Changes Of Flavor Compounds In Salted Egg Yolk Processing And Preliminary Study On The Causes

In order to explore the formation mechanism of salted egg yolk flavor and expound the main factors affecting the formation of flavor compounds, this thesis focused on the effects of curing time on the main components of egg yolk, free amino acid composition, fatty acid composition and volatile flavor compounds. the result show that:The changes of the main components of egg yolk during the curing process was explored. As the curing time increased, the protein (from 24.80% to 38.90%)and fat content(from 29.07% to 39.86%) showed an increasing trend significantly, while the total sugar content was not obvious ( 0.02 g/100 g ) , water content showed an decreasing trend significantly (from 46.84% to 19.55%). The sensory score of egg yolk continued to rise,reaching twenty-eight days, egg yolk flavor sensory score was relatively stable.Automatic amino acid analyzer was used to analyze the content of 17 kinds of free amino acid, which all showed an increasing trend with the increase of pickling time. From 0 to 7 days, glutamic acid (from 14.76 ?g/g to 20.70 ?g/g) and aspartic acid content(from 12.50 ?g/g to 16.27 ?g/g) increased rapidly. Cysteine content ( from 50.37 ? g/g to58.57 ?g/g) increased rapidly from 7 to 14 days. Except for methionine, the content of other free amino acids increased slowly from 14 to 28 days. From 28 to 35 days, the growth trend of alanine (from 8.61 ?g/g to 14.49 ?g/g ) and leucine ( from 11.93 ?g/g to ?g/g)was more obvious.Fatty acid composition of fresh egg yolk, salted egg yolk and cooked salted egg yolk were determined by gas chromatography-mass spectrometry. The result revealed that the saturated fatty acids were 71.21%, 70.81% and 71.25%, unsaturated fatty acids were 28.43%, 28.54% and 28.49%, respectively. The types of fatty acids were 27, 25 and 27,respectively. Can be seen, the differences of fatty acid content and type were not obvious.The volatile flavor compounds of egg yolk in different salted time were identified by space solid phase microextraction coupled with gas chromatography and electronic nose.Combined with principal component analysis, the results showed that (E)-2-enal,2-methylbutanal, thiophene, 2,3-pentanedione, valeraldehyde,pentan-2-one, pyrazine,3-methyl-1 -butanol, methylbut-2-enoate, hexanal, hexan-2-one, (Z)-3-hexenal,1,4-dichlorobenzene,Cymene,heptyl mercaptan,these volatile flavoring substances were detected only in cooked salted duck egg yolk, so that egg yolk presented its unique flavor.Comprehensive analyze the changes of egg yolk composition in processing and the souse of characteristic flavor compounds, conclusion was obtained: Amino acid and fatty acid, as precursors of flavor, made important contribution to the flavor of egg yolk. Egg yolk flavor was cooperative reaction results of Manard reaction and lipids oxidation.