| Chicken is one of the most important foods in people's daily life. It can provide the protein, fat and vitamin, which is more superior quality. Comparing with the beef and the pork, the quality of the chicken protein is higher, the fat content is lower. In addition, it enriches to contain all-having to amino acids in the chicken protein. The content and the amino acids table type in the egg or milk are extremely alike. Therefore it is the source of protein for superior quality. Chicken will decay during storage,which can decrease its nutrition, change the tasting, produce poisonous substance, and do harm to the consumer. The fresh degree of chicken is significant in its quality checking, and more and more people recognize its importance. The checking method and means has improved quickly. Fresh degree checking includes sensory, physical chemical and microorganism checking. More attention has been paid to the physical chemical checking in this thesis. After analyzing the references and the decay mechanism of meat,7 physical chemical indexes (elasticity ,TVB-N examination ,pH measurement, acidity-oxidizing ability coefficient measurement, catalase reaction, protein precipitating reaction, and hydrogen sulfide examination) was selected to analyze chicken fresh degree according to the condition of the laboratory. Each index was determined at different temperature (0℃,2℃,4℃,6℃,8℃) to study the changing rule of the index with time and TVB-N, and provide a basis for further study. Pertinence between the index and TVB-N was set and the possibility of checking chicken fresh degree by elasticity was determined by regress analysis.The main contents are as followed:1.Analysis of each the physical chemical index at different temperature:Chicken was stored at 0℃,2℃,4℃,6℃,8℃,the index was determined every (1)The TVB-N increased with time. The regression equations(P≤0.01)are as followed: x2=6.728811+0.081353x1-0.000134x12+0.000001x13 (1) x2=7.536503+0.049512x1+0.000348x12-0.000001x13 (2) x2=7.247475+0.103360x1-0.000807x12+ 0.000005x13 (3) x2=7.954545-0.004482x1+0.001420x12-0.000004 x13 (4) x2=7.416667+0.131366x1-0.000217x12+0.000003x13 (5) where: x1-time;x2- TVB-N(mg/100g)The regression equations showed that the time of the storage when the TVB-N is over 15mg/100g.(2) There was an obviously relativity between pH and TVB-N. Polynomial fitting equation was obtained by least square method. Chicken was stored at 0℃,2℃,4℃,6℃,8℃,The regression equations of the relativity between pH and the total volatile basic nitrogen are as followed: x2=7.544034-0.241383x1+0.017431x12-0.000351x13 (6) x2=6.438955+0.031660x1-0.001641x12+ 0.000040x13 (7) x2=6.782423-0.057900x1+0.004768x12-0.000083x13 (8) x2=7.156628-0.126947x1+0.007275x12-0.00011x13 (9) x2=6.508906+0.025920x1-0.000993x12+ 0.000015 x13 (10) where: x1- TVB-N(mg/100g);x2- pHThe pH at which the TVB-N is 15mg/100g was calculated by this equation,and then the pH range could be determined when TVB-N is over 15mg/100g,that is beyond national criterion.(3)The changed regularly during storage, and had obvious relativity with TVB-N(F test). Chicken was stored at 0℃,2℃,4℃,6℃,8℃,The regression equations are as followed x2=-0.406787+0.171691x1-0.011964*12+ 0.000237x13 (11) x2=-0.457974+0.163183x1-0.010199x12+ 0.000182x13 (12) x2=0.085219+0.056549x1-0.004327x12+ 0.000082x13 (13) x2=-0.081489+0.087152x1-0.005562x12+0.000096x13 (14) x2=-0.156085+0.082967x1-0.005035x12+0.000085x13 (15) where: x1- TVB-N(mg/100g);x2- acidity-oxidizing ability coefficientAccording to the equations, when the acidity-oxidizing ability coefficient is bellowed 0.24, chicken has been unfresh. (4)H2S reaction, protein precipitating reaction and catalase test were used to qualifiedly determine chicken fresh degree. The first test can be used to judge weather chicken decayed or not because The phenomenon of H2S isn't obvious until the meat is go bad with depth;The second and the third reaction can be used to determine chicken fresh degree because of their sensitivity,and the new quantitative method should be explored.2.Chicken leg elasticity test was done by using Computerized Numerical Control electric omnipotent tester at 4℃,and the curve was analyzed by Hua-long software. The relationship between variation distance after oppression and time , between variation distance and TVB-N were obtained; and the relativity between the most action and time, between the most action and TVB-N were also obtained. According to the analysis of the datas, with the increase of storage time variation distance and the most action decreased. Regression analysis showed that these two indexes can be used to judge chicken fresh degree.Elasticity and TVB-N was determined every 24hs.The conclusions are as followed:(1)With the increase of storage time variation distance and the most action decreased, and there is relationship between variation distance of A and B and TVB-N, and between the most action and TVB-N . Regression analysis showed that these two indexes can be used to judge chicken fresh degree.(2)The regression analysis of showed that variation rate of A liner changed with time,and decrease with time. So A is more proper as a point to determine elasticity than B.The innovation of the thesis:Computerized Numerical Control electric omnipotent tester was used to determine chicken elasticity. According to the calculation and the analyze ,it can be inferred that the elasticity can judge a fresh degree of chicken quantitatively,the fixed point of chicken leg elasticity testing was determined at the same time, which increase the accuracy of chicken fresh degree test.Through analyzing each physiochemical index,the regression equation of TVB-N and time, acidity-oxidizing ability coefficient, which provide data base for analyzing chicken fresh degree.Totally speaking, the thesis detailed the variation of chicken fresh degree at different temperature. Quantitatively analysis provides a great deal of data base for chicken fresh degree detesting. Quantitatively analysis of chicken leg elasticity showed that fresh degree can be reflected by elasticity, and the change of variation distance with time can accurately reflect the variation of fresh degree.
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