acid is found exclusively in the milk fat of ruminant animals and is responsible for the rancid flavor produced when it is released from triglycerides by hpase action. Saturated fatty acids such as Cj4.q, Cjg.Q, and Cjg.Q make up two thirds of milk fatty acids. Oleic acid (C18 l) is the most abundamt unsaturated fatty acid in milk. Although the cis geometry is the one most commonly found in nature, 5% of all unsaturated bonds are in the trans position as a result of rumen hydrogenation. 

While dairy products may become lipolyzed due to indigenous enzymes, the lipases may also be from outside sources. Bacterial activity, spices, and some fruits contain lipases that may attack the triglycerides of milk. It is relevant that different lipases (different sources) will have a different preference for lipolysis of fatty acids. MiUc lipase and other ruminant sources of lipases tend to preferentially lyse butyric acid from triglycerides. Lipases from Pseudomonas fluorescens and all porcine lipases have little preference for short chain fatty acids. Lipases from molds and Chromobacterium viscosum produce less butyric acid but more capric acid [108]. Lipases that preferentially lyse the short chain fatty acids have a greater impact in the production of off-flavors than do those lipases that lyse the longer chain fatty. 

Low-molecular-weight carboxylic acids are difficult to extract from aqueous solutions using SPME techniques. Formic through butyric acids are miscible in water, and even caprylic acid (Cs) is soluble to the extent of 68 mg/100 g (7). The low capacity factors of carboxylic acids to nonpolar phases used in capillary gc columns lead to severe fronting of acid peaks, which often can be used to identify their presence in mixtures with other flavor compounds. The same phenomenon also has an effect on the absorption of acids by SPME phases. It is possible to enhance their extraction by SPME fibers, however. Figure 3 shows the relative extraction efficiencies for several carboxylic acids, each at a concentration of 10 ppm in water. The results show the effectiveness of headspace extractions using both the 85- a,m polyacrylate and lOO-pm polydimethylsiloxane fibers alone, and after the addition of 25% NaCl to the solutions. With the excep-... 

Butyric fatty acid is specific for milk fat of ruminant animals and is responsible for the rancid flavor when it is cleaved from glycerol by lipase action. 

Fruity flavor in dairy products is the result of ethyl ester formation, usually catalyzed by esterases from psychrotrophic or lactic acid bacteria. Ester formation by P. fragi involves liberation of butyric and ca-proic acids from the one and three positions of milk triglycerides and the subsequent enzymatic esterification of these fatty acids with ethanol (Hosono et al. 1974 Hosono and Elliott 1974). Consequently, among the esters formed, ethyl butyrate and ethyl hexanoate predominate. Pseudomonas-produced fruity flavor can occur in fluid milk, cottage cheese, and butter. 

Fruity flavor in Cheddar cheese is also associated with high levels of ethyl butyrate and ethyl hexanoate (Bills et al. 1965). However, this defect is usually caused by esterase activity from lactic acid bacteria, especially S. lactis and S. lactis subsp. diacetylactis (Vedamuthu et al. 1966). Fruity-flavored cheeses tend to have abnormally high levels of ethanol, which is available for esterification (Bills et al. 1965). Streptococcal esterase activity in cheese is affected by the level of glutathione, which suggests a dependence on free sulfhydral groups for activity (Harper et al. 1980). 

Hydrolytic rancidity results from the hydrolytic degradation of milk lipids. The hydrolysis is catalyzed by lipases and produces free fatty acids (FFAs), some of which have a low flavor threshold and can cause unpleasant flavors in milk and milk products. These flavors are variously described as rancid, butyric, bitter, unclean, soapy or astringent. The lipases involved are of two types indigenous milk enzyme(s) and enzymes of microbial origin. 

The fine flavor and bouquet result from the secondary constituents of the brandy and are dependent upon a number of factors, principally raw materials, operating methods, aging, etc. The secondary constituents consist of various esters (acetic, butyric, oenanthic, valerianic), acetic acid, volatile oils, tannin, fixed acid and coloring matter. Ethyl pelargonate (oenanthic ester) and other volatile constituents are thought to be mainly responsible for the flavor. 

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