Cheddar flavor

Methanethiol has been found to be correlated with the development of Cheddar cheese flavor by Manning and coworkers (37, 39, 40), and both nonenzymic (22) and enzymic generation of methanethiol have been proposed as the source of this compound in Cheddar cheese (46). Although the correlation of methanethiol to Cheddar flavor appears statistically valid, difficulties have been encountered in explaining the nature of its flavor-conferring properties in cheese. In addition, uniform production of methanethiol is difficult to achieve commercially, and the rate of its natural formation in accelerated-ripening may not be suitable for achieving typical Cheddar flavors (47, 48). 

Table I, and reflect the Cheddar flavor intensity correlation reported by Manning and coworkers (37). In addition to methanethiol, peaks for dimethyl disulfide were quite large in the aged Cheddar and the Colby cheese headspace profiles, but very little of this compound was found in the mild Cheddar sample.

Of these, Manning (40) has reported that pentan-2-one, acetone, methanol along with methanethiol correlate best with Cheddar flavor intensity and Cheddar quality. 

The extremely elusive nature of the chemical basis of Cheddar-like flavors supports the hypothesis that an unstable aroma compound is involved in the flavor of Cheddar cheese, and this view deserves thorough investigation. The circumstantial evidence in favor of the existence of a Cheddar-like aroma also includes considerations relating to the sensitivity of Cheddar flavor to heat and oxygen, and the fact that the redox of cheese is quite low. Additionally, sulfury or sulfide-like defects as well as brothy flavor-like defects are often encountered in Cheddar cheeses of various compositions and origin. These flavors could reflect either production of excessive amounts of certain sulfur compounds or the absence of certain essential compounds that are initially required to allow formation of a Cheddar compound. While attempts to date have not resulted in the isolation of such a compound, this could reflect the very unstable nature of the proposed compound. Other similar circumstances appear to occur in freshly roasted coffee and nuts where transient... 

The very small peptides in the UF permeate have not yet been identified. A number of authors (Aston and Creamer, 1986 Cliffe et al., 1993 Engels and Visser, 1994) have shown that the very small peptides (<500 Da) make a significant contribution to Cheddar flavor therefore, identification of the small peptides should prove interesting. 

By a wide margin, Cheddar is the most popular cheese flavor in North America. Its flavor is described as sweet, buttery, aromatic, and walnut, yet there is no general consensus among flavor chemists about the identity of individual compounds or groups of compounds responsible for Cheddar flavor. Reinec-cius and Milo (80) concluded that butyric acid, acetic acid, methional, 2,3-butanedione, and homofuraneol (5-ethyl-4-hydroxy-2-methyl-(2//)-furan-3-one) are primary contributors to the pleasant mild flavor of Cheddar cheese. Important contributors to Cheddar aroma are 2,3-butanedione, dimethyl sulfide/trisulfide, and methanethiol (80). 

Since antiquity, animal milks have been converted by empirical processes to a wide variety of cheeses. With the development of microbiology as a scientific discipline, the critical role of microorganisms - bacteria, fungi, yeasts - in cheese began to be understood. Today, more than 650 cheese types are recognized and the flavor(s) of cheese has (have) now been investigated for more than a century.33 Typically, the situation is complex and the literature is enormous. For instance, more than 200 volatiles occur in Cheddar cheese. In a listing of 58 of these volatiles, 7 are sulfur compounds dimethyl sulfide (DMS),... 

After the curd and whey are physically separated and the optimum pH level is reached, the curd is salted. Salt improves the flavor of cheese, retards microbial metabolism, and helps expel moisture from the curd. Salt is either added directly to the curd (Cheddar, Colby) or the preformed block of cheese is placed in a brine solution (almost all other cheese types). 

Excessive or insufficient acid development during manufacture can produce variability in the moisture content of cheese and defects in flavor, body, texture, color, and finish (Van Slyke and Price 1952). The rate of lactose fermentation varies with the type of cheese, but the conversion to lactic acid is virtually complete during the first weeks of aging (Van Slyke and Price 1952 Turner and Thomas 1980). Very small amounts of lactose and galactose may be found in cheese months after manufacture. (Huffman and Kristoffersen 1984 Turner and Thomas 1980 Harvey et al. 1981 Thomas and Pearce 1981). Turner and Thomas (1980) showed that the fermentation of residual lactose in Cheddar cheese is affected by the storage temperature, the salt level in the cheese and the salt tolerance of the starter used. 

Shahani 1971). There is still considerable debate over the contribution of fat and its breakdown products to flavor in Cheddar cheese (Law 1984 Aston and Dulley 1982). 

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. 

Aston, J. W. and Dulley, J. R. 1982. Cheddar cheese flavor. Aust. J. Dairy Technol. 37, 59-64. 

