Analysis And Comparison Of Tastes And Smell Of Different Yellow Feather Chickens And Establishment Of Testing Model

China’s chicken industry consists of two major sectors:white-feathered chicken and yellow-feathered chicken.There are many varieties of yellow-feathered chicken,but there is a lack of unified yellow-feathered chicken flavor evaluation standards.Therefore,it is very important to form a set of standardized yellow-feathered chicken flavor evaluation system for the healthy development of the industry.This study selected 4 local representative yellow-feathered chickens including the Langshan chicken,Luyuan chicken,Wenchang chicken,and Chongren chicken,in order to make the results comparable,egg hatching,feed ratio,feeding conditions are completely unified.The tastes and smell indexes of the 4 selected breeds were measured systematically.A sensory evaluation team was established according to national standards to conduct standard sensory evaluation on the taste and odor of the samples.PLS method was used to analyze the correlation between physical and chemical measurement results and sensory evaluation results to find out the corresponding odor and taste substances that affected sensory evaluation.The regression model has high correlation and good prediction ability.Finally by using Principal Component Analysis（PCA）with the method of Mahalanobis distance to explore the flavor ratings,and use the Python language can produce automatically chicken taste and odor rating and grading computer software,realizes the automatic rating scores and compare different samples,to determine the overall state of the difference between the sample and prediction.This study provided a data basis for the study on the odor of yellow feather chicken from the aspects of machine measurement and sensory assessment,and provided a reference for the evaluation and prediction of the odor of yellow feather chicken.Specific research contents and results are as follows:1.Sensory correlation analysis and Instrumental analysis of smell characteristics of different yellow feather chickensAfter standardized slaughter of 5 yellow-feathered chickens of 4 selected breeds,the brisket and leg meat were extracted and preserved in low temperature（-18℃）.Samples were determined by GC-MS system for volatile substance,and quantitative the samples by using internal standard method.It can be concluded that,the main volatile substances in the chicken including aldehydes,ketones,alcohols and hydrocarbons,and the aldehydes are the main flavour substances,such as hexanal,amyl aldehyde,caprylic aldehyde,It has high content and low flavor threshold.It was found that the smell of Luyuan chicken was the best,while that of Chongren chicken was the worst.The sensory evaluation results showed that the Luyuan chickens also scored the highest in the dimensions of fat taste and hay taste.Partial Least Squares（PLS）is used to extract the variation information of the original data from the tables of independent variables and dependent variables to establish the regression model The connection of the sensory evaluation results and the concentration of the odor substance by PLS,Q²cum=0.936,which proved that the model has a high correlation.The PLS proved that the important sequence of the substance that could have significant effects on sensory evaluation is:Hexenal>Valeraldehyde>Decaldehyde>1-Octene-3-Alcohol>Heptanal>Octenal.2.Sensory correlation analysis and Instrumental analysis of tastes characteristics of different yellow feather chickensAfter standardized slaughtering,take off the breast and leg meat of the 4 selected chickens,cooked the meat and stir it,and preserved in low temperature（-18℃）.The chicken samples stored at-18℃above were determined and analyzed for the types and contents of amino acids,minerals and nucleotides.In terms of amino acids,a total of 15kinds of amino acids were measured,among which phenylalanine and glutamate were relatively abundant and were the main flavor amino acids.In terms of minerals,differences in Ca²⁺,K⁺,Mg²⁺,Na⁺,and PO₄^3-were measured.In terms of nucleotides,GMP,IMP,AMP,Hypoxanthine and Inosine were determined.The results showed that the content of amino acids in Wenchang chicken was higher than that in Luyuan chicken.In the aspect of mineral content,the content of all kinds of Langshan chicken is higher;In terms of nucleotide content,the overall state of Wenchang chicken was the best while that of Luyuan chicken was lower.The sensory evaluation results showed that there was no significant difference between different chicken breeds in terms of sweet taste,and Wenchang chicken had a relatively high sweet taste.In the aspect of saltiness,the Langshan chicken scored higher;In terms of umami taste,Wenchang chicken scored the highest,nearly twice as high as Luyuan chicken.By partial least squares（PLS）set up the connection between the flavor substances concentration and sensory evaluation results,Q²cum=0.993,which proved correlation model is higher,PLS show that the content of mineral elements in samples of salty play a key role,while the content of amino acid and nucleotide part affect the ratings on the sample of the judgement of freshness and sweetness.3.Establishment of chicken flavor prediction and judgment model based on principal component analysis and Mahalanobis distanceThrough the deeper analysis of the smell and taste results,the key factors that can influence the flavor of the product can be concluded.This study used principal component analysis（PCA）to carry out the sample data dimension reduction,then using the Mahalanobis distance contrast similarity between samples,this study defines the concept of"Best sample"as a markov distance calculation reference sample.The Mahalanobis distance value is lower,means the smaller the difference between the samples.In the calculation of Mahalanobis distance,the sample with the smallest Mahalanobis distance is Luyuan chicken,which is 25.69.Wenchang chicken and Langshan chicken followed,with the values of 26.7 and 26.66 respectively,and Chongren chicken had the highest value of28.77.Therefore,it can be concluded that Luyuan chicken is closer to the"Best sample".In terms of taste substance,the nucleotide Mahalanobis distance had little difference among different chicken species.The score of Langshan chicken was better than that of Luyuan chicken.The mineral content is also relatively uniform between the breeds.In terms of amino acid content,there are differences among chicken breeds.Wenchang chicken has obvious advantages over other chicken breeds,while Luyuan chicken has a poor score.Based on Python editing language,the algorithm is imported.The software contains the input control of odor data,the core operation module and the output control.The input sample can be automatically analyzed,and the score and rating can be given finally.