Fried chicken, volatiles

Tang J, Jin QZ, Shen GH, et al. 1983. Isolation and identification of volatile compounds from fried chicken. J Agric Food Chem 31 1287-1292. 

The symmetrical compounds (17, R = R = R ) are formed from an aldehyde and ammonium sulfide (2,29,35) or hydrogen sulfide and ammonia (33), Thialdine (17, R - R - R = Me) is an important aroma compound found in the volatiles of beef broth (48), pressure-cooked meat (49), and fried chicken (50), It is also obtained from acetaldehyde (2,29,37) or from B-mercaptoacetaldehyde and ammonium sulfide (37), In our experiments, it was synthesized as a white powder from a reaction of acetaldehyde with ammonium sulfide in 60% yield. 

Pyridine has been isolated in the volatile components from cooked beef ( sukiyaki ) in Japan (Shibamoto etal., 1981), fried chicken in the United States (Tang et al., 1983), fried bacon (Ho et al., 1983), Beaufort cheese (Dumont Adda, 1978), black tea aroma (Vitzthum et al., 1975) and coffee aroma (Aeschbacher et al., 1989). 

In some recent research on flavor formation during deep-fat frying at Rutgers University, a number of heterocyclic compounds with long-chain alkyl substituents were found the volatiles of fried chicken (15) and fried potato (16). These included pyridines, thiazoles, oxazoles, trithiolanes and a pyrazine. Only the involvement of lipids or lipid degradation products in the formation of... 

The occurrence of pyridines in food has been reviewed (16). 2-Alky1-pyridines were proposed to form from the corresponding unsaturated n-aldehydes with ammonia upon heat treatment (17, 18). Table I lists pyridines Identified in the volatiles of fried chicken (19) and french fried potatoes (7). 

Chang et al. (42). They Isolated and identified 2,4,5-triinethyl-3-oxazoline in boiled beef. This compound was described as having a "characteristic boiled beef aroma". Mussinan et al. (35) identified oxazolines and no oxazoles in their beef system. Peterson et al. (43) reported on the volatiles of canned beef stew. Both 2,4,5-trimethyloxazole and 2,4,5-trimethyl-3-oxazoline were present. The relative concentration of 2,4,5-trimethyloxazole was medium while for 2,4,5-trlmethyl-3-oxazoline was extra high. Lee et al. (44) identified 2-methyl-3-oxazoline, 2,4-dimethyl-3-oxazoline and 2,4,5-trimethyl-3-oxazoline in the volatiles of roasted peanuts. The latter two 3-oxazollnes were also identified in the volatiles of fried chicken (19). 

The oxidation products of lipids include volatile aldehydes and acids. Therefore, lipids are one of the major sources of flavors in foods. For example, much of the desirable flavors of vegetables such as tomatoes, cucumbers, mushrooms, and peas (Ho and Chen, 1994) fresh fish (Hsieh and Kinsella, 1989), fish oil (Hu and Pan, 2000) and cooked shrimp (Kuo and Pan, 1991 Kuo et al., 1994), as well as many deep-fat fried foods such as French-fried potatoes (Salinas et al., 1994) and fried chicken (Shi and Ho, 1994), are contributed by lipid oxidation. LOX-catalyzed lipid oxidation produces secondary derivatives, e.g., tetradecatrienone, which is a key compound of shrimp (Kuo and Pan, 1991). The major difference between the flavors of chicken broth and beef broth is the abundance of 2,4-decadienal and y-dodeca-lactone in chicken broth (Shi and Ho, 1994). Both compounds are well-known lipid oxidation products. A total of 193 compounds has been reported in the flavor of chicken. Forty-one of them are lipid-derived aldehydes. 

The volatile components of raw chicken breast muscle include mainly carbonyls, thiols, sulfides and alcohols. The major volatile components of fried chicken are similar to volatiles of the meat of farm animals (e.g. common aldehydes, ketones, hydrocarbons and other compounds). Sulfur-containing compounds generated during thermal processing are also important for the flavour of chicken meat. Saturated and unsaturated aldehydes are very important - these are produced easily by oxidation of lipids and manifest negatively in stored poultry meat, which quickly becomes rancid. Feed plays an important role in imparting certain flavour characteristics to poultry meat. 

Source 1-Butanol naturally occurs in white mulberries and papaya fruit (Duke, 1992). Identified as one of 140 volatile constituents in used soybean oils collected from a processing plant that fried various beef, chicken, and veal products (Takeoka et al., 1996). 

Source Furfuryl occurs naturally in yarrow, licorice, sesame seeds, clove flowers, and tea leaves (Duke, 1992). Also detected in barrel-aged red, white, and model wines. Concentrations ranged from 3.5 mg/L in white wine after 55 wk of aging to 9.6 mg/L after 11 wk of aging (Spillman et ah, 1998). Identified as one of 140 volatile constituents in used soybean oils collected from a processing plant that fried various beef, chicken, and veal products (Takeoka et al, 1996). 

The basic fraction of the volatiles identified in the fried pork bundle contained 16 alkylpryazines. Among them, methylpyrazine (nutty, roasted), 2,5-dimethylpyrazine (grilled chicken, roasted peanut), 2,6-dimethylpyrazine (ether-like), 2,3,5-trimethylpyrazine (nutty, roasted) and 2-ethyl-6-methylpyrazine (grassy) were predominant. The combination of these alkylpyrazines may cause the characteristic cooked meat aroma of Chinese fried pork bundle. Quantitative analyses showed that alkylpyrazine formed during the final frying stages, as shown in Table II. 

Acrolein has been identified in foods and food components such as raw cocoa beans, chocolate liquor, souring salted pork, fried potatoes and onions, raw and cooked turkey, and volatiles from cooked mackerel, white bread, raw chicken breast, ripe arctic bramble berries, heated animal fats and vegetable oils, and roasted coffee (Cantoni et al. 1969 EPA 1980, 1985 IARC 1985 Umano and Shibamoto 1987). Sufficient data are not available to establish the level of acrolein typically encountered in these foods. Trace levels of acrolein have been found in wine, whiskey, and lager beer (IARC 1985). Further information regarding the occurrence of acrolein in food and related products is provided by EPA (1980). 

The structure of the food matrix is also known to affect the release of volatile compounds having an impact on flavors and aroma. Changes in flavor result from the interactions of lipid-derived carbonyl compounds by aldolization with the amino groups of proteins. Undesirable flavors are produced when beef or chicken are fried in oxidized fats by the interaction of secondary lipid oxidation... 

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