During cheese ripening, proteases associated with starter culture organisms are released into cheese after cell lysis (Law et al. 1974). The proteolytic activity associated with lysed lactic streptococci is necessary for proper flavor development in Cheddar and other cheese varieties. The role of streptococcal proteases and peptidases appears to be production of flavor compound precursors such as methionine and other amino acids, rather than direct production of flavor compounds (Law et al. 1976A). Additional discussion of cheese ripening is presented in Chapter 12. 

Micrococci comprise approximately 78% of the nonlactic bacteria in raw milk Cheddar cheese (Alford and Frazier 1950). The proteolytic system of Micrococcus freudenreichii functions optimally at 30 °C and at a pH near neutrality (Baribo and Foster 1952). An analysis of pro-teinases present in 1-year-old Cheddar cheese indicates that micrococci may contribute to proteolytic activity (Marth 1963). Proteolytic micrococci also contribute to the ripening of surface-ripened cheeses such as brick and Camembert (Lenoir 1963 Langhus et al. 1945). Micrococcal proteases probably contribute to development of ripened cheese flavor when ripening temperatures are above 10°C (Moreno and Kosikowski 1973). This effect results from degradation of /3-casein. 

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). 

Dacre, J. C. 1953. Cheddar cheese flavor and its relation to tyramine production by lactic acid bacteria. J. Dairy Res. 20, 217-223. 

Vedamuthu, E. R., Sandine, W. E. and Elliker, P. R. 1966. Flavor and texture in Cheddar cheese. I. Role of mixed strain lactic starter cultures. J. Dairy Sci. 49, 144-150. 

Yates, A. R., Irvine, O. R. and Cunningham, J. D. 1955. Chromatographic studies on proteolytic bacteria in their relationship to flavor development in Cheddar cheese. 

Reiter, B. and Sharpe, M. E. 1971. Relationship of microflora to the flavor of Cheddar cheese. J. Appl. Bacterial 34, 63-80. 

None Skim milk Chocolate milk Plain yogurt (lowfat) Cottage cheese (4%) Chocolate milk shake Fruit flavored yogurt Evaporated milk Milk (2%) Half Half cream Ice cream (light) Whole milk Sherbet Vanilla ice cream Sour cream Swiss cheese Cheddar cheese Cream cheese American cheese Butter... 

Free amino acids are further catabolized into several volatile flavor compounds. However, the pathways involved are not fully known. A detailed summary of the various studies on the role of the catabolism of amino acids in cheese flavor development was published by Curtin and McSweeney (2004). Two major pathways have been suggested (1) aminotransferase or lyase activity and (2) deamination or decarboxylation. Aminotransferase activity results in the formation of a-ketoacids and glutamic acid. The a-ketoacids are further degraded to flavor compounds such as hydroxy acids, aldehydes, and carboxylic acids. a-Ketoacids from methionine, branched-chain amino acids (leucine, isoleucine, and valine), or aromatic amino acids (phenylalanine, tyrosine, and tryptophan) serve as the precursors to volatile flavor compounds (Yvon and Rijnen, 2001). Volatile sulfur compounds are primarily formed from methionine. Methanethiol, which at low concentrations, contributes to the characteristic flavor of Cheddar cheese, is formed from the catabolism of methionine (Curtin and McSweeney, 2004 Weimer et al., 1999). Furthermore, bacterial lyases also metabolize methionine to a-ketobutyrate, methanethiol, and ammonia (Tanaka et al., 1985). On catabolism by aminotransferase, aromatic amino acids yield volatile flavor compounds such as benzalde-hyde, phenylacetate, phenylethanol, phenyllactate, etc. Deamination reactions also result in a-ketoacids and ammonia, which add to the flavor of... 

Aston, J. and Creamer, L. K. (1986). Contribution of the components of water-soluble fraction to the flavor Cheddar cheese. NZ Dairy Sci. Technol. 21, 229-248. 

Cliffe, A. J., Marks, J. D., and Mulholland, F. (1993). Isolation and characterization of nonvolatile flavors from cheese, peptide profile of flavor fractions from Cheddar cheese, determined by reverse phase high-performance chromatography. Int. Dairy. ]. 3,379-387. 

Manning, D. J. (1978). Cheddar cheese flavor studies I. Production of volatiles and development of flavor during ripening.. Dairy Res. 45,479-490. 

Subramanian, A. (2009). Monitoring flavor quality, composition and ripening changes of Cheddar cheese using Fourier-transform infrared spectroscopy. PhD Thesis, The Ohio State University, p. 121. 

Subramanian, A., Harper, W. J., and Rodriguez-Saona, L. E. (2009a). Cheddar cheese classification based on flavor quality using a novel extraction method and Fourier transform infrared spectroscopy. J. Dairy Sci. 92, 87-94. 

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