| Meat flavor is mainly produced from the raw meat water-soluble lower molecule compounds and fatty acids during heating.The non-volatile and volatile components constitute the meat flavor with microscale,diversity and complexity,which is a leading factor determining the meat quality and purchasing decision of consumer.There are many high-quality local chicken species in China which are suitable to be used for traditional Chinese braising,boiling and other wet processing methods for cooking.It retains chicken original taste and is rich in nutritional value.However,few studies have focused on the flavor compounds of different Chinese high-quality local chicken breeds in relation to age.Thus,the aim of this study was to evaluate the chemical composition of precursor flavor substance of Wuding chicken,YanJin silky fowl chicken and Da Weishan miniature chicken with the different age,and investigated the flavor compound difference on metabolomic of three chicken soups after cooking.Meanwhile,the flavor compounds of selected Cobb and Digao chickens were compared with the three local Chinese chicken.The results are as follows:1.Metabolic characterization of Chinese chicken meat with different ageThe aim of this chapter was to evaluate the chemical composition of precursor flavor substance of Wuding chicken,YanJin silky fowl chicken and Da Weishan miniature chicken with the age of 110,140,170,200,230 and 300 days.Compared with other 5 periods,the total metabolite content was increased with the age and significantly higher in 300 d for the chicken breast and leg meat(P<0.05).The 57 metabolites were unambiguously identified from these three chicken meat.Organic acid and small peptides were the two most metabolites for the chicken breast and leg meat(P<0.05).The most abundant metabolites were lactate,creatine,anserine and carnosine.The total concentration of metabolites showed a significant difference in each chicken breed and period.Alanine,aspartate and glutamate metabolism,purine metabolism,glycine,serine and threonine metabolism and taurine and hypotaurine metabolism were the main metabolic pathways for the Wuding chicken meat flavor.2.Comparison of meat fatty acid composition of three Chinese chicken breed with different ageThis chapter evaluated the fatty acid composition changes of Wuding chicken,YanJin silky fowl and Da Weishan miniature chickens with the age of 110,140,170,200,230 and 300 days.Totally 28 fatty acids from chicken breast and leg meat were identified and quantified.The fatty acid contents showed significant differences among different breeds of chickens that were raised for six different periods of age.The highest content of fatty acids in the breast and leg meat was detected from 300 d and then 110 d of age for the three breeds of chicken(P<0.05).The changes of concentrations of fatty acids were not stable and general tendency was the decrease during the 140 d to 230 d of age.The composition of fatty acids of breast meat was significantly lower than leg meat in three chicken breeds across different ages.The highest total fatty acids were found in Da Weishan miniature breast and leg meat with 300 d(P<0.05),which were 62.48 and 79 mg/g respectively.3.Flavor compound characterization of broiler Chinese local chicken soup during stewingEffects of stewing time(2,2.5 and 3 h)on the levels of concentration of metabolites were measured.The stewing time significantly effected the chicken soup concentration of metabolites,which increased with the stewing time.For the different stewing time,the lactate,creatine,IMP,taurine,anserine and carnosine showed a significant difference.The top abundant metabolites were lactate,creatine and carnosine in the three chicken soups(P<0.05).The top abundant metabolites were found in 3 h Wuding chicken soup(P<0.05).Totally 16 fatty acids from Wuding chicken,YanJin silky fowl and Da Weishan miniature chicken soup were identified and quantified.The content of unsaturated fatty acid was higher than the saturated fatty acids in chicken soup,and the total fatty acids increased with the stewing time.However,the total fatty acids of different chicken breed showed no significant difference among different stewing time.4.Volatility flavor compound characterization of broiler Chinese chicken soup during stewingThe present chapter investigated the effects of stewing time(2,2.5,3 h)on volatile compounds of Wuding chicken soup.The 34 volatile compounds were unambiguously identified including 21 identified through olfactometry.After stewing 2 h,the variety and concentration of volatile compounds decreased dramatically(P<0.01).Trans-2-nonenal,(E,E)-2,4-decedienal,2-undecenal,(E,E)-2,4-nonadienaldehyde,2-pentylfuran and 1-octen-3-ol were the main volatile compounds of the Wuding chicken soup.5.Comparison of flavor compounds between Chinese local chicken and broiler chickenThe object of this chapter was to compare the flavor compound difference between the typical broiler chicken(Cobb and Digao chicken)and Chinese local chicken(Wuding chicken,YanJin silky fowl chicken and Da Weishan miniature chicken).The 53 metabolites were unambiguously identified from Cobb and Digao chicken.The PLS-DA scores plot showed that the metabolites were significantly different between the typical broiler chicken and Chinese local chicken.Specifically,compared with Cobb and Digao chicken,anserine concentration was 4 to 5 times,carnosine was 4 to 6 times,creatine was 6 times,and IMP was 3 to 6 times in Chinese local chicken meat.For these five specie chickens,compared with the breast meat,the concentration of free aminol acids was significantly higher in leg meat(P<0.05),and the total amount of free aminol acids was higher in Chinese local chicken(P<0.05).For the two types chicken soup,the PLS-DA scores plot showed that the metabolites were significantly different,and the total amount of water-soluble compounds was higher in the typical broiler chicken soup.Lactate,acetone,creatine and anserine were the main different metabolites(P<0.05).Totally 19 fatty acids of chicken breast and leg meat were identified and quantified from Cobb and Digao chicken with slaughter age.Compared with 140 d Wuding chicken,YanJin silky fowl chicken and Da Weishan miniature chicken,C24;0 was not detected in Cobb and Digao chicken meat,and the saturated fatty acid,unsaturated fatty acid and total fatty acid were significant lower(P<0.05).The total fatty acids increased with the stewing time in the chicken soup and the top total fatty acid concentration detected from 3 h Digao soup(P<0.05).The DHA was not found from Cobb and Digao chicken soups.The similar variety volatile compounds were found from Wuding,Cobb and Digao chicken soup.However,the concentration and proportion of compounds was different.The concentration of volatile compounds from 2 h Wuding chicken soup was 4 to 6 times higher than 2 h Cobb and Digao chicken soups(P<0.05).The main volatile compounds were aldehydes in 2 h Wuding chicken soup,accounting for 75.19%of total volatile compound.For the 2 h Cobb and Digao chicken soups,the hydrocarbons were the main compound,which took up 54.83%and 50%respectively.Thus the type and concentration of aldehydes could have a major effect on the chicken soup.In summary the total metabolite content and the total fatty acid were increased with the age.Compared with breast meat,the total fatty acid of Wuding chicken,YanJin silky fowl chicken and Da Weishan miniature chicken were higher in leg meat.Alanine,aspartate and glutamate metabolism,purine metabolism,glycine,serine and threonine metabolism and taurine and hypotaurine metabolism were the main metabolic pathways for the Wuding chicken meat flavor.During the cooking process,the stewing time significantly affected the chicken soup concentration of metabolites,which increased with the stewing time.Compared with the typical broiler chicken,the metabolites were significant higher in Chinese local chicken meat(P<0.05),and the type and concentration of flavor substances was the main factors contributing to the difference between the two type soups. |
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