Cheddar volatile compounds

Several of the smaller volatile compounds formed from the catabolism of products of primary proteolysis (e.g., amino acids) can be determined by GC. The development of capillary columns and interfacing GC with MS has noticeably increased the sensitivity of this analysis. Over 200 volatile compounds have been identified in Cheddar cheese. A list of several of these compounds can be found elsewhere (Fox et ah, 2004a Singh et ah, 2003). The instrumental techniques available for the characterization of cheese aroma were also discussed recently (Le Quere, 2004 Singh et al., 2003). 

Based on a survey of the published literature, Maarse and Vischer (1989) listed 213 volatile compounds that had been identified in 50 studies on Cheddar these included 33 hydrocarbons, 24 alcohols, 13 aldehydes, 17 ketones, 42 acids, 30 esters, 12 lactones, 18 amines, 7 sulfur compounds, 5 halogens, 6 nitriles and amides, 4 phenols, 1 ether, and 1 pyran. The concentrations of many of these compounds were reported. The principal volatile compounds identified in Cheddar are listed in Table VII. 

SIXTV-ONE VOLATILE COMPOUNDS WHICH HAVE BEEN IDENTIFIED IN CHEDDAR CHEESE"... 

Scarpellino, R., and Kosikowski, F. V. (1962). Evolution of volatile compounds in ripening raw and pasteurized milk Cheddar cheese observed by gas chromatography. J. Dairy Sci. 45, 343-348. 

W. Yang and D. Min, Dynamic headspace analysis of volatile compounds of Cheddar and Swiss cheese during ripening, J. Food Sci. 59 1304 (1994). 

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),... 

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... 

Quantitative studies on the enzymatic generation of methanethiol from methionine showed that methioninase obtained from Pseudomonas putida could be used for the development of flavors. Reactions carried out under anaerobic conditions yielded only methanethiol while aerobic conditions favored conversion of substantial amounts of methanethiol to dimethyl disulfide. Incorporation of free or fat-encapsulated methionine/methioninase systems into Cheddar cheeses resulted in the formation of volatile sulfur compounds, including carbon disulfide, and accelerated rates of development of aged Cheddar-like flavors. Methanethiol, when present alone, was observed not to cause the true, Cheddar-like flavor note in experimental cheeses. 

While the relationship of headspace concentrations of methanethiol and other volatiles to their actual concentrations in cheese remains to be established, headspace concentrations of volatile sulfur compounds appear appropriate to assess relative effects of various treatments (64). A baseline of information on methanethiol concentrations found in cheeses manufactured in the University of Wisconsin Dairy Plant was initially developed to serve as a magnitude guide for the current trials as well as for comparative purposes with those published for Cheddar cheese by others (37, 40, 48). Concentrations of methanethiol are shown in... 

Compounds responsible for cheese aroma are volatile. While some preliminary work on the volatile constituents of cheese was done before 1960, e.g., short chain fatty acids and amines, significant progress was not possible until the development of GC in the 1950s. GC was first applied to the study of Cheddar cheese volatiles by Scarpellino and Kosikowski (1962) and McGugan and Howsam (1962), who used vacuum distillation and cold... 

A number of intra- and intervarietal comparisons of cheese volatiles have been published. An early example is that of Manning and Moore (1979) who analyzed head-space volatiles of nine fairly closely related varieties considerable intervarietal differences were evident but the four samples of Cheddar also differed markedly. The intensity of cheese flavor was reported to be related to the concentration of sulfur compounds (peaks 1 and 2) 2-pentanone was also considered to be important for Cheddar cheese flavor. 

A more comprehensive study on Cheddar, Gouda, Edam, Swiss, and Parmesan (total of 82 samples) was reported by Aishima and Nakai (1987). The volatiles were extracted by CH2CI2 and analyzed by GC. More than 200 peaks were resolved in every chromatogram, 118 of which were selected as variables for discriminative analysis. Expression of the area of each of the 118 peaks as a percentage of total chromatogram area clearly permitted classification of the five varieties. The compounds likely to be responsible for the characteristic flavor of each variety were not discussed. 

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