Studies On The Eating Quality Of Soft-boiled Chicken Made From Hot Fresh,Chilled And Frozen Chicken

China consumed the second most chicken of any nation in 2017 which was up to 11.7 million tons.Soft-boiled chicken is one of the traditional low temperature meat products in our nation and is famous for its delicious flavor and tender meat.Hot fresh chicken was used as the material to make soft-boiled chicken in the traditional method.However,to reduce the outbreaks of animal influenza,such as the outbreak of the H7N9 strain in 2013,live poultry markets have been restricted in China.It resulted in the consumption of hot fresh chicken restricted.Meanwhile the consumption ratio of chilled and frozen chicken increased.But many of the consumers still bought hot fresh chicken to make soft-boiled chicken,but there have been no rigorous studies to support then.So this study aimed to investigat the possilbility of using chilled and frozen chicken to replace hot fresh chicken to cook soft-boiled chicken.This study was first to investigate the differences in flavor precursors of hot fresh,chilled and fr-ozen raw chicken and inferred their effects on flavor.Based on the result of chapter one,the content of volatile and taste compounds of soft-boiled chicken made from hot fresh,chilled and frozen chicken was detected and compared.Then differences within treatments and the reasons responsible for them were discussed.Finally,the texture,ultrastructure and in vitro digestibility of soft-boiled chicken of all treatments are evaluated.The main contents are as follows:1.Differences in flavor precursors of hot fresh,chilled and frozen chickenXue shan chicken(hot fresh 1,2,4 h,chilled 24,36,48,60 h,frozen 7,30,60,90 d)was used and the reducing sugar,fatty acids composition,fr-ee amino acids,nucleotide,thiamine contents and pH were investigated.The pH value of hot fresh 1 h treatment was significantly higher than the other treatments(P<0.05).There were no significant differences among chilled and frozen treatments in pH values which range from 5.41-5.54(P>0.05).Meanwhile hot fresh 4 h had lowest pH value which was 5.30.Hot fresh 1,4 h,frozen 7 d group and 4 chilled treatments had no significant differences on IMP value(P>0.05).The chilled and frozen groups had higher free amino acid contents than hot fresh groups.Hot fresh 4 h,frozen 7,30 d and chilled 24,36,60 h treatments had no significant differences on reducing sugar contents(P>0.05).There were also no significant differences among most of the treatments in PUFA values(P>0.05).The thiamine contents in frozen treatments were significantly higher than hot fresh and chilled treatments(P<0.05)and hot fresh treatments had lower thiamine values than chilled treatments.2.Flavor of soft-boiled chicken made from hot fresh,chilled and frozen chickenXue shan chicken(hot fresh 1,2,4 h,ehilled 24,36,48,60 h,frozen 7,30,60,90 d)was used to make soft-boiled chicken using a traditional method.The volatile flavor and taste compounds(organic acids,free amino acids,nucleotides)and pH were investigated.While sensory evaluation were also conducted.There were no significant differences in IMP and total free amino acids contents among hot fresh 2,4 h and 4 chilled treatments(P>0.05)and chilled treatments had higher major volatile compound values and succinic acid contents than hot fresh 2,4 h treatments.Meanwhile,the trend of IMP and free amino acids contents were consistent with the results of chapter 1.Hot fresh 1 h treatment had significant higher contents of IMP than 4 chilled treatments(P<0.05),but it had lower volatile compound values.Frozen 60 and 90 d treatments had lower 2-pentylfuran,organic acids,IMP and total free amino acids values but they had significant higher content of hexanal than hot fresh and chilled treatments(P<0.05).There were no significant differences in major volatile compounds like aldehydes and 2-pentyl furan and IMP,total free amino acids contents among treatments which chickens stored frozen for 7 d,30d and hot fresh 2,4 h or chilled treatments(P>0.05).The results of sensory evaluation were consistent with the results of volatile and taste values.3.Quality,ultrastructure and in vitro digestibility of soft-boiled chicken made fromhot fresh,chilled and frozen chickenXue shan chicken(hot fresh 1,2,4 h,ehilled 24,36,48,60 h,frozen 7,30,60,90 d)was used to make soft-boiled chicken using a traditional method.The color,tenderness,water holding capacity,texture,ultrastructure and in vitro digestibility of soft-boiled chicken made from hot fresh,chilled and frozen chicken were investigated.Hot fresh 1 h had highest L*value in all treatments and there were no significant differences among the other treatments in L*and b*values(P>0.05).Chilled treatments had better water holding capacity and tender than hot fresh groups.Frozen groups had no significant differences in water holding capacity with hot fresh groups(P>0.05)and frozen 7 d group was tender than hot fresh treatments.There were no significant differences among hot fresh 2,4 h,4 chilled and frozen 7 d treatments(P>0.05)in texture values which were better than hot fresh 1,2 h and frozen 30,60,90 d treatments.The fiber diameters of chilled treatments were shorter than hot fresh and frozen treatments which means they were tender.Moreover,the digestibility of chilled and frozen treatments were higher than hot fresh groups.The results of sensory evaluation were consistent with the results of color,water holding capacity,texture and tenderness.Overall,chilled and short time(7,30 d)frozen chicken could replace hot fresh chicken to make soft-boiled chicken in flavor precursor contents(IMP,PUFA,free amino acids,reducing sugar,thiamine),major volatile compounds(aldehydes and furans),major taste compounds(IMP,total free amino acids),skin color,tenderness,water holding capacity,texture and in vitro digestibility and these results provided a basis for commercial processing of the product.